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  • 1.
    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, 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

  • 2.
    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.

  • 3.
    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, ISSN 2046-2069, 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.

  • 4.
    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, 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.

  • 5.
    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.

  • 6.
    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.

  • 7.
    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.

  • 8.
    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.

  • 9.
    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

  • 10.
    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, Slawomirslama19
    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.

  • 11.
    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.

  • 12.
    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.

  • 13.
    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.

  • 14.
    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.

  • 15.
    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

  • 16.
    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.

  • 17.
    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.

  • 18.
    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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    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).

  • 22.
    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.

  • 23.
    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, ISSN 2041-1723, 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.

  • 24.
    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.

  • 25.
    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, 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.

  • 26.
    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.

  • 27.
    Fang, Junfeng
    et al.
    University of Cambridge, England.
    Wallikewitz, Bodo H.
    University of Cambridge, England.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Tu, Guoli
    University of Cambridge, England; Huazhong University of Science and Technology, Peoples R China.
    Mueller, Christian
    University of Cambridge, England.
    Pace, Giuseppina
    University of Cambridge, England.
    Friend, Richard H.
    University of Cambridge, England.
    Huck, Wilhelm T. S.
    University of Cambridge, England; Radboud University of Nijmegen, Netherlands.
    Conjugated Zwitterionic Polyelectrolyte as the Charge Injection Layer for High-Performance Polymer Light-Emitting Diodes2011In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 133, no 4, p. 683-685Article in journal (Refereed)
    Abstract [en]

    A new zwitterionic conjugated polyelectrolyte without free counterions has been used as an electron injection material in polymer light-emitting diodes. Both the efficiency and maximum brightness were considerably improved in comparison with standard Ca cathode devices. The devices showed very fast response times, indicating that the improved performance is, in addition to hole blocking, due to dipoles at the cathode interface, which facilitate electron injection.

  • 28.
    Fu, Huiting
    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.
    Meng, Dong
    Chinese Acad Sci, Peoples R China.
    Ma, Zetong
    Chinese Acad Sci, Peoples R China; Univ Chinese Acad Sci, Peoples R China.
    Li, Yan
    Chinese Acad Sci, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Wang, Zhaohui
    Chinese Acad Sci, Peoples R China.
    Sun, Yanming
    Beihang Univ, Peoples R China.
    Suppression of Recombination Energy Losses by Decreasing the Energetic Offsets in Perylene Diimide-Based Nonfullerene Organic Solar Cells2018In: ACS ENERGY LETTERS, ISSN 2380-8195, Vol. 3, no 11, p. 2729-2735Article in journal (Refereed)
    Abstract [en]

    In this work, a range of nonfullerene organic solar cells comprising two perylene diimide (PDI)-based small molecule acceptors in combination with four representative polymer donors have been investigated and compared. In addition to significant differences in the power conversion efficiency, the energy losses of photovoltaic devices vary widely for these two PDI-based acceptors when paired with different donors. The sensitive Fourier-transform photocurrent spectroscopy (FTPS) and electroluminescence (EL) measurements have been performed to quantify their respective energetic offsets (Delta(Eoffiet)) and energy losses, with the aim of understanding the distinct energy losses in the studied organic blends. By comparing these results, we find that with decreasing Delta(Eoffset), recombination loss due to the charge-transfer state absorption A both nonradiative recombination loss and radiative are suppressed; as a result, the total energy loss is decreased. These observations offer a deep understanding of how the energetic offset affects the energy losses from the viewpoint of the Shockey-Queisser limit.

  • 29.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    A New Acceptor for Highly Efficient Organic Solar Cells2019In: JOULE, ISSN 2542-4351, Vol. 3, no 4, p. 908-909Article in journal (Other academic)
    Abstract [en]

    Research into organic solar cells has gone from pure scientific curiosity to a topic of commercial relevance in the past few years, as a result of rapid development of non-fullerene acceptors. This transition is mainly driven by the development of new materials. Recently in Joule, Zou and co-workers developed a new acceptor material and reached a record efficiency for single-junction organic solar cells.

  • 30.
    Gao, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Cai, C.
    Nanjing University, Peoples R China.
    Wang, Y.
    Nanjing University, Peoples R China.
    Dong, S.
    Nanjing University, Peoples R China.
    Qiu, X. Y.
    Nanjing University, Peoples R China.
    Yuan, G. L.
    Nanjing University, Peoples R China.
    Liu, Z. G.
    Nanjing University, Peoples R China.
    Liu, J. -M.
    Nanjing University, Peoples R China.
    Preparation of la-doped BiFeO3 thin films with Fe2+ ions on Si substrates2006In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 99, no 9, p. 094105-Article in journal (Refereed)
    Abstract [en]

    La-doped BiFeO3 thin films with Fe2+ ions have been prepared on Pt/TiO2/SiO2/Si substrates by pulsed laser deposition in order to enhance the ferroelectric and magnetic properties. The targets for the film deposition were synthesized using a rapid liquid phase sintering technique to ensure the low leakage. The dielectric properties at room temperature and above were investigated. It was observed that the La doping greatly enhances the ferroelectric polarization at room temperature by modifying the film structure from rhombohedral to monoclinic. The saturation magnetization was enhanced about two times due to the Fe2+ ions in the thin films. (C) 2006 American Institute of Physics.

  • 31.
    Gao, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Chen, Xinyi
    Nanjing University, China.
    Yin, Kuibo
    Nanjing University, China.
    Dong, Shuai
    Nanjing University, China.
    Ren, Zhifeng
    Boston College, USA.
    Yuan, Fang
    Nanjing University, China.
    Yu, Tao
    Nanjing University, China.
    Zou, Zhigang
    Nanjing University, China.
    Liu, Jun-Ming
    Nanjing University, China.
    Visible-light photocatalytic properties of weak magnetic BiFeO3 nanoparticles2007In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 19, no 19, p. 2889-2892Article in journal (Refereed)
    Abstract [en]

    Polycrystalline BiFeO3 nanoparticles (size 80-120 nm) are prepared by a simple sol-gel technique. Such nanoparticles are very efficient for photocatalytic decomposition of organic contaminants under irradiation from ultraviolet to visible frequencies. The BiFeO3 nanoparticles also demonstrate weak ferromagnetism of about 0.06 mu(B)/Fe at room temperature, in good agreement with theoretical calculations.

  • 32.
    Gao, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Himmelberger, Scott
    Stanford University, CA 94305 USA.
    Andersson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Hanifi, David
    Stanford University, CA 94305 USA.
    Xia, Yuxin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zhang, Shaoqing
    Chinese Academic Science, Peoples R China.
    Wang, Jianpu
    Nanjing Technical University, Peoples R China; Nanjing Technical University, Peoples R China.
    Hou, Jianhui
    Chinese Academic Science, Peoples R China.
    Salleo, Alberto
    Stanford University, CA 94305 USA.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    The Effect of Processing Additives on Energetic Disorder in Highly Efficient Organic Photovoltaics: A Case Study on PBDTTT-C-T:PC71BM2015In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 27, no 26, p. 3868-3873Article in journal (Refereed)
    Abstract [en]

    Energetic disorder, an important parameter affecting the performance of organic photovoltaics, is significantly decreased upon the addition of processing additives in a highly efficient benzodithiophene-based copolymer blend (PBDTTT-C-T:PC71BM). Wide-angle and small-angle X-ray scattering measurements suggest that the origin of this reduced energetic disorder is due to increased aggregation and a larger average fullerene domain size together with purer phases.

  • 33.
    Gao, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Charge generation in polymer-fullerene bulk-heterojunction solar cells2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 38, p. 20291-20304Article in journal (Refereed)
    Abstract [en]

    Charge generation in organic solar cells is a fundamental yet heavily debated issue. This article gives a balanced review of different mechanisms proposed to explain efficient charge generation in polymer-fullerene bulk-heterojunction solar cells. We discuss the effect of charge-transfer states, excess energy, external electric field, temperature, disorder of the materials, and delocalisation of the charge carriers on charge generation. Although a general consensus has not been reached yet, recent findings, based on both steady-state and transient measurements, have significantly advanced our understanding of this process.

  • 34.
    Gao, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Koster, L. Jan Anton
    Univ Groningen, Netherlands.
    Nguyen, Thuc-Quyen
    Univ Calif Santa Barbara, CA 93106 USA.
    Stingelin, Natalie
    Georgia Tech, GA 30313 USA.
    Organic Photovoltaics2018In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 8, no 28, article id 1802706Article in journal (Other academic)
    Abstract [en]

    n/a

  • 35.
    Gao, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Li, P. L.
    Nanjing University, China.
    Weng, Y. Y.
    Nanjing University, China.
    Dong, S.
    Nanjing University, China.
    Wang, L. F.
    Nanjing University, China.
    Lv, L. Y.
    Nanjing University, China.
    Wang, K. F.
    Nanjing University, China.
    Liu, J.-M.
    Nanjing University, China.
    Ren, Z. F.
    Nanjing University, MA 02467 USA.
    Charge order suppression and weak ferromagnetism in La1/3Sr2/3FeO3 nanoparticles2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 7, p. 072504-Article in journal (Refereed)
    Abstract [en]

    Perovskite-type polycrystalline La1/3Sr2/3FeO3 particles with different sizes (80-2000 nm) were prepared using a simple sol-gel technique. In samples of nanoparticles with a diameter of less than 300 nm, weak ferromagnetism was observed at room temperature, which was attributed to the lattice distortion. The magnetic and specific heat measurements suggest that the charge ordering state was largely suppressed due to the lowering of the particle size, but the charge ordering temperature remained unaffected. (C) 2007 American Institute of Physics.

  • 36.
    Gao, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Li, Zhe
    University of Cambridge, England.
    Wang, Jianpu
    University of Cambridge, England.
    Rao, Akshay
    University of Cambridge, England.
    Howard, Ian A.
    University of Cambridge, England.
    Abrusci, Agnese
    University of Cambridge, England.
    Massip, Sylvain
    University of Cambridge, England.
    McNeill, Christopher R.
    University of Cambridge, England.
    Greenham, Neil C.
    University of Cambridge, England.
    Trap-Induced Losses in Hybrid Photovoltaics2014In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, no 4, p. 3213-3221Article in journal (Refereed)
    Abstract [en]

    We investigate the loss mechanisms in hybrid photovoltaics based on blends of poly(3-hexylthiophene) with CdSe nanocrystals of various sizes. By combining the spectroscopic and electrical measurements on working devices as well as films, we identify that high trap-mediated recombination is responsible for the loss of photogenerated charge carriers in devices with small nanocrystals. In addition, we demonstrate that the reduced open-circuit voltage for devices with small nanocrystals is also caused by the traps.

  • 37.
    Gao, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Qiu, X. Y.
    Nanjing University, Peoples R China.
    Yuan, Y.
    Nanjing University, Peoples R China.
    Xu, B.
    Nanjing University, Peoples R China.
    Wen, Y. Y.
    Nanjing University, Peoples R China.
    Yuan, F.
    Nanjing University, Peoples R China.
    Lv, L. Y.
    Nanjing University, Peoples R China.
    Liu, J.-M.
    Nanjing University, Peoples R China.
    Effects of substrate temperature on Bi0.8La0.2FeO3 thin films prepared by pulsed laser deposition2007In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 515, no 13, p. 5366-5373Article in journal (Refereed)
    Abstract [en]

    Bi0.8La0.2FeO3 thin films on Pt/TiO2/SiO2/Si substrates at various substrate temperatures from 500 degrees C to 750 degrees C are prepared by pulsed laser deposition, and their microstructures and ferroelectric/magnetic properties are carefully investigated using various techniques. It is observed that the crystallographic orientation and Fe-ion valence state depend significantly on the substrate temperature, which consequently influences considerably on the ferroelectric and magnetic properties of the thin films. A considerable improvement of the ferroelectric and magnetic properties of the thin films can be achieved by optimizing the substrate temperature for deposition. (C) 2007 Elsevier B.V. All rights reserved.

  • 38.
    Gao, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Ren, Shenqiang
    University of Kansas, USA.
    Wang, Jianpu
    University of Cambridge, England.
    The renaissance of hybrid solar cells: progresses, challenges, and perspectives2013In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 6, no 7, p. 2020-2040Article, review/survey (Refereed)
    Abstract [en]

    Solution-processed hybrid solar cells, a blend of conjugated polymers and semiconducting nanocrystals, are a promising candidate for next-generation energy-conversion devices. The renaissance of this field in recent years has yielded a much deeper understanding of optoelectronic interactions in organic–inorganic hybrid systems. In this article, we review the state-of-the-art progress in hybrid bulk heterojunction solar cells, covering new materials design, interfacial interaction, and processing control. Furthermore, critical challenges that determine photovoltaic performance and prospects for future directions are discussed.

  • 39.
    Gao, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology. University of Cambridge, England.
    Tress, Wolfgang
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Wang, Jianpu
    University of Cambridge, England; Nanjing Technical University, Peoples R China; Nanjing Technical University, Peoples R China.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Temperature Dependence of Charge Carrier Generation in Organic Photovoltaics2015In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 114, no 12, p. 128701-Article in journal (Refereed)
    Abstract [en]

    The charge generation mechanism in organic photovoltaics is a fundamental yet heavily debated issue. All the generated charges recombine at the open-circuit voltage (VOC), so that investigation of recombined charges at VOC provides a unique approach to understanding charge generation. At low temperatures, we observe a decrease of VOC, which is attributed to reduced charge separation. Comparison between benchmark polymer: fullerene and polymer: polymer blends highlights the critical role of charge delocalization in charge separation and emphasizes the importance of entropy in charge generation.

  • 40.
    Gao, Feng
    et al.
    University of Cambridge, England.
    Wang, Jianpu
    University of Cambridge, England.
    Blakesley, James C.
    University of Potsdam, Germany.
    Hwang, Inchan
    University of Cambridge, England.
    Li, Zhe
    University of Cambridge, England.
    Greenham, Neil C.
    University of Cambridge, England.
    Quantifying Loss Mechanisms in Polymer:Fullerene Photovoltaic Devices2012In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 2, no 8, p. 956-961Article in journal (Refereed)
    Abstract [en]

    n/a

  • 41.
    Gao, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Yuan, Y.
    Nanjing University, 210093 China.
    Wang, K. F.
    Nanjing University, 210093 China.
    Chen, X. Y.
    Nanjing University, 210093 China.
    Chen, F.
    Nanjing University, 210093 China.
    Liu, J. -M.
    Nanjing University, 210093 China.
    Preparation and photoabsorption characterization of BiFeO3 nanowires2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, no 10, p. 102506-Article in journal (Refereed)
    Abstract [en]

    Perovskite-type polycrystalline BiFeO3 (BFO) nanowires (similar to 50 nm in diameter and similar to 5 mu m in length) were synthesized using the anodized alumina template technique. An energy band gap of similar to 2.5 eV was determined from the UV-visible diffuse reflectance spectrum, and its photocatalytic ability to produce O-2 was revealed under UV irradiation. Weak ferromagnetism at room temperature and superparamagnetism at low temperature were observed for the BFO nanowires, different from the antiferromagnetic order in bulk BFO, reflecting the significant size effects on the magnetic ordering of BFO. (c) 2006 American Institute of Physics.

  • 42.
    Giovanni, David
    et al.
    Nanyang Technol Univ, Singapore; Energy Res Inst NTU ERI N, Singapore.
    Lim, Jia Wei Melvin
    Nanyang Technol Univ, Singapore.
    Yuan, Zhongcheng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Lim, Swee Sien
    Nanyang Technol Univ, Singapore.
    Righetto, Marcello
    Nanyang Technol Univ, Singapore.
    Qing, Jian
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Zhang, Qiannan
    Nanyang Technol Univ, Singapore.
    Dewi, Herlina Arianita
    Energy Res Inst NTU ERI N, Singapore.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Mhaisalkar, Subodh Gautam
    Energy Res Inst NTU ERI N, Singapore; Nanyang Technol Univ, Singapore.
    Mathews, Nripan
    Energy Res Inst NTU ERI N, Singapore; Nanyang Technol Univ, Singapore.
    Sum, Tze Chien
    Nanyang Technol Univ, Singapore.
    Ultrafast long-range spin-funneling in solution-processed Ruddlesden-Popper halide perovskites2019In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 3456Article in journal (Refereed)
    Abstract [en]

    Room-temperature spin-based electronics is the vision of spintronics. Presently, there are few suitable material systems. Herein, we reveal that solution-processed mixed-phase Ruddlesden-Popper perovskite thin-films transcend the challenges of phonon momentum-scattering that limits spin-transfer in conventional semiconductors. This highly disordered system exhibits a remarkable efficient ultrafast funneling of photoexcited spin-polarized excitons from two-dimensional (2D) to three-dimensional (3D) phases at room temperature. We attribute this efficient exciton relaxation pathway towards the lower energy states to originate from the energy transfer mediated by intermediate states. This process bypasses the omnipresent phonon momentum-scattering in typical semiconductors with stringent band dispersion, which causes the loss of spin information during thermalization. Film engineering using graded 2D/3D perovskites allows unidirectional out-of-plane spin-funneling over a thickness of similar to 600 nm. Our findings reveal an intriguing family of solution-processed perovskites with extraordinary spin-preserving energy transport properties that could reinvigorate the concepts of spin-information transfer.

  • 43.
    Giuri, Antonella
    et al.
    CNR Nanotec, Italy; Univ Salento, Italy.
    Yuan, Zhongcheng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Miao, Yanfeng
    Nanjing Tech Univ Nanjing Tech, Peoples R China.
    Wang, Jianpu
    Nanjing Tech Univ Nanjing Tech, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Sestu, Nicola
    Univ Cagliari, Italy.
    Saba, Michele
    Univ Cagliari, Italy.
    Bongiovanni, Giovanni
    Univ Cagliari, Italy.
    Colella, Silvia
    CNR Nanotec, Italy; Univ Salento, Italy.
    Corcione, Carola Esposito
    Univ Salento, Italy.
    Gigli, Giuseppe
    CNR Nanotec, Italy.
    Listorti, Andrea
    CNR Nanotec, Italy; Univ Salento, Italy.
    Rizzo, Aurora
    CNR Nanotec, Italy.
    Ultra-Bright Near-Infrared Perovskite Light-Emitting Diodes with Reduced Efficiency Roll-off2018In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 15496Article in journal (Refereed)
    Abstract [en]

    Herein, an insulating biopolymer is exploited to guide the controlled formation of micro/nano-structure and physical confinement of alpha-delta mixed phase crystalline grains of formamidinium lead iodide (FAPbI(3)) perovskite, functioning as charge carrier concentrators and ensuring improved radiative recombination and photoluminescence quantum yield (PLQY). This composite material is used to build highly efficient near-infrared (NIR) FAPbI(3) Perovskite light-emitting diodes (PeLEDs) that exhibit a high radiance of 206.7 W/sr*m(2), among the highest reported for NIR-PeLEDs, obtained at a very high current density of 1000 mA/cm(2), while importantly avoiding the efficiency roll-off effect. In depth photophysical characterization allows to identify the possible role of the biopolymer in i) enhancing the radiative recombination coefficient, improving light extraction by reducing the refractive index, or ii) enhancing the effective optical absorption because of dielectric scattering at the polymer-perovskite interfaces. Our study reveals how the use of insulating matrixes for the growth of perovskites represents a step towards high power applications of PeLEDs.

  • 44.
    He, Ximin
    et al.
    University of Cambridge, England; University of Cambridge, England.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Tu, Guoli
    University of Cambridge, England.
    Hasko, David G.
    University of Cambridge, England.
    Huettner, Sven
    University of Cambridge, England.
    Greenham, Neil C.
    University of Cambridge, England.
    Steiner, Ullrich
    University of Cambridge, England.
    Friend, Richard H.
    University of Cambridge, England.
    Huck, Wilhelm T. S.
    University of Cambridge, England; University of Cambridge, England; Radboud University of Nijmegen, Netherlands.
    Formation of Well-Ordered Heterojunctions in Polymer: PCBM Photovoltaic Devices2011In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 21, no 1, p. 139-146Article in journal (Refereed)
    Abstract [en]

    The nanoscale morphology in polymer:PCBM based photovoltaic devices is a major contributor to overall device performance. The disordered nature of the phase-separated structure, in combination with the small length scales involved and the inherent difficulty of reproducing the exact morphologies when spin-coating and annealing thin blend films, have greatly hampered the development of a detailed understanding of how morphology impacts photo voltaic device functioning. In this paper we demonstrate a double nanoimprinting process that allows the formation of nanostructured polymer: PCBM heterojunctions of composition and morphology that can be selected independently. We fabricated photovoltaic (PV) devices with extremely high densities (10(14) mm(-2)) of interpenetrating nanoscale columnar features (as small as 25 nm; at or below the exciton diffusion length) in the active layer. By comparing device results of different feature sizes and two different polymer: PCBM combinations, we demonstrate how double imprinting can be a powerful tool to systematically study different parameters in polymer photovoltaic devices.

  • 45.
    He, Ximin
    et al.
    University of Cambridge, England; University of Cambridge, England.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Tu, Guoli
    University of Cambridge, England.
    Hasko, David
    University of Cambridge, England.
    Huettner, Sven
    University of Cambridge, England.
    Steiner, Ullrich
    University of Cambridge, England; University of Freiburg, Germany.
    Greenham, Neil C.
    University of Cambridge, England.
    Friend, Richard H.
    University of Cambridge, England.
    Huck, Wilhelm T. S.
    University of Cambridge, England; University of Cambridge, England; Radboud University of Nijmegen, Netherlands.
    Formation of Nanopatterned Polymer Blends in Photovoltaic Devices2010In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 10, no 4, p. 1302-1307Article in journal (Refereed)
    Abstract [en]

    In this paper, we demonstrate a double nanoimprinting process that allows the formation of nanostructured polymer heterojunctions of composition and morphology that can be selected independently. We fabricated photovoltaic (PV) devices with extremely high densities (10(14)/mm(2)) of interpenetrating nanoscale columnar features in the active polymer blend layer. The smallest feature sizes are as small as 25 nm on a 50 nm pitch, which results in a spacing of hererojunctions at or below the exciton diffusion length. Photovoltaic devices based on double-imprinted poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2,2 diyl) (F8TBT)/poly(3-hexylthiophene) (P3HT) films are among the best polymer polymer blend devices reported to date with a power conversion efficiency (PCE, eta(e)) of 1.9%.

  • 46.
    Hou, Jianhui
    et al.
    Chinese Acad Sci, Peoples R China.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Friend, Richard H.
    Cavendish Lab, England.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Organic solar cells based on non-fullerene acceptors2018In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 17, no 2, p. 119-128Article, review/survey (Refereed)
    Abstract [en]

    Organic solar cells (OSCs) have been dominated by donor: acceptor blends based on fullerene acceptors for over two decades. This situation has changed recently, with non-fullerene (NF) OSCs developing very quickly. The power conversion efficiencies of NF OSCs have now reached a value of over 13%, which is higher than the best fullerene-based OSCs. NF acceptors show great tunability in absorption spectra and electron energy levels, providing a wide range of new opportunities. The coexistence of low voltage losses and high current generation indicates that new regimes of device physics and photophysics are reached in these systems. This Review highlights these opportunities made possible by NF acceptors, and also discuss the challenges facing the development of NF OSCs for practical applications.

  • 47.
    Jia, Ping
    et al.
    Nanjing Univ, Peoples R China.
    Wang, Yinlong
    Nanjing Univ, Peoples R China.
    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.
    Gong, Jijun
    Nanjing Univ, Peoples R China.
    Lin, Lin
    Nanjing Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Liu, J-M
    Nanjing Univ, Peoples R China.
    Electronic phase engineering induced thermoelectric enhancement in manganites2018In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 124, no 3, article id 034501Article in journal (Refereed)
    Abstract [en]

    The nano-structuring engineering and the introduction of magnetic scattering are effective ways to enhance the thermoelectric performance. In this work, we use the magnetic treatments on La0.4Pr0.225Ca0.375MnO3 to demonstrate that the electronic phase engineering can enhance the thermoelectric performance by simultaneously reducing the thermal conductivity and raising the power factor in a strongly correlated electron system. This study indicates that the magnetic treatment changes the phase separation state and impedes the growth of ferromagnetic metal (FMM) phase. The reduction of FMM phase suppresses the bipolar effect, which raises the Seebeck coefficient and the power factor, reduces the thermal conductivity, and therefore enhances the thermoelectric performance.

  • 48.
    Ke, You
    et al.
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Wang, Nana
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Kong, Decheng
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Cao, Yu
    Nanjing Tech Univ NanjingTech, Peoples R China.
    He, Yarong
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Zhu, Lin
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Wang, Yuming
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Xue, Chen
    Northwestern Polytech Univ, Peoples R China.
    Peng, Qiming
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Huang, Wei
    Nanjing Tech Univ NanjingTech, Peoples R China; Northwestern Polytech Univ, Peoples R China.
    Wang, Jianpu
    Nanjing Tech Univ NanjingTech, Peoples R China.
    Defect Passivation for Red Perovskite Light-Emitting Diodes with Improved Brightness and Stability2019In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 10, no 3, p. 380-385Article in journal (Refereed)
    Abstract [en]

    Efficient and stable red perovskite light-emitting diodes (PeLEDs) are important for realizing full-color display and lighting. Red PeLEDs can be achieved either by mixed-halide or low-dimensional perovskites. However, the device performance, especially the brightness, is still low owing to phase separation or poor charge transport issues. Here, we demonstrate red PeLEDs based on three-dimensional (3D) mixed-halide perovskites where the defects are passivated by using 5-aminovaleric acid. The red PeLEDs with an emission peak at 690 nm exhibit an external quantum efficiency of 8.7% and a luminance of 1408 cd m(-2). A maximum luminance of 8547 cd m(-2) can be further achieved as tuning the emission peak to 662 nm, representing the highest brightness of red PeLEDs. Moreover, those LEDs exhibit a half-life of up to 8 h under a high constant current density of 100 mA cm(-2), which is over 10 times improvement compared to literature results.

  • 49.
    Kroon, Renee
    et al.
    University of S Australia, Australia Chalmers, Sweden .
    Diaz de Zerio Mendaza, Amaia
    Chalmers, Sweden .
    Himmelberger, Scott
    Stanford University, CA 94305 USA .
    Bergqvist, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Backe, Olof
    Chalmers, Sweden .
    Couto Faria, Gregorio
    Stanford University, CA 94305 USA University of Sao Paulo, Brazil .
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Obaid, Abdulmalik
    Wake Forest University, NC 27106 USA .
    Zhuang, Wenliu
    Chalmers, Sweden .
    Gedefaw, Desta
    Chalmers, Sweden .
    Olsson, Eva
    Chalmers, Sweden .
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Salleo, Alberto
    Stanford University, CA 94305 USA .
    Muller, Christian
    Chalmers, Sweden .
    Andersson, Mats R.
    University of S Australia, Australia Chalmers, Sweden .
    A New Tetracyclic Lactam Building Block for Thick, Broad-Bandgap Photovoltaics2014In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, no 33, p. 11578-11581Article in journal (Refereed)
    Abstract [en]

    A new tetracyclic lactam building block for polymer semiconductors is reported that was designed to combine the many favorable properties that larger fused and/or amide-containing building blocks can induce, including improved solid-state packing, high charge carrier mobility, and improved charge separation. Copolymerization with thiophene resulted in a semicrystalline conjugated polymer, PTNT, with a broad bandgap of 2.2 eV. Grazing incidence wide-angle X-ray scattering of PTNT thin films revealed a strong tendency for face-on pi-stacking of the polymer backbone, which was retained in PTNT:firllerene blends. Corresponding solar cells featured a high open-circuit voltage of 0.9 V, a fill factor around 0.6, and a power conversion efficiency as high as 596 for greater than200 nm thick active layers, regardless of variations in blend stoichiometry and nanostructure. Moreover, efficiencies of greater than4% could be retained when thick active layers of similar to 400 rim were employed. Overall, these values are the highest reported for a conjugated polymer with such a broad bandgap and are unprecedented in materials for tandem and particularly ternary blend photovoltaics. Hence, the newly developed tetracyclic lactam unit has significant potential as a conjugated building block in future organic electronic materials.

  • 50.
    Kumawat, Naresh Kumar
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Liu, Xiaoke
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Kabra, Dinesh
    Indian Inst Technol, India.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Blue perovskite light-emitting diodes: progress, challenges and future directions2019In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 5, p. 2109-2120Article, review/survey (Refereed)
    Abstract [en]

    Metal halide perovskites have excellent optical and electrical properties and can be easily processed via low-cost solution-based techniques like blade-coating and inkjet printing, promising a bright future for various optoelectronic applications. Recently, encouraging progress has been made in perovskite light-emitting diodes (PeLEDs). Green, red, and near-infrared PeLEDs have achieved high external quantum efficiencies of more than 20%. However, as historically blue electroluminescence remains challenging in all previous LED technologies, we are witnessing a similar case with the development of blue PeLEDs, an essential part of displays and solid-state lighting, which lag far behind those of their counterparts. Herein, we review the recent progress of blue PeLEDs and discuss the main challenges including colour instability, poor photoluminescence efficiency and emission quenching by interlayers. Future directions are provided to facilitate the development of efficient blue PeLEDs.

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