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  • 1.
    Argillander, Joakim
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Alarcon, Alvaro
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Bao, Chunxiong
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Nanjing Univ, Peoples R China.
    Kuang, Chaoyang
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Science and Technology, Laboratory of Organic Electronics.
    Lima, Gustavo
    Univ Concepcion, Chile.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Xavier, Guilherme B.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Quantum random number generation based on a perovskite light emitting diode2023In: Communications Physics, E-ISSN 2399-3650, Vol. 6, no 1, article id 157Article in journal (Refereed)
    Abstract [en]

    True random number generation is not thought to be possible using a classical approach but by instead exploiting quantum mechanics genuine randomness can be achieved. Here, the authors demonstrate a certified quantum random number generation using a metal-halide perovskite light emitting diode as a source of weak coherent polarisation states randomly producing an output of either 0 or 1. The recent development of perovskite light emitting diodes (PeLEDs) has the potential to revolutionize the fields of optical communication and lighting devices, due to their simplicity of fabrication and outstanding optical properties. Here we demonstrate that PeLEDs can also be used in the field of quantum technologies by implementing a highly-secure quantum random number generator (QRNG). Modern QRNGs that certify their privacy are posed to replace classical random number generators in applications such as encryption and gambling, and therefore need to be cheap, fast and with integration capabilities. Using a compact metal-halide PeLED source, we generate random numbers, which are certified to be secure against an eavesdropper, following the quantum measurement-device-independent scenario. The obtained generation rate of more than 10 Mbit s(-1), which is already comparable to commercial devices, shows that PeLEDs can work as high-quality light sources for quantum information tasks, thus opening up future applications in quantum technologies.

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  • 2.
    Bai, Sai
    et al.
    Zhejiang University, Peoples R China .
    Cao, Motao
    Zhejiang University, Peoples R China .
    Jin, Yizheng
    Zhejiang University, Peoples R China Zhejiang University, Peoples R China Zhejiang University, Peoples R China .
    Dai, Xinliang
    Zhejiang University, Peoples R China .
    Liang, Xiaoyong
    Zhejiang University, Peoples R China .
    Ye, Zhizhen
    Zhejiang University, Peoples R China Zhejiang University, Peoples R China .
    Li, Min
    Zhejiang University, Peoples R China .
    Cheng, Jipeng
    Zhejiang University, Peoples R China .
    Xiao, Xuezhang
    Zhejiang University, Peoples R China .
    Wu, Zhongwei
    Soochow University, Peoples R China .
    Xia, Zhouhui
    Soochow University, Peoples R China .
    Sun, Baoquan
    Soochow University, Peoples R China .
    Wang, Ergang
    Chalmers, Sweden .
    Mo, Yueqi
    S China University of Technology, Peoples R China .
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Low-Temperature Combustion-Synthesized Nickel Oxide Thin Films as Hole-Transport Interlayers for SolutionProcessed Optoelectronic Devices2014In: Advanced Energy Materials, ISSN 1614-6832, E-ISSN 1614-6840, Vol. 4, no 6Article in journal (Refereed)
    Abstract [en]

    A method to deposit NiOx thin films by employing combustion reactions is reported and a low processing temperature of 175 °C is demonstrated. The resulting NiOx films exhibit high work functions, excellent optical transparency, and flat surface features. The NiOx thin films are employed as hole-transport interlayers in organic solar cells and polymer light-emitting diodes, exhibiting superior electrical properties

  • 3.
    Bai, Sai
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Univ Oxford, England.
    Da, Peimei
    Univ Oxford, England.
    Li, Cheng
    Univ Bayreuth, Germany; Xiamen Univ, Peoples R China.
    Wang, Zhiping
    Univ Oxford, England.
    Yuan, Zhongcheng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Fu, Fan
    Empa-Swiss Federal Laboratories for Materials Science and Technology, Duebendorf, Switzerland.
    Kawecki, Maciej
    Empa, Switzerland; Univ Basel, Switzerland.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Sakai, Nobuya
    Univ Oxford, England.
    Wang, Jacob Tse-Wei
    CSIRO Energy, Australia.
    Huettner, Sven
    Univ Bayreuth, Germany.
    Buecheler, Stephan
    Empa Swiss Fed Labs Mat Sci and Technol, Switzerland.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Univ Oxford, England.
    Snaith, Henry J.
    Univ Oxford, England.
    Planar perovskite solar cells with long-term stability using ionic liquid additives2019In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 571, no 7764, p. 245-250Article in journal (Refereed)
    Abstract [en]

    Solar cells based on metal halide perovskites are one of the most promising photovoltaic technologies(1-4). Over the past few years, the long-term operational stability of such devices has been greatly improved by tuning the composition of the perovskites(5-9), optimizing the interfaces within the device structures(10-13), and using new encapsulation techniques(14,15). However, further improvements are required in order to deliver a longer-lasting technology. Ion migration in the perovskite active layer-especially under illumination and heat-is arguably the most difficult aspect to mitigate(16-18). Here we incorporate ionic liquids into the perovskite film and thence into positive-intrinsic-negative photovoltaic devices, increasing the device efficiency and markedly improving the long-term device stability. Specifically, we observe a degradation in performance of only around five per cent for the most stable encapsulated device under continuous simulated full-spectrum sunlight for more than 1,800 hours at 70 to 75 degrees Celsius, and estimate that the time required for the device to drop to eighty per cent of its peak performance is about 5,200 hours. Our demonstration of long-term operational, stable solar cells under intense conditions is a key step towards a reliable perovskite photovoltaic technology.

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  • 4.
    Bai, Sai
    et al.
    Zhejiang University, Peoples R China.
    He, Shasha
    Zhejiang University, Peoples R China.
    Jin, Yizheng
    Zhejiang University, Peoples R China.
    Wu, Zhongwei
    Soochow University, Peoples R China.
    Xia, Zhouhui
    Soochow University, Peoples R China.
    Sun, Baoquan
    Soochow University, Peoples R China.
    Wang, Xin
    Zhejiang University, Peoples R China.
    Ye, Zhizhen
    Zhejiang University, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Shao, Shuyan
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Electrophoretic deposited oxide thin films as charge transporting interlayers for solution-processed optoelectronic devices: the case of ZnO nanocrystals2015In: RSC Advances, E-ISSN 2046-2069, Vol. 5, no 11, p. 8216-8222Article in journal (Refereed)
    Abstract [en]

    A promising fabrication method of electron transporting interlayers for solution-processed optoelectronic devices by electrophoretic deposition (EPD) of colloidal zinc oxide (ZnO) nanocrystals was demonstrated. A low voltage of 3-5 V and a short deposition time of 40 s at room temperature were found to be sufficient to generate dense and uniform ZnO thin films. The EPD ZnO nanocrystal films were applied as ETLs for inverted organic solar cell and polymer light emitting diodes (PLEDs). By optimizing the EPD processing of ZnO nanocrystal electron transporting layers (ETLs), inverted organic solar cells based on [3,4-b]-thiophene/benzodithiophene (PTB7): [6-6]-phenyl-C71-butyric acid methyl ester (PC71BM) and poly(3-hexylthiophene) (P3HT): [6-6]-phenyl-C-61-butyric acid methyl ester (PC61BM) with an average PCE of 8.4% and 4.0% were fabricated. In combination with the PLEDs and flexible devices results, we conclude that the EPD processed ZnOnanocrystal thin films can serve as high quality ETLs for solution-processed optoelectronic devices.

  • 5.
    Bai, Sai
    et al.
    Zhejiang University, Peoples R China; Zhejiang University, Peoples R China.
    Jin, Yizheng
    Zhejiang University, Peoples R China; Zhejiang University, Peoples R China.
    Liang, Xiaoyong
    Zhejiang University, Peoples R China; Zhejiang University, Peoples R China.
    Ye, Zhizhen
    Zhejiang University, Peoples R China; Zhejiang University, Peoples R China.
    Wu, Zhongwei
    Soochow University, Peoples R China.
    Sun, Baoquan
    Soochow University, Peoples R China.
    Ma, Zaifei
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Tang, Zheng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Wang, Jianpu
    Nanjing Technical University, Peoples R China.
    Wuerfel, Uli
    Fraunhofer Institute Solar Energy Syst ISE, Germany; University of Freiburg, Germany.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Ethanedithiol Treatment of Solution-Processed ZnO Thin Films: Controlling the Intragap States of Electron Transporting Interlayers for Efficient and Stable Inverted Organic Photovoltaics2015In: Advanced Energy Materials, ISSN 1614-6832, E-ISSN 1614-6840, Vol. 5, no 5, p. 1401606-Article in journal (Refereed)
    Abstract [en]

    The surface defects of solution-processed ZnO films lead to various intragap states. When the solution-processed ZnO films are used as electron transport interlayers (ETLs) in inverted organic solar cells, the intragap states act as interfacial recombination centers for photogenerated charges and thereby degrade the device performance. Here, a simple passivation method based on ethanedithiol (EDT) treatment is demonstrated, which effectively removes the surface defects of the ZnO nanocrystal films by forming zinc ethanedithiolates. The passivation by EDT treatment modulates the intragap states of the ZnO films and introduces a new intragap band. When the EDT-treated ZnO nanocrystal films are used as ETLs in inverted organic solar cells, both the power conversion efficiency and stability of the devices are improved. The control studies show that the solar cells with EDT-treated ZnO films exhibit reduced charge recombination rates and enhanced charge extraction properties. These features are consistent with the fact that the modulation of the intragap states results in reduction of interfacial recombination as well as the improved charge selectivity and electron transport properties of the ETLs. It is further demonstrated that the EDT treatment-based passivation method can be extended to ZnO films deposited from sol-gel precursors.

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  • 6.
    Bai, Sai
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Univ Oxford, England.
    Sakai, Nobuya
    Univ Oxford, England.
    Zhang, Wei
    Univ Oxford, England; Univ Lincoln, England.
    Wang, Zhiping
    Univ Oxford, England.
    Wang, Jacob T.-W.
    Univ Oxford, England.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Univ Oxford, England.
    Snaith, Henry J.
    Univ Oxford, England.
    Reproducible Planar Heterojunction Solar Cells Based on One-Step Solution-Processed Methylammonium Lead Halide Perovskites2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 1, p. 462-473Article in journal (Refereed)
    Abstract [en]

    Metal halide perovskites have been demonstrated as one of the most promising materials for low-cost and high-performance photovoltaic applications. However, due to the susceptible crystallization process of perovskite films on planar substrates and the high sensitivity of the physical and optoelectronic nature of the internal interfaces within the devices, researchers in different laboratories still experience poor reproducibility in fabricating efficient perovskite solar cells with planar heterojunction device structures. In this method paper, we present detailed information on the reagents, equipment, and procedures for the fabrication of planar perovskite solar cells in both "regular" n-i-p and "inverted" p-i-n architectures based on one-step solution-processed methylammonium lead triiodide (MAPbI(3)) perovskite films. We discuss key parameters affecting the crystallization of perovskite and the device interfaces. This method paper will provide a guideline for the reproducible fabrication of planar heterojunction solar cells based on MAPbI3 perovskite films. We believe that the shared experience on MA-based perovskite films and planar solar cells will be also useful for the optimization process of perovskites with varied compositions, and other emerging perovskite-based optoelectronic devices.

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  • 7.
    Bai, Sai
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Yuan, Zhongcheng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Colloidal metal halide perovskite nanocrystals: synthesis, characterization, and applications2016In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 4, no 18, p. 3898-3904Article in journal (Refereed)
    Abstract [en]

    Colloidal metal halide perovskite nanocrystals (NCs) have emerged as promising materials for optoelectronic devices and received considerable attention recently. Their superior photoluminescence (PL) properties provide significant advantages for lighting and display applications. In this Highlight, we discuss recent developments in the design and chemical synthesis of colloidal perovskite NCs, including both organic-inorganic hybrid and all inorganic perovskite NCs. We review the excellent PL properties and current optoelectronic applications of these perovskite NCs. In addition, critical challenges that currently limit the applicability of perovskite NCs are discussed, and prospects for future directions are proposed.

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  • 8.
    Bai, Yang
    et al.
    Beijing Univ Chem Technol, Peoples R China.
    Zhang, Ze
    Beijing Univ Chem Technol, Peoples R China.
    Zhou, Qiuju
    Xinyang Normal Univ, Peoples R China.
    Geng, Hua
    Capital Normal Univ, Peoples R China.
    Chen, Qi
    Beijing Univ Chem Technol, Peoples R China.
    Kim, Seoyoung
    Ulsan Natl Inst Sci & Technol UNIST, South Korea.
    Zhang, Rui
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zhang, Cen
    Beijing Univ Chem Technol, Peoples R China.
    Chang, Bowen
    Beijing Univ Chem Technol, Peoples R China.
    Li, Shangyu
    Beijing Univ Chem Technol, Peoples R China.
    Fu, Hongyuan
    Beijing Univ Chem Technol, Peoples R China.
    Xue, Lingwei
    Beijing Univ Chem Technol, Peoples R China.
    Wang, Haiqiao
    Beijing Univ Chem Technol, Peoples R China.
    Li, Wenbin
    Zhengzhou Univ, Peoples R China; Zhengzhou Univ, Peoples R China.
    Chen, Weihua
    Zhengzhou Univ, Peoples R China; Zhengzhou Univ, Peoples R China.
    Gao, Mengyuan
    Tianjin Univ, Peoples R China.
    Ye, Long
    Tianjin Univ, Peoples R China.
    Zhou, Yuanyuan
    Hong Kong Baptist Univ, Peoples R China; Hong Kong Baptist Univ, Peoples R China.
    Ouyang, Yanni
    Hong Kong Baptist Univ, Peoples R China; Hong Kong Baptist Univ, Peoples R China.
    Zhang, Chunfeng
    Nanjing Univ, Peoples R China; Nanjing Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Yang, Changduk
    Ulsan Natl Inst Sci & Technol UNIST, South Korea.
    Li, Yongfang
    Chinese Acad Sci, Peoples R China.
    Zhang, Zhi-Guo
    Beijing Univ Chem Technol, Peoples R China.
    Geometry design of tethered small-molecule acceptor enables highly stable and efficient polymer solar cells2023In: Nature Communications, E-ISSN 2041-1723, Vol. 14, no 1, article id 2926Article in journal (Refereed)
    Abstract [en]

    With the power conversion efficiency of binary polymer solar cells dramatically improved, the thermal stability of the small-molecule acceptors raised the main concerns on the device operating stability. Here, to address this issue, thiophene-dicarboxylate spacer tethered small-molecule acceptors are designed, and their molecular geometries are further regulated via the thiophene-core isomerism engineering, affording dimeric TDY-alpha with a 2, 5-substitution and TDY-beta with 3, 4-substitution on the core. It shows that TDY-alpha processes a higher glass transition temperature, better crystallinity relative to its individual small-molecule acceptor segment and isomeric counterpart of TDY-beta, and amore stablemorphology with the polymer donor. As a result, the TDY-alpha based device delivers a higher device efficiency of 18.1%, and most important, achieves an extrapolated lifetime of about 35000 hours that retaining 80% of their initial efficiency. Our result suggests that with proper geometry design, the tethered small-molecule acceptors can achieve both high device efficiency and operating stability.

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  • 9.
    Bakulin, Artem A.
    et al.
    FOM Institute AMOLF, Netherlands; University of Cambridge, England.
    Xia, Yuxin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Bakker, Huib J.
    FOM Institute AMOLF, Netherlands.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Morphology, Temperature, and Field Dependence Separation in High-Efficiency Solar Cells Based on Polyquinoxaline Copolymer2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 8, p. 4219-4226Article in journal (Refereed)
    Abstract [en]

    Charge separation and recombination are key processes determining the performance of organic optoelectronic devices. Here we combine photoluminescence and photovoltaic characterization of organic solar cell devices with ultrafast multipulse photocurrent spectroscopy to investigate charge generation mechanisms in the organic photovoltaic devices based on a blend of an alternating polyquinoxaline copolymer with fullerene. The combined use of these techniques enables the determination of the contributions of geminate and bimolecular processes to the solar cell performance. We observe that charge separation is not a temperature-activated process in the studied materials. At the same time, the generation of free charges shows a dear external field and morphology dependence. This indicates that the critical step of charge separation involves the nonequilibrium state that is formed at early times after photoexcitation, when the polaronic localization is not yet complete. This work reveals new aspects of molecular level charge dynamics in the organic light-conversion systems.

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  • 10.
    Bao, Chunxiong
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Nanjing Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Physics of defects in metal halide perovskites2022In: Reports on progress in physics (Print), ISSN 0034-4885, E-ISSN 1361-6633, Vol. 85, no 9, article id 096501Article, review/survey (Refereed)
    Abstract [en]

    Metal halide perovskites are widely used in optoelectronic devices, including solar cells, photodetectors, and light-emitting diodes. Defects in this class of low-temperature solution-processed semiconductors play significant roles in the optoelectronic properties and performance of devices based on these semiconductors. Investigating the defect properties provides not only insight into the origin of the outstanding performance of perovskite optoelectronic devices but also guidance for further improvement of performance. Defects in perovskites have been intensely studied. Here, we review the progress in defect-related physics and techniques for perovskites. We survey the theoretical and computational results of the origin and properties of defects in perovskites. The underlying mechanisms, functions, advantages, and limitations of trap state characterization techniques are discussed. We introduce the effect of defects on the performance of perovskite optoelectronic devices, followed by a discussion of the mechanism of defect treatment. Finally, we summarize and present key challenges and opportunities of defects and their role in the further development of perovskite optoelectronic devices.

  • 11.
    Bao, Chunxiong
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Shenzhen Univ, Peoples R China.
    Xu, Weidong
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Nanjing Tech Univ NanjingTech, Peoples R China.
    Yang, Jie
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Shenzhen Univ, Peoples R China.
    Bai, Sai
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Teng, Pengpeng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Nanjing Univ Aeronaut and Astronaut, Peoples R China.
    Yang, Ying
    Nanjing Univ Aeronaut and Astronaut, Peoples R China.
    Wang, Jianpu
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Zhao, Ni
    Chinese Univ Hong Kong, Peoples R China.
    Zhang, Wenjing
    Shenzhen Univ, Peoples R China.
    Huang, Wei
    Nanjing Tech Univ NanjingTech, Peoples R China; NPU, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Bidirectional optical signal transmission between two identical devices using perovskite diodes2020In: NATURE ELECTRONICS, ISSN 2520-1131, Vol. 3, no 3, p. 156-164Article in journal (Refereed)
    Abstract [en]

    A solution-processed perovskite diode that functions as both optical transmitter and receiver can be used to build a monolithic pulse sensor and a bidirectional optical communication system. The integration of optical signal generation and reception into one device-thus allowing a bidirectional optical signal transmission between two identical devices-is of value in the development of miniaturized and integrated optoelectronic devices. However, conventional solution-processable semiconductors have intrinsic material and design limitations that prevent them from being used to create such devices with a high performance. Here we report an efficient solution-processed perovskite diode that is capable of working in both emission and detection modes. The device can be switched between modes by changing the bias direction, and it exhibits light emission with an external quantum efficiency of over 21% and a light detection limit on a subpicowatt scale. The operation speed for both functions can reach tens of megahertz. Benefiting from the small Stokes shift of perovskites, our diodes exhibit a high specific detectivity (more than 2 x 10(12) Jones) at its peak emission (~804 nm), which allows an optical signal exchange between two identical diodes. To illustrate the potential of the dual-functional diode, we show that it can be used to create a monolithic pulse sensor and a bidirectional optical communication system.

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  • 12.
    Bao, Chunxiong
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Shenzhen Univ, Peoples R China.
    Yang, Jie
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Southeast Univ, Peoples R China.
    Bai, Sai
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Xu, Weidong
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Yan, Zhibo
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Nanjing Univ, Peoples R China.
    Xu, Qingyu
    Southeast Univ, Peoples R China.
    Liu, Junming
    Nanjing Univ, Peoples R China.
    Zhang, Wenjing
    Shenzhen Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    High Performance and Stable All-Inorganic Metal Halide Perovskite-Based Photodetectors for Optical Communication Applications2018In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 30, no 38, article id 1803422Article in journal (Refereed)
    Abstract [en]

    Photodetectors are critical parts of an optical communication system for achieving efficient photoelectronic conversion of signals, and the response speed directly determines the bandwidth of the whole system. Metal halide perovskites, an emerging class of low-cost solution-processed semiconductors, exhibiting strong optical absorption, low trap states, and high carrier mobility, are widely investigated in photodetection applications. Herein, through optimizing the device engineering and film quality, high-performance photodetectors based on all-inorganic cesium lead halide perovskite (CsPbIxBr3-x), which simultaneously possess high sensitivity and fast response, are demonstrated. The optimized devices processed from CsPbIBr2 perovskite show a practically measured detectable limit of about 21.5 pW cm(-2) and a fast response time of 20 ns, which are both among the highest reported device performance of perovskite-based photodetectors. Moreover, the photodetectors exhibit outstanding long-term environmental stability, with negligible degradation of the photoresponse property after 2000 h under ambient conditions. In addition, the resulting perovskite photodetector is successfully integrated into an optical communication system and its applications as an optical signal receiver on transmitting text and audio signals is demonstrated. The results suggest that all-inorganic metal halide perovskite-based photodetectors have great application potential for optical communication.

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  • 13.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Energetics at Doped Conjugated Polymer/Electrode Interfaces2015In: ADVANCED MATERIALS INTERFACES, ISSN 2196-7350, Vol. 2, no 2Article in journal (Refereed)
    Abstract [en]

    n/a

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  • 14.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Wang, Ergang
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, Sweden.
    Fang, Junfeng
    Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo, PR China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, P. R. China.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and Their Implications of Design Rules2015In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 2, no 12, p. 1-6, article id 1500204Article in journal (Refereed)
    Abstract [en]

    Regular energetics at a conjugated electrolyte/electrode modifier are found and controlled by equilibration of the Fermi level and an additional interface double dipole step induced by ionic functionality. Based on the results, design rules for conjugated electrolyte/electrode modifiers to achieve the smallest charge injection/exaction barrier and break through the current thickness limitation are proposed.

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  • 15.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Xia, Yuxin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Kauffmann, Louis-Dominique
    GenesInk, France.
    Margeat, Olivier
    Aix Marseille University, France.
    Ackermann, Jorg
    Aix Marseille University, France.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Effects of ultraviolet soaking on surface electronic structures of solution processed ZnO nanoparticle films in polymer solar cells2014In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 2, no 41, p. 17676-17682Article in journal (Refereed)
    Abstract [en]

    We systematically show the effect of UV-light soaking on surface electronic structures and chemical states of solution processed ZnO nanoparticle (ZnONP) films in UHV, dry air and UV-ozone. UV exposure in UHV induces a slight decrease in work function and surface-desorption of chemisorbed oxygen, whereas UV exposure in the presence of oxygen causes an increase in work function due to oxygen atom vacancy filling in the ZnO matrix. We demonstrate that UV-light soaking in combination with vacuum or oxygen can tune the work function of the ZnONP films over a range exceeding 1 eV. Based on photovoltaic performance and diode measurements, we conclude that the oxygen atom vacancy filling occurs mainly at the surface of the ZnONP films and that the films consequently retain their n-type behavior despite a significant increase in the measured work function.

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  • 16.
    Beket, Gulzada
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Epishine AB, Linkoping, Sweden.
    Zubayer, Anton
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Zhang, Qilun
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Stahn, Jochen
    Paul Scherer Inst PSI, Switzerland.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Fahlman, Mats
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Osterberg, Thomas
    Epishine AB, Linkoping, Sweden.
    Bergqvist, Jonas
    Epishine AB, Linkoping, Sweden.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Overcoming the voltage losses caused by the acceptor-based interlayer in laminated indoor OPVs2023In: SMARTMAT, ISSN 2766-8525Article in journal (Refereed)
    Abstract [en]

    Harvesting indoor light to power electronic devices for the Internet of Things has become an application scenario for emerging photovoltaics, especially utilizing organic photovoltaics (OPVs). Combined liquid- and solid-state processing, such as printing and lamination used in industry for developing indoor OPVs, also provides a new opportunity to investigate the device structure, which is otherwise hardly possible based on the conventional approach due to solvent orthogonality. This study investigates the impact of fullerene-based acceptor interlayer on the performance of conjugated polymer-fullerene-based laminated OPVs for indoor applications. We observe open-circuit voltage (V-OC) loss across the interface despite this arrangement being presumed to be ideal for optimal device performance. Incorporating insulating organic components such as polyethyleneimine (PEI) or polystyrene (PS) into fullerene interlayers decreases the work function of the cathode, leading to better energy level alignment with the active layer (AL) and reducing the V-OC loss across the interface. Neutron reflectivity studies further uncover two different mechanisms behind the V-OC increase upon the incorporation of these insulating organic components. The self-organized PEI layer could hinder the transfer of holes from the AL to the acceptor interlayer, while the gradient distribution of the PS-incorporated fullerene interlayer eliminates the thermalization losses. This work highlights the importance of structural dynamics near the extraction interfaces in OPVs and provides experimental demonstrations of interface investigation between solution-processed cathodic fullerene layer and bulk heterojunction AL.

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  • 17.
    Cai, Weidong
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Kuang, Chaoyang
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Liu, Tianjun
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Shang, Yuequn
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zhang, Jia
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Qin, Jiajun
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Multicolor light emission in manganese-based metal halide composites2022In: Applied Physics Reviews, E-ISSN 1931-9401, Vol. 9, no 4, article id 041409Article in journal (Refereed)
    Abstract [en]

    Manganese-based organic-inorganic metal halide composites have been considered as promising candidates for lead-free emitters. However, in spite of their excellent luminescence properties in green and red regions, blue emission-a critical component for white light generation-from pristine manganese-based composites is currently missing. In this work, we successfully achieve blue luminescence center in manganese-based composites through selecting specific organic component methylbenzylamine (MBA). Our approach is fundamentally different from green and red emission in manganese-based composites, which result from manganese-halide frameworks. The coexistence of different luminescence centers in our manganese-based composites is confirmed by photoluminescence (PL) and photoluminescence excitation (PLE) results. As a result of different photoluminescence excitation responses of different emission centers, the resulting emission color can be tuned with selecting different excitation wavelengths. Specifically, a white light emission can be obtained with Commission Internationale de leclairage coordinates of (0.33, 0.35) upon the 330 nm excitation. We further demonstrate the promise of our manganese-based composites in the anti-counterfeiting technology and multicolor lighting. Our results provide a novel strategy for full-spectral emission in manganese-based organic-inorganic metal halide composites and lay a solid foundation for a range of new applications. (C) 2022 Author(s).

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  • 18.
    Cai, Weidong
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Qin, Jiajun
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Pang, Tiqiang
    Xidian Univ, Peoples R China.
    Cai, Xinyi
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Jia, Renxu
    Xidian Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Chirality Induced Crystal Structural Difference in Metal Halide Composites2022In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 10, no 16, article id 2102140Article in journal (Refereed)
    Abstract [en]

    Incorporating chiral organic compounds into metal halide frames is a common and useful method to introduce chirality in metal halide composites. The structures of resulting racemic and chiral composites are usually considered to be nearly identical owing to similar chemical bonding. In this work, by incorporating chiral MBABr (bromide methylbenzylamine) into an inorganic frame, a significant crystallization difference between the resulting racemic and chiral metal halide composites is observed, as confirmed by both structural and spectroscopic measurements. In addition, the structural transformation in the chiral composites can also be induced by moisture, ascribed to the asymmetric hydrogen bonding in chiral materials. These results provide new insights for the future synthesis of chiral materials and open up new possibilities to advance the materials functionalities.

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  • 19.
    Cai, Yunhao
    et al.
    Beihang Univ, Peoples R China.
    Zhang, Huotian
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ye, Linglong
    Beihang Univ, Peoples R China.
    Zhang, Rui
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Xu, Jinqiu
    Shanghai Jiao Tong Univ, Peoples R China.
    Zhang, Kangning
    Shandong Univ, Peoples R China.
    Bi, Pengqing
    Shandong Univ, Peoples R China.
    Li, Tengfei
    Peking Univ, Peoples R China.
    Weng, Kangkang
    Beihang Univ, Peoples R China.
    Xu, Ke
    Wuhan Univ Technol, Peoples R China.
    Xia, Jianlong
    Wuhan Univ Technol, Peoples R China.
    Bao, Qinye
    East China Normal Univ, Peoples R China.
    Liu, Feng
    Shanghai Jiao Tong Univ, Peoples R China.
    Hao, Xiaotao
    Shandong Univ, Peoples R China.
    Tan, Songting
    Xiangtan Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zhan, Xiaowei
    Peking Univ, Peoples R China.
    Sun, Yanming
    Beihang Univ, Peoples R China.
    Effect of the Energy Offset on the Charge Dynamics in Nonfullerene Organic Solar Cells2020In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 12, no 39, p. 43984-43991Article in journal (Refereed)
    Abstract [en]

    The energy offset, considered as the driving force for charge transfer between organic molecules, has significant effects on both charge separation and charge recombination in organic solar cells. Herein, we designed material systems with gradually shifting energy offsets, including both positive and negative values. Time-resolved spectroscopy was used to monitor the charge dynamics within the bulk heterojunction. It is striking to find that there is still charge transfer and charge generation when the energy offset reached -0.10 eV (ultraviolet photoelectron spectroscopy data). This work not only indicates the feasibility of the free carrier generation and the following charge separation under the condition of a negative offset but also elucidates the relationship between the charge transfer and the energy offset in the case of polymer chlorination.

  • 20.
    Chai, Gaoda
    et al.
    Hong Kong Univ Sci & Technol, Peoples R China.
    Zhang, Jianquan
    Hong Kong Univ Sci & Technol, Peoples R China.
    Pan, Mingao
    Hong Kong Univ Sci & Technol, Peoples R China.
    Wang, Zhen
    North Carolina State Univ, NC 27695 USA; North Carolina State Univ, NC 27695 USA.
    Yu, Jianwei
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Liang, Jiaen
    Hong Kong Univ Sci & Technol, Peoples R China.
    Yu, Han
    Hong Kong Univ Sci & Technol, Peoples R China.
    Chen, Yuzhong
    Hong Kong Univ Sci & Technol, Peoples R China.
    Shang, Ao
    Hong Kong Univ Sci & Technol, Peoples R China.
    Liu, Xiyuan
    Peking Univ, Peoples R China.
    Bai, Fujin
    Hong Kong Univ Sci & Technol, Peoples R China.
    Ma, Ruijie
    Hong Kong Univ Sci & Technol, Peoples R China.
    Chang, Yuan
    Hong Kong Univ Sci & Technol, Peoples R China.
    Luo, Siwei
    Hong Kong Univ Sci & Technol, Peoples R China.
    Zeng, Anping
    Hong Kong Univ Sci & Technol, Peoples R China.
    Zhou, Hang
    Peking Univ, Peoples R China.
    Chen, Kai
    Xi An Jiao Tong Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Ade, Harald
    North Carolina State Univ, NC 27695 USA; North Carolina State Univ, NC 27695 USA.
    Yan, He
    Hong Kong Univ Sci & Technol, Peoples R China; South China Univ Technol, Peoples R China.
    Deciphering the Role of Chalcogen-Containing Heterocycles in Nonfullerene Acceptors for Organic Solar Cells2020In: ACS Energy Letters, E-ISSN 2380-8195, Vol. 5, no 11, p. 3415-3425Article in journal (Refereed)
    Abstract [en]

    The field of organic solar cells has experienced paradigm-shifting changes in recent years because of the emergence of nonfullerene acceptors (NFAs). It is critically important to gain more insight into the structure-property relationship of the emerging A-DAD-A-type NFAs. In this Letter, a family of NFAs named BPF-4F, BPT-4F, and BPS-4F incorporating various chalcogen-containing heterocycles, i.e., furan, thiophene, and selenophene, respectively, was designed and synthesized. These NFAs exhibited dramatic differences in their photovoltaic performances with device efficiencies of 16.8% achieved by the thiophene-based cells, which was much higher than the furan-based ones (12.6%). In addition, the selenophene-based NFA showed a red-shifted absorption relative to the furan- and thiophene-based ones and obtained a decent efficiency of 16.3% owing to an improved J(SC). The reasons why these NFAs performed differently are systematically studied by comparing their optoelectronic properties and film morphology, which provides new understandings of the molecular design of high-performance NFAs.

  • 21.
    Chen, Desui
    et al.
    Zhejiang Univ, Peoples R China.
    Chen, Dong
    Zhejiang Univ, Peoples R China.
    Dai, Xingliang
    Zhejiang Univ, Peoples R China.
    Zhang, Zhenxing
    Zhejiang Univ, Peoples R China.
    Lin, Jian
    Zhejiang Univ, Peoples R China.
    Deng, Yunzhou
    Zhejiang Univ, Peoples R China.
    Hao, Yanlei
    Zhejiang Univ, Peoples R China.
    Zhang, Ci
    Zhejiang Univ, Peoples R China.
    Zhu, Haiming
    Zhejiang Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Jin, Yizheng
    Zhejiang Univ, Peoples R China.
    Shelf-Stable Quantum-Dot Light-Emitting Diodes with High Operational Performance2020In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 32, article id 2006178Article in journal (Refereed)
    Abstract [en]

    Quantum-dot light-emitting diodes (QLEDs) promise a new generation of high-performance, large-area, and cost-effective electroluminescent devices for both display and solid-state lighting technologies. However, a positive ageing process is generally required to improve device performance for state-of-the-art QLEDs. Here, it is revealed that the in situ reactions induced by organic acids in the commonly used encapsulation acrylic resin lead to positive ageing and, most importantly, the progression of in situ reactions inevitably results in negative ageing, i.e., deterioration of device performance after long-term shelf storage. In-depth mechanism studies focusing on the correlations between the in situ chemical reactions and the shelf-ageing behaviors of QLEDs inspire the design of an electron-transporting bilayer, which delivers both improved electrical conductivity and suppressed interfacial exciton quenching. This material innovation enables red QLEDs exhibiting neglectable changes of external quantum efficiency (>20.0%) and ultralong operational lifetime (T-95: 5500 h at 1000 nits) after storage for 180 days. This work provides design principles for oxide electron-transporting layers to realize shelf-stable and high-operational-performance QLEDs, representing a new starting point for both fundamental studies and practical applications.

  • 22.
    Chen, Haiyang
    et al.
    Soochow Univ, Peoples R China.
    Zhang, Rui
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Chen, Xiaobin
    Soochow Univ, Peoples R China.
    Zeng, Guang
    Soochow Univ, Peoples R China.
    Kobera, Libor
    Czech Acad Sci, Czech Republic.
    Abbrent, Sabina
    Czech Acad Sci, Czech Republic.
    Zhang, Ben
    Soochow Univ, Peoples R China.
    Chen, Weijie
    Soochow Univ, Peoples R China.
    Xu, Guiying
    Soochow Univ, Peoples R China.
    Oh, Jiyeon
    Ulsan Natl Inst Sci & Technol, South Korea.
    Kang, So-Huei
    Ulsan Natl Inst Sci & Technol, South Korea.
    Chen, Shanshan
    Chongqing Univ, Peoples R China.
    Yang, Changduk
    Ulsan Natl Inst Sci & Technol, South Korea.
    Brus, Jiri
    Czech Acad Sci, Czech Republic.
    Hou, Jianhui
    Chinese Acad Sci, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Li, Yaowen
    Soochow Univ, Peoples R China.
    Li, Yongfang
    Soochow Univ, Peoples R China; Chinese Acad Sci, Peoples R China.
    A guest-assisted molecular-organization approach for >17% efficiency organic solar cells using environmentally friendly solvents2021In: Nature Energy, E-ISSN 2058-7546, Vol. 6, no 11, p. 1045-1053Article in journal (Refereed)
    Abstract [en]

    The power conversion efficiencies (PCEs) of laboratory-sized organic solar cells (OSCs), usually processed from low-boiling-point and toxic solvents, have reached high values of over 18%. However, there is usually a notable drop of the PCEs when green solvents are used, limiting practical development of OSCs. Herein, we obtain certificated PCEs over 17% in OSCs processed from a green solvent paraxylene (PX) by a guest-assisted assembly strategy, where a third component (guest) is employed to manipulate the molecular interaction of the binary blend. In addition, the high-boiling-point green solvent PX also enables us to deposit a uniform large-area module (36 cm(2)) with a high efficiency of over 14%. The strong molecular interaction between the host and guest molecules also enhances the operational stability of the devices. Our guest-assisted assembly strategy provides a unique approach to develop large-area and high-efficiency OSCs processed from green solvents, paving the way for industrial development of OSCs. Organic solar cells processed from green solvents are easier to implement in manufacturing yet their efficiency is low. Chen et al. devise a guest molecule to improve the molecular packing, enabling devices with over 17% efficiency.

  • 23.
    Chen, Haoran
    et al.
    Shanghai Jiao Tong Univ, Peoples R China.
    Wang, Yong
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Fan, Yingping
    Shanghai Jiao Tong Univ, Peoples R China.
    Chen, Yuetian
    Shanghai Jiao Tong Univ, Peoples R China.
    Miao, Yanfeng
    Shanghai Jiao Tong Univ, Peoples R China.
    Qin, Zhixiao
    Shanghai Jiao Tong Univ, Peoples R China.
    Wang, Xingtao
    Shanghai Jiao Tong Univ, Peoples R China.
    Liu, Xiaomin
    Shanghai Jiao Tong Univ, Peoples R China.
    Zhu, Kaicheng
    Shanghai Jiao Tong Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zhao, Yixin
    Shanghai Jiao Tong Univ, Peoples R China; Shanghai Inst Pollut Control & Ecol Secur, Peoples R China.
    Decoupling engineering of formamidinium-cesium perovskites for efficient photovoltaics2022In: National Science Review, ISSN 2095-5138, Vol. 9, no 10, article id nwac127Article in journal (Refereed)
    Abstract [en]

    Sequential Cs incorporation strategy is developed to decouple crystallization of FACs perovskite with reduced electron-phonon coupling, resulting in highly stable FACs tri-iodide perovskite photovoltaics with record efficiency. Although pure formamidinium iodide perovskite (FAPbI(3)) possesses an optimal gap for photovoltaics, their poor phase stability limits the long-term operational stability of the devices. A promising approach to enhance their phase stability is to incorporate cesium into FAPbI(3). However, state-of-the-art formamidinium-cesium (FA-Cs) iodide perovskites demonstrate much worse efficiency compared with FAPbI(3), limited by the different crystallization dynamics of formamidinium and cesium, which result in poor composition homogeneity and high trap densities. We develop a novel strategy of crystallization decoupling processes of formamidinium and cesium via a sequential cesium incorporation approach. As such, we obtain highly reproducible, highly efficient and stable solar cells based on FA(1)(-)(x)Cs(x)PbI(3) (x = 0.05-0.16) films with uniform composition distribution in the nanoscale and low defect densities. We also revealed a new stabilization mechanism for Cs doping to stabilize FAPbI(3), i.e. the incorporation of Cs into FAPbI(3) significantly reduces the electron-phonon coupling strength to suppress ionic migration, thereby improving the stability of FA-Cs-based devices.

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  • 24.
    Chen, Hongru
    et al.
    Beijing Univ Chem Technol, Peoples R China.
    Zhang, Zhi-Guo
    Beijing Univ Chem Technol, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Solidification of solvent additive for stable binary polymer solar cells with similar to 19% efficiency2023In: SCIENCE CHINA-MATERIALS, ISSN 2095-8226, Vol. 66, no 6, p. 2523-2524Article in journal (Other academic)
  • 25.
    Chen, K.
    et al.
    Nanjing University, Peoples R China.
    Li, G. L.
    Nanjing University, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Liu, J.
    Nanjing University, Peoples R China.
    Liu, J. M.
    Nanjing University, Peoples R China.
    Zhu, J. S.
    Nanjing University, Peoples R China.
    Conducting grain boundaries in the high-dielectric-constant ceramic CaCu3Ti4O122007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 7, p. 074101-Article in journal (Refereed)
    Abstract [en]

    To clarify the electrical property of grain boundaries, the fine-grained ceramics CaCu3Ti4O12 have been treated with the hydrofluoric acid to remove the parts of grain boundaries. The dielectric response difference between the etched samples and the pristine ones indicates that the ceramic CaCu3Ti4O12 consists of insulating or semiconducting grains with conducting grain boundaries. Therefore, the giant dielectric phenomenon is supposed not to derive from the grain boundary barrier layer capacitance effect. The possible mechanism is discussed. (c) 2007 American Institute of Physics.

  • 26.
    Chen, K.
    et al.
    Nanjing University, Peoples R China.
    Liu, Y. F.
    Nanjing University, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Du, Z. L.
    Nanjing University, Peoples R China.
    Liu, J. M.
    Nanjing University, Peoples R China.
    Ying, X. N.
    Nanjing University, Peoples R China.
    Lu, X. M.
    Nanjing University, Peoples R China.
    Zhu, J. S.
    Nanjing University, Peoples R China.
    Ti deficiency effect on the dielectric response of CaCu3Ti4O12 ceramics2007In: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 141, no 8, p. 440-444Article in journal (Refereed)
    Abstract [en]

    Single phase ceramics CaCu3Ti4.0O12 and CaCu3Ti3.9O12 have been prepared using the traditional solid-state reaction method. Compared with the stoichiometric ceramics CaCu3Ti4.0O12, Ti-deficient ceramics CaCu3Ti3.9O12 have the larger lattice parameter, the higher force constant, and smaller dielectric constant and the lower dissipation factor, although their fundamental characters of dielectric response are similar. Their characteristic relaxation frequencies are not well fitted with the Arrhenius Law but a tentatively supposed relation. With the Cole-Cole Law, the fitted broadened factors of dissipation peaks are 0.5433 and 0.8651 for CaCu3Ti3.9O12 and CaCu3Ti4.0O12, respectively. All facts mentioned above imply that mutually correlated motion of Ti ions or defects may be expected to be responsible for the giant dielectric constant and high dissipation factor of CaCu3T4.0O12. (c) 2006 Elsevier Ltd. All rights reserved.

  • 27.
    Chen, K.
    et al.
    Nanjing University, Peoples R China.
    Yuan, S. K.
    Nanjing University, Peoples R China.
    Li, P. L.
    Nanjing University, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Liu, J.
    Nanjing University, Peoples R China.
    Li, G. L.
    Nanjing University, Peoples R China.
    Zhao, A. G.
    Nanjing University, Peoples R China.
    Lu, X. M.
    Nanjing University, Peoples R China.
    Liu, J. M.
    Nanjing University, Peoples R China.
    Zhu, J. S.
    Nanjing University, Peoples R China.
    High permittivity in zr doped NiO ceramics2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 102, no 3, p. 034103-Article in journal (Refereed)
    Abstract [en]

    We report on measurements of the dielectric permittivity of NiO-based ceramics doped with Zr (ZNO). Samples were prepared by the traditional solid-state reaction method. The concentration of Zr has an effect on the dielectric properties of ZNO ceramics. High permittivity values (similar to 10(4)) were observed which remain almost constant from 200 K to 350 K at low frequencies. The high-dielectric-constant response of the ZNO ceramics is attributed mainly to a grain boundary (internal) barrier layer capacitance. (c) 2007 American Institute of Physics.

  • 28.
    Chen, Kai
    et al.
    Nanjing University, Peoples R China; Nanjing University, Peoples R China; Nanjing University of Science and Technology, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Lin, Weiwei
    Nanjing University, Peoples R China; Nanjing University, Peoples R China.
    Cai, Hongling
    Nanjing University, Peoples R China; Nanjing University, Peoples R China.
    Li, Guolin
    Nanjing University, Peoples R China; Nanjing University, Peoples R China.
    Dong, Xingwei
    Nanjing University, Peoples R China; Nanjing University, Peoples R China.
    Peng, Song
    Nanjing University, Peoples R China; Nanjing University, Peoples R China.
    Wu, Xiaoshan
    Nanjing University, Peoples R China; Nanjing University, Peoples R China.
    Yang, Mao
    Nanjing University, Peoples R China; Nanjing University, Peoples R China.
    Du, Jun
    Nanjing University, Peoples R China; Nanjing University, Peoples R China.
    Lu, Xiaomei
    Nanjing University, Peoples R China; Nanjing University, Peoples R China.
    Liu, Junming
    Nanjing University, Peoples R China; Nanjing University, Peoples R China.
    Zhu, Jinsong
    Nanjing University, Peoples R China; Nanjing University, Peoples R China.
    Room-temperature multiferroic properties in NiBi2O42010In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 89, no 2, article id 27004Article in journal (Refereed)
    Abstract [en]

    Magnetism and ferroelectricity at room temperature are observed in the NiBi2O4 ceramics. Both the time reversal and the inversion symmetry of the structure (space group F-43m) are broken. The saturation magnetization is 0.028 emu/g and the saturation polarization 2P(s) similar to 4.0 mu C/cm(2). NiBi2O4 also shows other room-temperature multiferroic properties, e. g. the piezoelectric coefficient (d(33)), the polarized dielectric character, the magneto-dielectric response and the magnetoelectric effect. Copyright (C) EPLA, 2010

  • 29.
    Chen, Kai
    et al.
    Nanjing University of Science and Technology, Peoples R China; Nanjing University, Peoples R China.
    Guo, Rui
    Nanjing University of Science and Technology, Peoples R China.
    Ma, Chunguang
    Nanjing University of Science and Technology, Peoples R China.
    Dai, Tingyang
    Nanjing University, Peoples R China.
    Ye, Sunjie
    Nanjing University, Peoples R China.
    Lu, Yun
    Nanjing University, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Zhu, Jinsong
    Nanjing University, Peoples R China.
    Jiang, Wei
    Nanjing University of Science and Technology, Peoples R China.
    Self-Assembled Core-Shell Polymer Dielectric Prepared by Solution Casting Process2009In: Integrated Ferroelectrics, ISSN 1058-4587, E-ISSN 1607-8489, Vol. 113, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Giant permittivity at 1 MHz, which slightly changes with temperatures, is observed in a polymer composite. The dielectric spectroscopy demonstrates that the samples are electrically heterogeneous. The microstructure observation and the ingredient analysis evidence they self assemble the conducting cores surrounded by the insulating shells. The giant-dielectric phenomenon is therefore attributed to the percolation effect. The electrically heterogeneous microstructure with effective permittivity values about 10 000 can be fabricated by a simple solution casting process in air. The composite is an attractive option to the currently used printing dielectric and the future flexible electronics.

  • 30.
    Chen, Mengyun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zhang, Tiankai
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Elsukova, Anna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hu, Zhang-Jun
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Zhang, Rui
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Yonghong
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Liu, Xianjie
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Liu, Xiaoke
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Kinetically Controlled Synthesis of Quasi-Square CsPbI<sub>3</sub> Nanoplatelets with Excellent Stability2023In: Small, ISSN 1613-6810, E-ISSN 1613-6829Article in journal (Refereed)
    Abstract [en]

    Nanoplatelets (NPLs) share excellent luminescent properties with their symmetric quantum dots counterparts and entail special characters benefiting from the shape, like the thickness-dependent bandgap and anisotropic luminescence. However, perovskite NPLs, especially those based on iodide, suffer from poor spectral and phase stability. Here, stable CsPbI3 NPLs obtained by accelerating the crystallization process in ambient-condition synthesis are reported. By this kinetic control, the rectangular NPLs into quasi-square NPLs are tuned, where enlarged width endows the NPLs with a lower surface-area-to-volume ratio (S/V ratio), leading to lower surficial energy and thus improved endurance against NPL fusion (cause for spectral shift or phase transformation). The accelerated crystallization, denoting the fast nucleation and short period of growth in this report, is enabled by preparing a precursor with complete transformation of PbI2 into intermediates (PbI3-), through an additional iodide supplier (e.g., zinc iodide). The excellent color stability of the materials remains in the light-emitting diodes under various bias stresses.

  • 31.
    Chen, Shangshang
    et al.
    Hong Kong Univ Sci and Technol, Peoples R China; Hong Kong Univ Sci and Technol, Peoples R China.
    Wang, Yuming
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zhang, Lin
    Xi An Jiao Tong Univ, Peoples R China.
    Zhao, Jingbo
    Hong Kong Univ Sci and Technol, Peoples R China.
    Chen, Yuzhong
    Hong Kong Univ Sci and Technol, Peoples R China.
    Zhu, Danlei
    Chinese Acad Sci, Peoples R China.
    Yao, Huatong
    Hong Kong Univ Sci and Technol, Peoples R China.
    Zhang, Guangye
    Hong Kong Univ Sci and Technol, Peoples R China.
    Ma, Wei
    Xi An Jiao Tong Univ, Peoples R China.
    Friend, Richard H.
    Cavendish Lab, England.
    Chow, Philip C. Y.
    Hong Kong Univ Sci and Technol, Peoples R China; HKUST Shenzhen Res Inst, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Yan, He
    Hong Kong Univ Sci and Technol, Peoples R China; HKUST Shenzhen Res Inst, Peoples R China.
    Efficient Nonfullerene Organic Solar Cells with Small Driving Forces for Both Hole and Electron Transfer2018In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 30, no 45, article id 1804215Article in journal (Refereed)
    Abstract [en]

    State-of-the-art organic solar cells (OSCs) typically suffer from large voltage loss (V-loss) compared to their inorganic and perovskite counterparts. There are some successful attempts to reduce the V-loss by decreasing the energy offsets between the donor and acceptor materials, and the OSC community has demonstrated efficient systems with either small highest occupied molecular orbital (HOMO) offset or negligible lowest unoccupied molecular orbital (LUMO) offset between donors and acceptors. However, efficient OSCs based on a donor/acceptor system with both small HOMO and LUMO offsets have not been demonstrated simultaneously. In this work, an efficient nonfullerene OSC is reported based on a donor polymer named PffBT2T-TT and a small-molecular acceptor (O-IDTBR), which have identical bandgaps and close energy levels. The Fourier-transform photocurrent spectroscopy external quantum efficiency (FTPS-EQE) spectrum of the blend overlaps with those of neat PffBT2T-TT and O-IDTBR, indicating the small driving forces for both hole and electron transfer. Meanwhile, the OSCs exhibit a high electroluminescence quantum efficiency (EQE(EL)) of approximate to 1 x 10(-4), which leads to a significantly minimized nonradiative V-loss of 0.24 V. Despite the small driving forces and a low V-loss, a maximum EQE of 67% and a high power conversion efficiency of 10.4% can still be achieved.

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  • 32.
    Chen, X. Y.
    et al.
    Nanjing University, Peoples R China.
    Yu, T.
    Nanjing University, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Zhang, H. T.
    Nanjing University, Peoples R China.
    Liu, L. F.
    Nanjing University, Peoples R China.
    Wang, Y. M.
    Nanjing University, Peoples R China.
    Li, Z. S.
    Nanjing University, Peoples R China.
    Zou, Z. G.
    Nanjing University, Peoples R China.
    Liu, J.-M.
    Nanjing University, Peoples R China.
    Application of weak ferromagnetic BiFeO3 films as the photoelectrode material under visible-light irradiation2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 2, p. 022114-Article in journal (Refereed)
    Abstract [en]

    BiFeO3 films prepared by pulsed laser deposition on Pt/TiO2/SiO2/Si substrates were studied as photoelectrode for water splitting. Under visible-light irradiation, the photocurrent intensity of the polycrystalline BiFeO3 film was found to double that of the amorphous one in a three-electrode cell. The incident photon to current conversion efficiency for the polycrystalline BiFeO3 electrode was approximately 16% at 350 nm and 7% at 530 nm at 1.5 V (versus saturated calomel electrode). The ferromagnetism of the amorphous BiFeO3 film was an order of magnitude weaker than that of the polycrystalline one, supporting the "size effect" explanation for magnetic origin. (C) 2007 American Institute of Physics.

  • 33.
    Chen, Xian-Kai
    et al.
    Univ Arizona, AZ 85721 USA.
    Qian, Deping
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Yuming
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Kirchartz, Thomas
    Forschungszentrum Julich, Germany; Univ Duisburg Essen, Germany; Univ Duisburg Essen, Germany.
    Tress, Wolfgang
    Zurich Univ Appl Sci, Switzerland.
    Yao, Huifeng
    Chinese Acad Sci, Peoples R China.
    Yuan, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Cent South Univ, Peoples R China.
    Huelsbeck, Markus
    Forschungszentrum Julich, Germany.
    Zhang, Maojie
    Soochow Univ, Peoples R China.
    Zou, Yingping
    Cent South Univ, Peoples R China.
    Sun, Yanming
    Beihang Univ, Peoples R China.
    Li, Yongfang
    Chinese Acad Sci, Peoples R China; Soochow Univ, Peoples R China.
    Hou, Jianhui
    Chinese Acad Sci, Peoples R China.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Coropceanu, Veaceslav
    Univ Arizona, AZ 85721 USA.
    Bredas, Jean-Luc
    Univ Arizona, AZ 85721 USA.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    A unified description of non-radiative voltage losses in organic solar cells2021In: Nature Energy, E-ISSN 2058-7546, Vol. 6, no 8, p. 799-806Article in journal (Refereed)
    Abstract [en]

    Organic solar cells based on non-fullerene acceptors have enabled high efficiencies yet their charge dynamics and its impact on the photovoltaic parameters are not fully understood. Now, Chen et al. provide a general description of non-radiative voltage losses in both fullerene and non-fullerene solar cells. Recent advances in organic solar cells based on non-fullerene acceptors (NFAs) come with reduced non-radiative voltage losses (Delta V-nr). Here we show that, in contrast to the energy-gap-law dependence observed in conventional donor:fullerene blends, the Delta V-nr values in state-of-the-art donor:NFA organic solar cells show no correlation with the energies of charge-transfer electronic states at donor:acceptor interfaces. By combining temperature-dependent electroluminescence experiments and dynamic vibronic simulations, we provide a unified description of Delta V-nr for both fullerene- and NFA-based devices. We highlight the critical role that the thermal population of local exciton states plays in low-Delta V-nr systems. An important finding is that the photoluminescence yield of the pristine materials defines the lower limit of Delta V-nr. We also demonstrate that the reduction in Delta V-nr (for example, &lt;0.2 V) can be obtained without sacrificing charge generation efficiency. Our work suggests designing donor and acceptor materials with high luminescence efficiency and complementary optical absorption bands extending into the near-infrared region.

  • 34.
    Chen, Xuehan
    et al.
    Nanjing Univ Sci & Technol, Peoples R China.
    Huang, Jing
    Nanjing Univ Sci & Technol, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Xu, Bo
    Nanjing Univ Sci & Technol, Peoples R China.
    Perspective Phosphine oxide additives for perovskite diodes and solar cells2023In: Chem, ISSN 2451-9308, E-ISSN 2451-9294, Vol. 9, no 3, p. 562-575Article, review/survey (Refereed)
    Abstract [en]

    Lead halide perovskites have been considered promising semicon-ducting materials for next-generation optoelectronic devices due to their solution processability and excellent optoelectronic proper-ties. Device performance of perovskite light-emitting diodes (PeLEDs) and perovskite solar cells (PSCs) has been rapidly devel-oped during the past decade. Very recently, organic molecules containing phosphine oxide groups have emerged as promising ad-ditives and passivators to improve the device performance and sta-bility of both PeLEDs and PSCs. In this perspective, we summarize recent progress in the development of new phosphine-oxide-based additives for PeLEDs and PSCs. The passivation mechanism, molecule design principle, and structure-property relationship of phosphine oxide molecules for PeLEDs and PSCs are systematically discussed and analyzed. Finally, we provide an outlook on the mo-lecular design of novel phosphine oxide compounds for efficient and stable PeLEDs and PSCs in the future.

  • 35.
    Chen, Zhan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Jinan Univ, Peoples R China.
    Liu, Xiaoke
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Heyong
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Liu, Xianjie
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Hou, Lintao
    Jinan Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Photoluminescence Enhancement for Efficient Mixed-Halide Blue Perovskite Light-Emitting Diodes2023In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071Article in journal (Refereed)
    Abstract [en]

    The development of highly efficient blue perovskite light-emitting diodes (PeLEDs) remains a big challenge, requiring more fundamental investigations. In this work, significant photoluminescence enhancement in mixed halide blue perovskite films is demonstrated by using a molecule, benzylphosphonic acid, which eventually doubles the external quantum efficiency to 6.3% in sky-blue PeLEDs. The photoluminescence enhancement is achieved by forming an oxide-bonded perovskite surface at grain boundaries and suppressing electron-phonon interaction, which enhances the radiative recombination rate and reduces the nonradiative recombination rate, respectively. Moreover, severe thermal quenching is observed in the blue perovskite films, which can be explained by a two-step mechanism involving exciton dissociation and electron-phonon interaction. The results suggest that enhancing the radiative recombination rate and reducing the electron-phonon interaction-induced nonradiative recombination rate are crucial for achieving blue perovskite films with strong emission at or above room temperature.

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  • 36.
    Chen, Zhuoying
    et al.
    University of Cambridge, England.
    Fang, Junfeng
    University of Cambridge, England.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Brenner, Thomas J. K.
    University of Cambridge, England.
    Banger, Kulbinder K.
    University of Cambridge, England.
    Wang, Xingzhu
    University of Cambridge, England.
    Huck, Wilhelm T. S.
    Radboud University of Nijmegen, Netherlands; University of Cambridge, England.
    Sirringhaus, Henning
    University of Cambridge, England.
    Enhanced charge transport by incorporating additional thiophene units in the poly(fluorene-thienyl-benzothiadiazole) polymer2011In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 12, no 3, p. 461-471Article in journal (Refereed)
    Abstract [en]

    We report a comparative study of optical properties, structure and morphology, field-effect transistor (FET) and solar cell performance between poly(4-(3,4-dihexyl-2,2-bithiophen-5-yl)-7-(5-(9,9-dioctyl-9H-fluoren-2-yl)-3,4-dihexyl-2,2-bithiophen-5-yl)benzo[c][1,2,5]-thiadiazole) (F8TTBTT), and its predecessor poly((9,9-dioctylfluorene)-2,7-diyl-alt[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2,2 -diyl) (F8TBT). Compared to F8TBT, F8TTBTT has two more thiophene units incorporated in its monomer structure. Such a modification leads to a reduced optical band gap, improved charge injection and significantly enhanced ambipolar field-effect mobilities reaching 5 x 10 (2) cm(2) V (1) s (1) for holes and 4 x 10 (3) cm(2) V (1) s (1) for electrons. The enhanced carrier mobilities are most likely a result of an increased backbone planarization and interchain interaction. As a consequence of ambipolar transport, light-emission was observed from the transistor channel during operation. The reduced band gap and improved charge transport make F8TTBTT an interesting candidate also for solar cell applications. Unoptimized solar cells based on F8TTBTT: PCBM blends were found to exhibit power conversion efficiency under AM 1.5 illumination of similar to 1.54%. (C) 2011 Published by Elsevier B.V.

  • 37.
    Cheng, Hao-Wen
    et al.
    Univ Calif Los Angeles, CA 90095 USA; Natl Chiao Tung Univ, Taiwan.
    Zhang, Huotian
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Lin, Yu-Che
    Univ Calif Los Angeles, CA 90095 USA; Natl Chiao Tung Univ, Taiwan.
    She, Nian-Zu
    Natl Chiao Tung Univ, Taiwan.
    Wang, Rui
    Univ Calif Los Angeles, CA 90095 USA.
    Chen, Chung-Hao
    Natl Chiao Tung Univ, Taiwan.
    Yuan, Jun
    Univ Calif Los Angeles, CA 90095 USA; Cent S Univ, Peoples R China.
    Tsao, Cheng-Si
    Natl Taiwan Univ, Taiwan; Inst Nucl Energy Res, Taiwan.
    Yabushita, Atsushi
    Natl Chiao Tung Univ, Taiwan.
    Zou, Yingping
    Cent S Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Cheng, Pei
    Univ Calif Los Angeles, CA 90095 USA.
    Wei, Kung-Hwa
    Natl Chiao Tung Univ, Taiwan.
    Yang, Yang
    Univ Calif Los Angeles, CA 90095 USA.
    Realizing Efficient Charge/Energy Transfer and Charge Extraction in Fullerene-Free Organic Photovoltaics via a Versatile Third Component2019In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 19, no 8, p. 5053-5061Article in journal (Refereed)
    Abstract [en]

    Solution-processed organic photovoltaics (OPVs) based on bulk-heterojunctions have gained significant attention to alleviate the increasing demend of fossil fuel in the past two decades. OPVs combined of a wide bandgap polymer donor and a narrow bandgap nonfullerene acceptor show potential to achieve high performance. However, there are still two reasons to limit the OPVs performance. One, although this combination can expand from the ultraviolet to the near-infrared region, the overall external quantum efficiency of the device suffers low values. The other one is the low open-circuit voltage (V-OC) of devices resulting from the relatively downshifted lowest unoccupied molecular orbital (LUMO) of the narrow bandgap. Herein, the approach to select and incorporate a versatile third component into the active layer is reported. A third component with a bandgap larger than that of the acceptor, and absorption spectra and LUMO levels lying within that of the donor and acceptor, is demonstrated to be effective to conquer these issues. As a result, the power conversion efficiencies (PCEs) are enhanced by the elevated short-circuit current and V-OC; the champion PCEs are 11.1% and 13.1% for PTB7-Th:IEICO-4F based and PBDB-T:Y1 based solar cells, respectively.

  • 38.
    Cheng, Li-Peng
    et al.
    Soochow Univ, Peoples R China.
    Huang, Jing-Sheng
    Soochow Univ, Peoples R China.
    Shen, Yang
    Soochow Univ, Peoples R China.
    Li, Guo-Peng
    Hefei Univ Technol HFUT, Peoples R China.
    Liu, Xiaoke
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Li, Wei
    Soochow Univ, Peoples R China.
    Wang, Yu-Han
    Soochow Univ, Peoples R China.
    Li, Yan-Qing
    Soochow Univ, Peoples R China.
    Jiang, Yang
    Hefei Univ Technol HFUT, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Lee, Chun-Sing
    City Univ Hong Kong, Peoples R China.
    Tang, Jian-Xin
    Soochow Univ, Peoples R China.
    Efficient CsPbBr3 Perovskite Light-Emitting Diodes Enabled by Synergetic Morphology Control2019In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 7, no 4, article id 1801534Article in journal (Refereed)
    Abstract [en]

    The development of solution-processed inorganic metal halide perovskite light-emitting diodes (PeLEDs) is currently hindered by low emission efficiency due to morphological defects and severe non-radiative recombination in all-inorganic perovskite emitters. Herein, bright PeLEDs are demonstrated by synergetic morphology control over cesium lead bromide (CsPbBr3) perovskite films with the combination of two additives. The phenethylammonium bromide additive enables the formation of mixed-dimensional CsPbBr3 perovskites featuring the reduced grain size (amp;lt;15 nm) and efficient energy funneling, while the dielectric polyethyleneglycol additive promotes the formation of highly compact and pinhole-free perovskite films with defect passivation at grain boundaries. Consequently, green PeLEDs achieve a current efficiency of 37.14 cd A(-1) and an external quantum efficiency of 13.14% with the maximum brightness up to 45 990 cd m(-2) and high color purity. Furthermore, this method can be effectively extended to realize flexible PeLEDs on plastic substrates with a high efficiency of 31.0 cd A(-1).

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  • 39.
    Clarke, Andrew J.
    et al.
    Swansea Univ, Wales.
    Luke, Joel
    Imperial Coll London, England; Imperial Coll London, England.
    Meitzner, Rico
    Friedrich Schiller Univ Jena, Germany.
    Wu, Jiaying
    Imperial Coll London, England; Imperial Coll London, England.
    Wang, Yuming
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Lee, Harrison K. H.
    Swansea Univ, Wales.
    Speller, Emily M.
    Swansea Univ, Wales.
    Bristow, Helen
    Univ Oxford, England.
    Cha, Hyojung
    Imperial Coll London, England; Imperial Coll London, England.
    Newman, Michael J.
    Swansea Univ, Wales.
    Hooper, Katherine
    Swansea Univ, Wales.
    Evans, Alex
    Cardiff Univ, Wales.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Hoppe, Harald
    Friedrich Schiller Univ Jena, Germany.
    McCulloch, Iain
    Univ Oxford, England; King Abdullah Univ Sci & Technol KAUST, Saudi Arabia.
    Schubert, Ulrich S.
    Friedrich Schiller Univ Jena, Germany; Friedrich Schiller Univ Jena, Germany.
    Watson, Trystan M.
    Swansea Univ, Wales.
    Durrant, James R.
    Swansea Univ, Wales; Imperial Coll London, England; Imperial Coll London, England.
    Tsoi, Wing C.
    Swansea Univ, Wales.
    Kim, Ji-Seon
    Imperial Coll London, England; Imperial Coll London, England.
    Li, Zhe
    Queen Mary Univ London, England.
    Non-fullerene acceptor photostability and its impact on organic solar cell lifetime2021In: Cell Reports Physical Science, E-ISSN 2666-3864, Vol. 2, no 7, article id 100498Article in journal (Refereed)
    Abstract [en]

    The development of non-fullerene acceptors (NFAs) has facilitated the realization of efficient organic solar cells (OSCs) with minimal burn-in losses and excellent long-term stability. However, the role of NFA molecular structures on device stability remains unclear, limiting commercialization of NFA-based OSCs. Herein, the photostability of 10 OSC devices, fabricated with various NFAs (O-IDTBR, EH-IDTBR, ITIC, and ITIC-M) blended with donor polymers (PTB7-Th, PffBT4T-2OD, and PBDB-T), is investigated. O-IDTBR and EH-IDTBR form highly stable devices with all three polymers, whereas ITIC and ITIC-M devices suffer from burn-in losses and long-term degradation. Conformational instability is found to be responsible for the poor photostability of ITIC and ITIC-M, resulting in poor device stability. Twisting and potential breakage of the chemical bond that links the end group to the main backbone of ITIC and ITIC-M molecules causes undesirable conformational changes. Potential strategies to overcome such detrimental photo-induced conformational changes in NFAs are proposed.

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  • 40.
    Cui, Yong
    et al.
    Chinese Acad Sci, Peoples R China.
    Hong, Ling
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Zhang, Tao
    Chinese Acad Sci, Peoples R China.
    Meng, Haifeng
    Natl Inst Metrol, Peoples R China.
    Yan, He
    Hong Kong Univ Sci & Technol, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Hou, Jianhui
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Accurate photovoltaic measurement of organic cells for indoor applications2021In: Joule, E-ISSN 2542-4351, Vol. 5, no 5, p. 1016-1023Article in journal (Other academic)
    Abstract [en]

    Photovoltaic (PV) cells offer a convenient energy source to drive micropower electronic devices for indoor applications. However, it is challenging to measure the power conversion efficiency (PCE) of PV cells under indoor lighting and the PV community lacks a feasible and accurate measurement protocol. Here, we start with the fundamental parameters which determine the PCE, and carefully design a series of experiments to examine the origins which might cause measurement errors for organic PV measurements under indoor lighting. We demonstrate the critical importance of: 1, temporal stability and spatial homogeneity of the light sources, 2, calibration of the spectral irradiance and illuminations of the light sources, 3, the area of the cells (1 cm2 or large cells are preferred), 4, the aperture of the mask (an aperture slightly smaller than the cell area is preferred), and 5, stray lights from the measurement environment. Based on these careful investigations, we suggest a feasible measurement method, by which accurate measurement of the indoor PV efficiency is made possible. Our study will promote the healthy development of indoor PV technology for practical applications.

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  • 41.
    Cui, Yong
    et al.
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Wang, Yuming
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Bergqvist, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Yao, Huifeng
    Chinese Acad Sci, Peoples R China.
    Xu, Ye
    Univ Chinese Acad Sci, Peoples R China.
    Gao, Bowei
    Univ Chinese Acad Sci, Peoples R China.
    Yang, Chenyi
    Univ Sci and Technol Beijing, Peoples R China.
    Zhang, Shaoqing
    Univ Sci and Technol Beijing, Peoples R China.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Hou, Jianhui
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China; Univ Sci and Technol Beijing, Peoples R China.
    Wide-gap non-fullerene acceptor enabling high-performance organic photovoltaic cells for indoor applications2019In: NATURE ENERGY, ISSN 2058-7546, Vol. 4, no 9, p. 768-775Article in journal (Refereed)
    Abstract [en]

    Organic photovoltaic cells are potential candidates to drive low power consumption off-grid electronics for indoor applications. However, their power conversion efficiency is still limited by relatively large losses in the open-circuit voltage and a non-optimal absorption spectrum for indoor illumination. Here, we carefully designed a non-fullerene acceptor named IO-4CI and blend it with a polymer donor named PBDB-TF to obtain a photoactive layer whose absorption spectrum matches that of indoor light sources. The photovoltaic characterizations reveal a low energy loss below 0.60 eV. As a result, the organic photovoltaic cell (1 cm(2)) shows a power conversion efficiency of 26.1% with an open-circuit voltage of 1.10 V under a light-emitting diode illumination of 1,000 lux (2,700 K). We also fabricated a large-area cell (4 cm(2)) through the blade-coating method. Our cell shows an excellent stability, maintaining its initial photovoltaic performance under continuous illumination of the indoor light source for 1,000 hours.

  • 42.
    Cui, Yong
    et al.
    Chinese Academic Science, Peoples R China; University of Chinese Academic Science, Peoples R China.
    Yang, Chenyi
    Chinese Academic Science, Peoples R China; University of Science and Technology Beijing, Peoples R China.
    Yao, Huifeng
    Chinese Academic Science, Peoples R China.
    Zhu, Jie
    Chinese Academic Science, Peoples R China; Ocean University of China, Peoples R China.
    Wang, Yuming
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Jia, Guoxiao
    Chinese Academic Science, Peoples R China; University of Science and Technology Beijing, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Hou, Jianhui
    Chinese Academic Science, Peoples R China; University of Chinese Academic Science, Peoples R China.
    Efficient Semitransparent Organic Solar Cells with Tunable Color enabled by an Ultralow-Bandgap Nonfullerene Acceptor2017In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 29, no 43, article id 1703080Article in journal (Refereed)
    Abstract [en]

    Semitransparent organic solar cells (OSCs) show attractive potential in power-generating windows. However, the development of semitransparent OSCs is lagging behind opaque OSCs. Here, an ultralow-bandgap non-fullerene acceptor, "IEICO-4Cl", is designed and synthesized, whose absorption spectrum is mainly located in the near-infrared region. When IEICO-4Cl is blended with different polymer donors (J52, PBDB-T, and PTB7-Th), the colors of the blend films can be tuned from purple to blue to cyan, respectively. Traditional OSCs with a nontransparent Al electrode fabricated by J52: IEICO-4Cl, PBDB-T: IEICO-4Cl, and PTB7-Th: IEICO-4Cl yield power conversion efficiencies (PCE) of 9.65 +/- 0.33%, 9.43 +/- 0.13%, and 10.0 +/- 0.2%, respectively. By using 15 nm Au as the electrode, semitransparent OSCs based on these three blends also show PCEs of 6.37%, 6.24%, and 6.97% with high average visible transmittance (AVT) of 35.1%, 35.7%, and 33.5%, respectively. Furthermore, via changing the thickness of Au in the OSCs, the relationship between the transmittance and efficiency is studied in detail, and an impressive PCE of 8.38% with an AVT of 25.7% is obtained, which is an outstanding value in the semitransparent OSCs.

  • 43.
    Cui, Yong
    et al.
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Yao, Huifeng
    Chinese Acad Sci, Peoples R China.
    Zhang, Jianqi
    Natl Ctr Nanosci and Technol, Peoples R China.
    Xian, Kaihu
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Zhang, Tao
    Chinese Acad Sci, Peoples R China.
    Hong, Ling
    Univ Chinese Acad Sci, Peoples R China.
    Wang, Yuming
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Chinese Acad Sci, Peoples R China.
    Xu, Ye
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Ma, Kangqiao
    Chinese Acad Sci, Peoples R China.
    An, Cunbin
    Chinese Acad Sci, Peoples R China.
    He, Chang
    Chinese Acad Sci, Peoples R China.
    Wei, Zhixiang
    Univ Chinese Acad Sci, Peoples R China; Natl Ctr Nanosci and Technol, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Hou, Jianhui
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Single-Junction Organic Photovoltaic Cells with Approaching 18% Efficiency2020In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 32, no 19, article id 1908205Article in journal (Refereed)
    Abstract [en]

    Optimizing the molecular structures of organic photovoltaic (OPV) materials is one of the most effective methods to boost power conversion efficiencies (PCEs). For an excellent molecular system with a certain conjugated skeleton, fine tuning the alky chains is of considerable significance to fully explore its photovoltaic potential. In this work, the optimization of alkyl chains is performed on a chlorinated nonfullerene acceptor (NFA) named BTP-4Cl-BO (a Y6 derivative) and very impressive photovoltaic parameters in OPV cells are obtained. To get more ordered intermolecular packing, the n-undecyl is shortened at the edge of BTP-eC11 to n-nonyl and n-heptyl. As a result, the NFAs of BTP-eC9 and BTP-eC7 are synthesized. The BTP-eC7 shows relatively poor solubility and thus limits its application in device fabrication. Fortunately, the BTP-eC9 possesses good solubility and, at the same time, enhanced electron transport property than BTP-eC11. Significantly, due to the simultaneously enhanced short-circuit current density and fill factor, the BTP-eC9-based single-junction OPV cells record a maximum PCE of 17.8% and get a certified value of 17.3%. These results demonstrate that minimizing the alkyl chains to get suitable solubility and enhanced intermolecular packing has a great potential in further improving its photovoltaic performance.

  • 44.
    Cui, Yong
    et al.
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Yao, Huifeng
    Chinese Acad Sci, Peoples R China.
    Zhang, Jianqi
    Natl Ctr Nanosci and Technol, Peoples R China.
    Zhang, Tao
    Chinese Acad Sci, Peoples R China.
    Wang, Yuming
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Hong, Ling
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Xian, Kaihu
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Xu, Bowei
    Chinese Acad Sci, Peoples R China.
    Zhang, Shaoqing
    Chinese Acad Sci, Peoples R China; Univ Sci and Technol Beijing, Peoples R China.
    Peng, Jing
    Organtec Ltd, Peoples R China.
    Wei, Zhixiang
    Natl Ctr Nanosci and Technol, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Hou, Jianhui
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Over 16% efficiency organic photovoltaic cells enabled by a chlorinated acceptor with increased open-circuit voltages2019In: Nature Communications, E-ISSN 2041-1723, Vol. 10, article id 2515Article in journal (Refereed)
    Abstract [en]

    Broadening the optical absorption of organic photovoltaic (OPV) materials by enhancing the intramolecular push-pull effect is a general and effective method to improve the power conversion efficiencies of OPV cells. However, in terms of the electron acceptors, the most common molecular design strategy of halogenation usually results in down-shifted molecular energy levels, thereby leading to decreased open-circuit voltages in the devices. Herein, we report a chlorinated non-fullerene acceptor, which exhibits an extended optical absorption and meanwhile displays a higher voltage than its fluorinated counterpart in the devices. This unexpected phenomenon can be ascribed to the reduced non-radiative energy loss (0.206 eV). Due to the simultaneously improved short-circuit current density and open-circuit voltage, a high efficiency of 16.5% is achieved. This study demonstrates that finely tuning the OPV materials to reduce the bandgap-voltage offset has great potential for boosting the efficiency.

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  • 45.
    Dai, Tingyang
    et al.
    Nanjing University, Peoples R China.
    Chen, Kai
    Nanjing University of Science and Technology, Peoples R China.
    Qing, Xutang
    Nanjing University, Peoples R China.
    Lu, Yun
    Nanjing University, Peoples R China.
    Zhu, Jinsong
    Nanjing University, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Sequential Polymer Precipitation of Core-Shell Microstructured Composites with Giant Permittivity2010In: Macromolecular rapid communications, ISSN 1022-1336, E-ISSN 1521-3927, Vol. 31, no 5, p. 484-489Article in journal (Refereed)
    Abstract [en]

    Polymeric core shell microstructures have been constructed through a new method, namely sequential precipitation, which is intrinsically a self-assembly and phase separation process. High-quality poly(vinyldene fluoride)-polycarbonate-lithium perchlorate composite films with spherical core shell microstructures have been prepared and determined to consist of conducting cores and insulating shells. Because of the percolation effect, the resulting materials present a dielectric constant as high as 10(4)-10(7) at the threshold.

  • 46.
    Deng, Lin-Long
    et al.
    Xiamen Univ, Peoples R China.
    Xie, Su-Yuan
    Xiamen Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Fullerene-Based Materials for Photovoltaic Applications: Toward Efficient, Hysteresis-Free, and Stable Perovskite Solar Cells2018In: Advanced Electronic Materials, E-ISSN 2199-160X, Vol. 4, no 10, article id 1700435Article in journal (Refereed)
    Abstract [en]

    Perovskite solar cells are promising candidates for next-generation photovoltaics. Fullerenes and their derivatives can act as efficient electron transport layers, interfacial modification layers, and trap state passivators in perovskite solar cells, all of which play an important role in increasing efficiency, reducing current hysteresis, and enhancing device stability. Herein, recent progress in the use of fullerenes and their derivatives in perovskite solar cells is reviewed, with a particular emphasis on fullerene chemical structures that affect device performance. Potential fullerene candidates that could further improve device performance and stability are also discussed.

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  • 47.
    Dong, S.
    et al.
    Nanjing University, MA 02460 USA.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Wang, Z. Q.
    Nanjing University, MA 02460 USA.
    Liu, J. -M.
    Nanjing University, MA 02460 USA.
    Ren, Z. F.
    Nanjing University, MA 02460 USA.
    Surface phase separation in nanosized charge-ordered manganites2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 8, p. 082508-Article in journal (Refereed)
    Abstract [en]

    Recent experiments showed that the robust charge ordering in manganites can be weakened by reducing the grain size down to nanoscale. Weak ferromagnetism was evidenced in both nanoparticles and nanowires of charge-ordered manganites. To explain these observations, a phenomenological model based on surface phase separation is proposed. The relaxation of superexchange interaction on the surface layer allows formation of a ferromagnetic shell, whose thickness increases with decreasing grain size. Possible exchange bias and softening of the ferromagnetic transition in nanosized charge-ordered manganites are predicted. (c) 2007 American Institute of Physics.

  • 48.
    Dávid, Anna
    et al.
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Morat, Julia
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Chen, Mengyun
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Fahlman, Mats
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Liu, Xianjie
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Mapping Uncharted Lead-Free Halide Perovskites and Related Low-Dimensional Structures2024In: Materials, E-ISSN 1996-1944, Vol. 17, no 2, article id 491Article, review/survey (Refereed)
    Abstract [en]

    Research on perovskites has grown exponentially in the past decade due to the potential of methyl ammonium lead iodide in photovoltaics. Although these devices have achieved remarkable and competitive power conversion efficiency, concerns have been raised regarding the toxicity of lead and its impact on scaling up the technology. Eliminating lead while conserving the performance of photovoltaic devices is a great challenge. To achieve this goal, the research has been expanded to thousands of compounds with similar or loosely related crystal structures and compositions. Some materials are "re-discovered", and some are yet unexplored, but predictions suggest that their potential applications may go beyond photovoltaics, for example, spintronics, photodetection, photocatalysis, and many other areas. This short review aims to present the classification, some current mapping strategies, and advances of lead-free halide double perovskites, their derivatives, lead-free perovskitoid, and low-dimensional related crystals.

  • 49.
    Fan, Baobing
    et al.
    City Univ Hong Kong, Peoples R China; City Univ Hong Kong, Peoples R China.
    Gao, Wei
    City Univ Hong Kong, Peoples R China; City Univ Hong Kong, Peoples R China.
    Zhang, Rui
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Kaminsky, Werner
    Univ Washington, WA 98195 USA.
    Lin, Francis R.
    City Univ Hong Kong, Peoples R China; City Univ Hong Kong, Peoples R China.
    Xia, Xinxin
    Chinese Univ Hong Kong, Peoples R China.
    Fan, Qunping
    Xi An Jiao Tong Univ, Peoples R China.
    Li, Yanxun
    City Univ Hong Kong, Peoples R China; City Univ Hong Kong, Peoples R China.
    An, Yidan
    City Univ Hong Kong, Peoples R China; City Univ Hong Kong, Peoples R China.
    Wu, Yue
    City Univ Hong Kong, Peoples R China; City Univ Hong Kong, Peoples R China.
    Liu, Ming
    City Univ Hong Kong, Peoples R China; City Univ Hong Kong, Peoples R China.
    Lu, Xinhui
    Chinese Univ Hong Kong, Peoples R China.
    Li, Wen Jung
    City Univ Hong Kong, Peoples R China.
    Yip, Hin-Lap
    City Univ Hong Kong, Peoples R China; City Univ Hong Kong, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Jen, Alex K. -Y.
    City Univ Hong Kong, Peoples R China; City Univ Hong Kong, Peoples R China; City Univ Hong Kong, Peoples R China; Univ Washington, WA 98195 USA.
    Correlation of Local Isomerization Induced Lateral and Terminal Torsions with Performance and Stability of Organic Photovoltaics2023In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 145, no 10, p. 5909-5919Article in journal (Refereed)
    Abstract [en]

    Organic photovoltaics (OPVs) have achieved great progress in recent years due to delicately designed non-fullerene acceptors (NFAs). Compared with tailoring of the aromatic heterocycles on the NFA backbone, the incorporation of conjugated side-groups is a cost-effective way to improve the photoelectrical properties of NFAs. However, the modifications of side-groups also need to consider their effects on device stability since the molecular planarity changes induced by side-groups are related to the NFA aggregation and the evolution of the blend morphology under stresses. Herein, a new class of NFAs with localisomerized conjugated side-groups are developed and the impact of local isomerization on their geometries and device performance/stability are systematically investigated. The device based on one of the isomers with balanced side- and terminal-group torsion angles can deliver an impressive power conversion efficiency (PCE) of 18.5%, with a low energy loss (0.528 V) and an excellent photo- and thermal stability. A similar approach can also be applied to another polymer donor to achieve an even higher PCE of 18.8%, which is among the highest efficiencies obtained for binary OPVs. This work demonstrates the effectiveness of applying local isomerization to fine-tune the side-group steric effect and non-covalent interactions between side-group and backbone, therefore improving both photovoltaic performance and stability of fused ring NFA-based OPVs.

  • 50.
    Fan, Baobing
    et al.
    City Univ Hong Kong, Peoples R China.
    Gao, Wei
    City Univ Hong Kong, Peoples R China.
    Zhang, Rui
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Kaminsky, Werner
    Univ Washington, WA 98195 USA.
    Tang, Lingxiao
    Xi An Jiao Tong Univ, Peoples R China.
    Lin, Francis R.
    City Univ Hong Kong, Peoples R China.
    Wang, Yiwen
    City Univ Hong Kong, Peoples R China.
    Fan, Qunping
    Xi An Jiao Tong Univ, Peoples R China.
    Ma, Wei
    Xi An Jiao Tong Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Jen, Alex K. -Y.
    City Univ Hong Kong, Peoples R China; Univ Washington, WA 98195 USA.
    Correlation of Broad Absorption Band with Small Singlet-Triplet Energy Gap in Organic Photovoltaics2023In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773Article in journal (Refereed)
    Abstract [en]

    Organic photovoltaics (OPV) are one of the most effective ways to harvest renewable solar energy, with the power conversion efficiency (PCE) of the devices soaring above 19% when processed with halogenated solvents. The superior photocurrent of OPV over other emerging photovoltaics offers more opportunities to further improve the efficiency. Tailoring the absorption band of photoactive materials is an effective way to further enhance OPV photocurrent. However, the field has mostly been focusing on improving the near-infrared region photo-response, with the absorption shoulders in short-wavelength region (SWR) usually being neglected. Herein, by developing a series of non-fullerene acceptors (NFAs) with varied side-group conjugations, we observe an enhanced SWR absorption band with increased side-group conjugation length. The underpinning factors of how molecular structures and geometries improve SWR absorption are clearly elucidated through theoretical modelling and crystallography. Moreover, a clear relationship between the enhanced SWR absorption and reduced singlet-triplet energy gap is established, both of which are favorable for the OPV performance and can be tailored by rational structure design of NFAs. Finally, the rationally designed NFA, BO-TTBr, affords a decent PCE of 18.5% when processed with a non-halogenated green solvent.

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