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  • 1.
    Ali Ahmad, Syed Ossama
    et al.
    Govt Coll Univ, Pakistan.
    Ashfaq, Atif
    Govt Coll Univ, Pakistan.
    Akbar, Muhammad Usama
    Govt Coll Univ, Pakistan.
    Ikram, Mujtaba
    Univ Punjab, Pakistan.
    Khan, Karim
    Dongguan Univ Technol DGUT, Peoples R China.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Ikram, Muhammad
    Govt Coll Univ, Pakistan.
    Mahmood, Asif
    Univ Sydney, Australia.
    Application of two-dimensional materials in perovskite solar cells: recent progress, challenges, and prospective solutions2021In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 9, no 40, p. 14065-14092Article, review/survey (Refereed)
    Abstract [en]

    Perovskite solar cells (per-SCs) with high performance and cost-effective solution processing have been the center of interest for researchers in the past decade. Power conversion efficiencies (PCEs) have been gradually improved up to 25.2% with relatively improved stability, which is an unparalleled progress in all generations of solar cell (SC) technology. However, there are still some prevailing challenges regarding the stability and upscaling of these promising devices. Recently, 2D layered materials (LMs) have been extensively explored to overcome the prevailing challenges of poor stability (under moisture, light soaking and high temperature), halide segregation, hysteresis, involvement of toxic materials (i.e., lead), and upscaling of devices. A critical review addressing the recent developments in the use of 2D materials, especially transition metal dichalcogenides (TMDCs), is hence necessary. The development of novel synthesis and deposition techniques including liquid-metal synthesis and ultrasonic assisted spray pyrolysis has offered more efficient fabrication of 2D-LMs with controlled thickness and morphology. Effective functionalization approaches to increase the dispersability of 2D-LMs in non-polar solvents has boosted their potential application in solar cell technology as well. Moreover, compositing 2D TMDCs with suitable organic/inorganic compounds has enabled superior charge kinetics in all functional parts of per-SCs. In addition, newly developed materials such as graphyne and graphdyine along with 2D metal organic frameworks (MOFs) and covalent organic frameworks (COFs) have been employed in per-SCs to achieve PCEs up to 20%. This review summarizes the recent progress and challenges in the application of 2D-LMs in per-SCs and outlines the future pathways to further extend the PCE of per-SCs beyond 25%. This review particularly focuses on 2D-LMs as electrode materials and additives, the underlying charge (electron-hole) transport phenomenon in the functional layers, and their chemical and structural stability.

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  • 2.
    An, Xiaoqiang
    et al.
    Tsinghua Univ, Peoples R China.
    Wei, Tingcha
    Tsinghua Univ, Peoples R China; Nanjing Univ Aeronaut & Astronaut, Peoples R China.
    Ding, Peijia
    Beihang Univ, Peoples R China.
    Liu, Li-Min
    Beihang Univ, Peoples R China.
    Xiong, Lunqiao
    UCL, England.
    Tang, Junwang
    UCL, England.
    Ma, Jiani
    Shanxi Normal Univ, Peoples R China.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Liu, Huijuan
    Tsinghua Univ, Peoples R China.
    Qu, Jiuhui
    Tsinghua Univ, Peoples R China.
    Sodium-Directed Photon-Induced Assembly Strategy for Preparing Multisite Catalysts with High Atomic Utilization Efficiency2023In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 145, no 3, p. 1759-1768Article in journal (Refereed)
    Abstract [en]

    Integrating different reaction sites offers new prospects to address the difficulties in single-atom catalysis, but the precise regulation of active sites at the atomic level remains challenging. Here, we demonstrate a sodium-directed photon-induced assembly (SPA) strategy for boosting the atomic utilization efficiency of single-atom catalysts (SACs) by constructing multifarious Au sites on TiO2 substrate. Na+ was employed as the crucial cement to direct Au single atoms onto TiO2, while the light-induced electron transfer from excited TiO2 to Au(Na+) ensembles contributed to the self-assembly formation of Au nanoclusters. The synergism between plasmonic near-field and Schottky junction enabled the cascade electron transfer for charge separation, which was further enhanced by oxygen vacancies in TiO2. Our dual-site photocatalysts exhibited a nearly 2 orders of magnitude improvement in the hydrogen evolution activity under simulated solar light, with a striking turnover frequency (TOF) value of 1533 h(-1) that exceeded other Au/TiO2-based photocatalysts reported. Our SPA strategy can be easily extended to prepare a wide range of metal-coupled nanostructures with enhanced performance for diverse catalytic reactions. Thus, this study provides a well-defined platform to extend the boundaries of SACs for multisite catalysis through harnessing metal-support interactions.

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  • 3.
    Ikram, Muhammad
    et al.
    Govt Coll Univ Lahore, Pakistan.
    Malik, Rumesa
    Riphah Int Univ, Pakistan.
    Raees, Rimsha
    Riphah Int Univ, Pakistan.
    Imran, Muhammad
    Govt Coll Univ Faisalabad, Pakistan.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Ali, Salamat
    Riphah Int Univ, Pakistan.
    Khan, Maaz
    Southeast Univ, Peoples R China.
    Khan, Qasim
    Southeast Univ, Peoples R China.
    Maqbool, Muhammad
    Univ Alabama Birmingham, AL 35294 USA.
    Recent advancements and future insight of lead-free non-toxic perovskite solar cells for sustainable and clean energy production: A review2022In: Vol. 53, article id 102433Article, review/survey (Refereed)
    Abstract [en]

    Production and management of clean energy in a sustainable manner is a global need. Several methods of energy production have been explored but some of them are accompanied with environmental hazards and toxic materials. One of those several means of sustainable energy production is a perovskite solar cell. Perovskite solar cells have received interest for photovoltaic applications attributed to their verified over 25% power conversion efficiency. Because of the high toxicity associated with lead, it seems a pressing need to clean and remove toxic lead from currently available and future inorganic Perovskite solar cells. Environmental-health hazards are posed by lead-based compounds and devices available for use. This review focuses on the development of lead-free non-toxic perovskite materials based solar cells and other devices. To solve the lead associated toxicity problem, lead can be substituted with nontoxic and environmentally friendly metals like Ti, Sn, Sb, Ge, Bi, and Ag. To further enhance the stability of lead-free perovskites, all-inorganic lead-free perovskites have recently gotten considerable attention. In numerical simulation, the CsSnI3 based perovskite solar cell has the highest power conversion efficiency of 28.97% among all the lead-free perovskite based devices. Extensive review of environmentally friendly and toxicity free perovskites and their applications has been performed. The advantages of lead substituted metals have been discussed. Lastly, critical analysis and discusses is reported on the progress to enhance the efficiency and stability of lead-free perovskite solar cells and devices by energy-band engineering and inorganic transport layers.

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  • 4.
    Ji, Fuxiang
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Uppsala Univ, Sweden.
    Boschloo, Gerrit
    Uppsala Univ, Sweden.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Challenges and Progress in Lead-Free Halide Double Perovskite Solar Cells2023In: Solar RRL, E-ISSN 2367-198X, Vol. 7, no 6, article id 2201112Article in journal (Refereed)
    Abstract [en]

    Lead-free halide double perovskites (HDPs) with a chemical formula of A(2)B(+)B(3+)X(6) are booming as attractive alternatives to solve the toxicity issue of lead-based halide perovskites (APbX(3)). HDPs show excellent stability, a wide range of possible combinations, and attractive optoelectronic features. Although a number of novel HDPs have been studied, the power conversion efficiency of the state-of-the-art double perovskite solar cell is still far inferior to that of the dominant Pb-based ones. Understanding the fundamental challenges is essential for further increasing device efficiency. In this review, HDPs with attractive electronic and optical properties are focused on, and current challenges in material properties and device fabrication that limit high-efficiency photovoltaics are analyzed. Finally, the promising approaches and views to overcome these bottlenecks are highlighted.

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  • 5.
    Ji, Fuxiang
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Huang, Yuqing
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Kobera, Libor
    Czech Acad Sci, Czech Republic.
    Xie, Fangyan
    Sun Yat Sen Univ, Peoples R China.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Abbrent, Sabina
    Czech Acad Sci, Czech Republic.
    Brus, Jiri
    Czech Acad Sci, Czech Republic.
    Yin, Chunyang
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Natl Univ Sci & Technol MISIS, Russia.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    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.
    Near-Infrared Light-Responsive Cu-Doped Cs2AgBiBr62020In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 30, no 51, article id 2005521Article in journal (Refereed)
    Abstract [en]

    Lead-free halide double perovskites (A(2)B(I)B(III)X(6)) with attractive optical and electronic features are considered to be a promising candidate to overcome the toxicity and stability issues of lead halide perovskites (APbX(3)). However, their poor absorption profiles limit device performance. Here the absorption band edge of Cs(2)AgBiBr(6)double perovskite to the near-infrared range is significantly broadened by developing doped double perovskites, Cs-2(Ag:Cu)BiBr6. The partial replacement of Ag ions by Cu ions in the crystal lattice is confirmed by the X-ray photoelectron spectroscopy (XPS) and solid-state nuclear magnetic resonance (ssNMR) measurements. Cu doping barely affects the bandgap of Cs2AgBiBr6; instead it introduces subbandgap states with strong absorption to the near-infrared range. More interestingly, the near-infrared absorption can generate band carriers upon excitation, as indicated by the photoconductivity measurement. This work sheds new light on the absorption modulation of halide double perovskites for future efficient optoelectronic devices.

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  • 6.
    Ji, Fuxiang
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ning, Weihua
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Wang, Linqin
    KTH Royal Inst Technol, Sweden.
    Yin, Chunyang
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Mendoza Figueroa, José Silvestre
    Linköping University, Department of Physics, Chemistry and Biology, Biophysics and bioengineering. Linköping University, Faculty of Science & Engineering.
    Christensen, Christian Kolle
    DESY, Germany.
    Etter, Martin
    DESY, Germany.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Biophysics and bioengineering. Linköping University, Faculty of Science & Engineering.
    Sun, Licheng
    KTH Royal Inst Technol, Sweden; Dalian Univ Technol, Peoples R China.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Natl Univ Sci and Technol MISIS, Russia.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Lead-Free Halide Double Perovskite Cs2AgBiBr6with Decreased Band Gap2020In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 59, no 35, p. 15191-15194Article in journal (Refereed)
    Abstract [en]

    Environmentally friendly halide double perovskites with improved stability are regarded as a promising alternative to lead halide perovskites. The benchmark double perovskite, Cs2AgBiBr6, shows attractive optical and electronic features, making it promising for high-efficiency optoelectronic devices. However, the large band gap limits its further applications, especially for photovoltaics. Herein, we develop a novel crystal-engineering strategy to significantly decrease the band gap by approximately 0.26 eV, reaching the smallest reported band gap of 1.72 eV for Cs(2)AgBiBr(6)under ambient conditions. The band-gap narrowing is confirmed by both absorption and photoluminescence measurements. Our first-principles calculations indicate that enhanced Ag-Bi disorder has a large impact on the band structure and decreases the band gap, providing a possible explanation of the observed band-gap narrowing effect. This work provides new insights for achieving lead-free double perovskites with suitable band gaps for optoelectronic applications.

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  • 7.
    Ji, Fuxiang
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Zhang, Bin
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Linqin
    School of Science Westlake University Hangzhou, P.R. China.
    Miao, Xiaohe
    Westlake University Hangzhou, P.R. China.
    Ning, Weihua
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Soochow University Suzhou, P. R. China.
    Zhang, Muyi
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Cai, Xinyi
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Bakhit, Babak
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Magnuson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ren, Xiaoming
    State Key Laboratory of Materials‐Oriented Chemical Engineering and College of Chemistry and Molecular Engineering Nanjing Tech University Nanjing, P.R. China.
    Sun, Licheng
    Center of Artificial Photosynthesis for Solar Fuels, School of Science Westlake University Hangzhou,P.R. China.
    Fahlman, Mats
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials.
    Chen, Weimin
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials.
    Simak, Sergei I
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Uppsala University Uppsala SE‐75120 Sweden.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Remarkable Thermochromism in the Double Perovskite Cs2NaFeCl62023In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, article id 2301102Article in journal (Refereed)
    Abstract [en]

    Lead-free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light-yellow to black over a temperature range of 10 to 423 K is investigated. First-principles, density functional theory (DFT)-based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron–phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK−1 based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group-IV, III–V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials.

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  • 8.
    Ji, Fuxiang
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Kobera, Libor
    Czech Acad Sci, Czech Republic.
    Abbrent, Sabina
    Czech Acad Sci, Czech Republic.
    Brus, Jiri
    Czech Acad Sci, Czech Republic.
    Ning, Weihua
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Nanjing Tech Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    The atomic-level structure of bandgap engineered double perovskite alloys Cs2AgIn1-xFexCl62021In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 12, no 5, p. 1730-1735Article in journal (Refereed)
    Abstract [en]

    Although lead-free halide double perovskites are considered as promising alternatives to lead halide perovskites for optoelectronic applications, state-of-the-art double perovskites are limited by their large bandgap. The doping/alloying strategy, key to bandgap engineering in traditional semiconductors, has also been employed to tune the bandgap of halide double perovskites. However, this strategy has yet to generate new double perovskites with suitable bandgaps for practical applications, partially due to the lack of fundamental understanding of how the doping/alloying affects the atomic-level structure. Here, we take the benchmark double perovskite Cs2AgInCl6 as an example to reveal the atomic-level structure of double perovskite alloys (DPAs) Cs2AgIn1-xFexCl6 (x = 0-1) by employing solid-state nuclear magnetic resonance (ssNMR). The presence of paramagnetic alloying ions (e.g. Fe3+ in this case) in double perovskites makes it possible to investigate the nuclear relaxation times, providing a straightforward approach to understand the distribution of paramagnetic alloying ions. Our results indicate that paramagnetic Fe3+ replaces diamagnetic In3+ in the Cs2AgInCl6 lattice with the formation of [FeCl6](3-)center dot[AgCl6](5-) domains, which show different sizes and distribution modes in different alloying ratios. This work provides new insights into the atomic-level structure of bandgap engineered DPAs, which is of critical significance in developing efficient optoelectronic/spintronic devices.

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  • 9.
    Ji, Fuxiang
    et al.
    Department of Chemistry‐Ångström Laboratory Physical Chemistry Uppsala University Uppsala SE‐751 20 Sweden.
    Zhang, Bin
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Boschloo, Gerrit
    Department of Chemistry‐Ångström Laboratory Physical Chemistry Uppsala University Uppsala SE‐751 20 Sweden.
    Amine Gas‐Induced Reversible Optical Bleaching of Bismuth‐Based Lead‐Free Perovskite Thin Films2023In: Advanced Science, E-ISSN 2198-3844, Vol. 11, no 4, article id 2306391Article in journal (Refereed)
    Abstract [en]

    Reversible optical property changes in lead-free perovskites have recently received great interest due to their potential applications in smart windows, sensors, data encryption, and various on-demand devices. However, it is challenging to achieve remarkable color changes in their thin films. Here, methylamine gas (CH3NH2, MA0) induced switchable optical bleaching of bismuth (Bi)-based perovskite films is demonstrated for the first time. By exposure to an MA0 atmosphere, the color of Cs2AgBiBr6 (CABB) films changes from yellow to transparent, and the color of Cs3Bi2I9 (CBI) films changes from dark red to transparent. More interestingly, the underlying reason is found to be the interactions between MA0 and Bi3+ with the formation of an amorphous liquefied transparent intermediate phase, which is different from that of lead-based perovskite systems. Moreover, the generality of this approach is demonstrated with other amine gases, including ethylamine (C2H5NH2, EA0) and butylamine (CH3(CH2)3NH2, BA0), and another compound, Cs3Sb2I9, by observing a similar reversible optical bleaching phenomenon. The potential for the application of CABB and CBI films in switchable smart windows is investigated. This study provides valuable insights into the interactions between amine gases and lead-free perovskites, opening up new possibilities for high-efficiency optoelectronic and stimuli-responsive applications of these emerging Bi-based materials.

  • 10.
    Li, Zhiqi
    et al.
    Jilin Univ, Peoples R China.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Liu, Chunyu
    Jilin Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Shen, Liang
    Jilin Univ, Peoples R China.
    Guo, Wenbin
    Jilin Univ, Peoples R China.
    Efficient perovskite solar cells enabled by ion-modulated grain boundary passivation with a fill factor exceeding 84%2019In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, no 39, p. 22359-22365Article in journal (Refereed)
    Abstract [en]

    Alkali metal cation modulation toward high-electronic-quality perovskite films requires strict control over trap densities in the devices. By introducing tailor-made potassium cation (K+)-functionalized carbon nanodots (CNDs@K) into the perovskite precursor solution, we succeeded in defect passivation and crystallization control of the perovskite film. X-ray diffraction indicated that the binding effect of carbon dots confined the K+ ions in the grain boundary and prevented excessive cations from occupying interstitial sites, thereby reducing the microstrain of the polycrystalline film. Consequently, the synergistic effect of the tailored crystal size and suppressed grain boundary defects could reduce the charge trap density, facilitate charge generation, and lengthen the carrier lifetime, leading to a boosted efficiency of 21.01% with a high fill factor of 84%. This performance is among the best reported for carbon dot-doped PSCs.

  • 11.
    Ning, Weihua
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Nanjing Tech Univ, Peoples R China.
    Zhao, Xin-Gang
    Jilin Univ, Peoples R China.
    Klarbring, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Bai, Sai
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ji, Fuxiang
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Tao, Youtian
    Nanjing Tech Univ, Peoples R China.
    Ren, Xiao-Ming
    Nanjing Tech Univ, Peoples R China.
    Zhang, Lijun
    Jilin Univ, Peoples R China.
    Huang, Wei
    Nanjing Tech Univ, Peoples R China.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Natl Univ Sci and Technol MISIS, Russia.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Thermochromic Lead-Free Halide Double Perovskites2019In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 29, no 10, article id 1807375Article in journal (Refereed)
    Abstract [en]

    Lead-free halide double perovskites with diverse electronic structures and optical responses, as well as superior material stability show great promise for a range of optoelectronic applications. However, their large bandgaps limit their applications in the visible light range such as solar cells. In this work, an efficient temperature-derived bandgap modulation, that is, an exotic fully reversible thermochromism in both single crystals and thin films of Cs2AgBiBr6 double perovskites is demonstrated. Along with the thermochromism, temperature-dependent changes in the bond lengths of Ag Symbol of the Klingon Empire Br (R-Ag Symbol of the Klingon Empire Br) and Bi Symbol of the Klingon Empire Br (R-Bi Symbol of the Klingon Empire Br) are observed. The first-principle molecular dynamics simulations reveal substantial anharmonic fluctuations of the R-Ag Symbol of the Klingon Empire Br and R-Bi Symbol of the Klingon Empire Br at high temperatures. The synergy of anharmonic fluctuations and associated electron-phonon coupling, and the peculiar spin-orbit coupling effect, is responsible for the thermochromism. In addition, the intrinsic bandgap of Cs2AgBiBr6 shows negligible changes after repeated heating/cooling cycles under ambient conditions, indicating excellent thermal and environmental stability. This work demonstrates a stable thermochromic lead-free double perovskite that has great potential in the applications of smart windows and temperature sensors. Moreover, the findings on the structure modulation-induced bandgap narrowing of Cs2AgBiBr6 provide new insights for the further development of optoelectronic devices based on the lead-free halide double perovskites.

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  • 12.
    Ning, Weihua
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Nanjing Tech Univ, Peoples R China.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Wu, Bo
    Nanyang Technol Univ, Singapore.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. 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.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Tao, Youtian
    Nanjing Tech Univ, Peoples R China.
    Liu, Jun-Ming
    Nanjing Univ, Peoples R China.
    Huang, Wei
    Nanjing Tech Univ, Peoples R China.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sum, Tze Chien
    Nanyang Technol Univ, Singapore.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Long Electron-Hole Diffusion Length in High-Quality Lead-Free Double Perovskite Films2018In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 30, no 20, article id 1706246Article in journal (Refereed)
    Abstract [en]

    Developing environmentally friendly perovskites has become important in solving the toxicity issue of lead-based perovskite solar cells. Here, the first double perovskite (Cs2AgBiBr6) solar cells using the planar structure are demonstrated. The prepared Cs2AgBiBr6 films are composed of high-crystal-quality grains with diameters equal to the film thickness, thus minimizing the grain boundary length and the carrier recombination. These high-quality double perovskite films show long electron-hole diffusion lengths greater than 100 nm, enabling the fabrication of planar structure double perovskite solar cells. The resulting solar cells based on planar TiO2 exhibit an average power conversion efficiency over 1%. This work represents an important step forward toward the realization of environmentally friendly solar cells and also has important implications for the applications of double perovskites in other optoelectronic devices.

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  • 13.
    Obila, Jorim Okoth
    et al.
    Univ Nairobi, Kenya.
    Lei, Hongwei
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Huazhong Agr Univ, Peoples R China.
    Ayieta, Elijah Omollo
    Univ Nairobi, Kenya.
    Ogacho, Alex Awuor
    Univ Nairobi, Kenya.
    Aduda, Bernard O.
    Univ Nairobi, Kenya.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Optoelectronic property refinement of FASnI(3) films for photovoltaic application2021In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 300, article id 130099Article in journal (Refereed)
    Abstract [en]

    Tin (Sn) is a promising substitute for lead (Pb) in organic-inorganic hybrid halide perovskite-photovoltaic devices, but it is prone to delivering low power conversion efficiencies (PCEs) due to the poor quality of Snperovskite films. In this work, anilinium hypophosphite (AHP) co-additive is used to fabricate high-quality FASnI3 (FA+: formamidinium) perovskite films with suppressed phase-segregation and prolonged charge carrier lifetime. Perovskite films containing 0.05 M AHP are used to fabricate solar cells and deliver improved power conversion efficiency (PCE) of up to 5.48% (control devices: 4.04%). AHP eliminates the phase separation caused by SnF2 in the absorber, leading to films with enhanced optoelectronic properties, hence the high performance of AHP-based devices.

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  • 14.
    Obila, Jorim Okoth
    et al.
    Univ Nairobi, Kenya.
    Lei, Hongwei
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Huazhong Agr Univ, Peoples R China.
    Ayieta, Elijah Omolo
    Univ Nairobi, Kenya.
    Ogacho, Alex Awuor
    Univ Nairobi, Kenya.
    Aduda, Bernard O.
    Univ Nairobi, Kenya.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Improving the efficiency and stability of tin-based perovskite solar cells using anilinium hypophosphite additive2021In: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 45, no 18, p. 8092-8100Article in journal (Refereed)
    Abstract [en]

    Tin (Sn) is a potential replacement for lead in organic-inorganic perovskite solar cell (PVSC) technology due to the attractive optoelectronic properties of Sn-perovskites. However, the poor stability of Sn2+ ions is still the main hindrance for achieving highly stable and efficient Sn-based PVSCs. In this work, anilinium hypophosphite (AHP) is introduced as a co-additive into a Sn-absorber perovskite precursor containing the tin fluoride (SnF2) additive. The incorporation of the AHP additive not only prohibits the phase separation of SnF2 but also passivates the perovskite films and finally results in absorbers with superior structural and optoelectronic properties. The underlying reason is related to the formation of a double-salt complex (Sn(H2PO2)(2)center dot SnF2) through the interaction between AHP and SnF2. The high quality of the absorber film induced by AHP delivers an improved device power conversion efficiency (PCE) with a higher open-circuit voltage than those without the AHP additive. More importantly, the device with the AHP additive can retain up to 97% of its PCE after 30 days of storage in a glovebox.

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  • 15.
    Ponseca, Carlito
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Arlauskas, Andrius
    Ctr Phys Sci and Technol, Lithuania.
    Yu, Hongling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Nevinskas, Ignas
    Ctr Phys Sci and Technol, Lithuania.
    Duda, Eimantas
    Ctr Phys Sci and Technol, Lithuania.
    Vaicaitis, Virgilijus
    Vilnius Univ, Lithuania.
    Eriksson, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Bergqvist, Jonas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Liu, Xiaoke
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Krotkus, Arunas
    Ctr Phys Sci and Technol, Lithuania.
    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.
    Pulsed Terahertz Emission from Solution-Processed Lead Iodide Perovskite Films2019In: ACS Photonics, E-ISSN 2330-4022, Vol. 6, no 5, p. 1175-1181Article in journal (Refereed)
    Abstract [en]

    We report pulsed terahertz (THz) emission from solution-processed metal halide perovskite films with electric field 1 order of magnitude lower than p-InAs, an efficient THz emitter. Such emission is enabled by a unique combination of efficient charge separation, high carrier mobilities, and more importantly surface defects. The mechanism of generation was identified by investigating the dependence of the THz electric field amplitude on surface defect densities, excess charge carriers, excitation intensity and energy, temperature, and external electric field. We also show for the first time THz emission from a curved surface, which is not possible for any crystalline semiconductor and paves the way to focus high-intensity sources. These results represent a possible new direction for perovskite optoelectronics and for THz emission spectroscopy as a complementary tool in investigating surface defects on metal halide perovskites, of fundamental importance in the optimization of solar cells and light-emitting diodes.

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  • 16.
    Sakkaki, Fahimeh
    et al.
    Ferdowsi Univ Mashhad, Iran.
    Roknabadi, Mahmood Rezaee
    Ferdowsi Univ Mashhad, Iran.
    Arabi, Hadi
    Ferdowsi Univ Mashhad, Iran.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Comparison of alkali metal cationmetal cation (Rb/K) doping effect on the structural, optical and photovoltaic behavior of methylammonium lead triiodide perovskite thin films2022In: Optik (Stuttgart), ISSN 0030-4026, E-ISSN 1618-1336, Vol. 250, article id 168294Article in journal (Refereed)
    Abstract [en]

    Metal cation doping is an established strategy to increase the efficiency of perovskite solar cells. However, the underlying mechanism is less discussed regarding the doping site. In this paper, the effect of rubidium/potassium as dopant has been evaluated on the CH3NH3PbI3 (MAPbI(3)) perovskite lattice. At the 5% doping level, K cations have significantly improved photovoltaic properties by promoting crystallinity, releasing the strain, reducing the trap states, and boosting all key photovoltaic parameters. Moreover, this study provides a rough description of Rb/K doping mechanisms in the MAPbI(3) lattice, where K cations occupy the interstitial sites while both interstitial and substitutional occupancies may occur for Rb cations. Our findings help to adjust the properties of perovskite layers to design new materials with better photovoltaic performance.

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  • 17.
    Wang, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Bai, Sai
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Tress, Wolfgang
    Laboratory of Photomolecular Science (LSPM), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
    Hagfeldt, Anders
    Laboratory of Photomolecular Science (LSPM), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Defects engineering for high-performance perovskite solar cells2018In: npj Flexible Electronics, ISSN 2397-4621, Vol. 2, no 1, article id 22Article in journal (Refereed)
    Abstract [en]

    Metal halide perovskites have achieved great success in photovoltaic applications during the last few years. The solar to electrical power conversion efficiency (PCE) of perovskite solar cells has been rapidly improved from 3.9% to certified 22.7% due to the extensive efforts on film deposition methods, composition and device engineering. Further investigation on eliminating the defect states in perovskite absorbers is necessary to push forward the PCE of perovskite solar cells approaching the Shockley-Queisser limit. In this review, we summarize the defect properties in perovskite films and present methodologies to control the defects density, including the growth of large size crystals, photo-curing method, grain boundary and surface passivation, and modification of the substrates. We also discuss the defects-related stability and hysteresis issues and highlight the current challenges and opportunities in defects control of perovskite films.

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  • 18.
    Wang, Feng
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Kumar, Sunil
    Indian Inst Technol Delhi, India.
    Functional Thin Films for Perovskite Solar Cells2022In: Coatings, ISSN 2079-6412, Vol. 12, no 7, article id 952Article in journal (Other academic)
    Abstract [en]

    n/a

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  • 19.
    Wang, Feng
    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.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Fundamentals of solar cells and light-emitting diodes2019In: Advanced nanomaterials for solar cells and light emitting diodes / [ed] Feng Gao, Amsterdam: Elsevier , 2019, p. 1-35Chapter in book (Other academic)
    Abstract [en]

    This chapter focuses on introducing basic concepts in solar cell and light-emitting diode (LED) devices. First, the fundamental knowledge about semiconductors and several important materials related to solar cells and LEDs is introduced to help the reader understand the working principle of devices. Second, we describe the working principle and basic terms involving solar cells, the energy loss processes, and several strategies for high-efficiency solar cell devices. Finally, we present the basic terms and the device structure of LEDs, as well as some approaches for high-efficiency white LEDs.

  • 20.
    Wang, Xin
    et al.
    Shanghai Jiao Tong Univ, Peoples R China.
    Qiu, Yuankun
    Shanghai Jiao Tong Univ, Peoples R China.
    Wang, Luyao
    Shanghai Jiao Tong Univ, Peoples R China.
    Zhang, Tiankai
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zhu, Lei
    Shanghai Jiao Tong Univ, Peoples R China.
    Shan, Tong
    Shanghai Jiao Tong Univ, Peoples R China.
    Wang, Yong
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Jiang, Jinkun
    Shanghai Jiao Tong Univ, Peoples R China.
    Kong, Lingti
    Shanghai Jiao Tong Univ, Peoples R China.
    Zhong, Hongliang
    Shanghai Jiao Tong Univ, Peoples R China.
    Yu, Haomiao
    Beijing Jiaotong Univ, Peoples R China.
    Liu, Feng
    Shanghai Jiao Tong Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Chen, Chun-Chao
    Shanghai Jiao Tong Univ, Peoples R China.
    Organic nanocrystals induced surface passivation towards high-efficiency and stable perovskite solar cells2021In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 89, article id 106445Article in journal (Refereed)
    Abstract [en]

    Surface passivation has played a critical role for efficient and stable perovskite solar cells by reducing surface defects, promoting charge transport, and preventing the penetration of degrading agents. State-of-the-art passivation approaches mainly rely on the formation of a two-dimensional (2D) perovskite layer or the deposition of an ultrathin layer based on the molecular design. Here, we demonstrated a novel nanocrystal-pinning passivation by dripping 2-bromoethyltrimethylammonium bromide (BETAB) colloidal solution onto perovskite films. Theoretical simulation and kinds of experimental results confirm that BETAB nanocrystals can effectively reduce the defect density of perovskite films. Impressively, the resulting FA1-xMAxPbI3 based planar devices exhibit a champion power conversion efficiency (PCE) of 23.04% (certified: 22.10%) with a voltage loss of only 390 mV. Besides, the BETAB nanocrystals could simultaneously increase the hydrophobic property of perovskite films and prevent the reaction and formation of 2D perovskites during device operation. Correspondingly, the resulted devices exhibit excellent stability under moisture, heating, and operational tracking conditions.

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  • 21.
    Wang, Yu
    et al.
    Jiaxing Univ, Peoples R China; Hangzhou Dianzi Univ, Peoples R China.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Song, Jiaxing
    Jiaxing Univ, Peoples R China.
    Ye, Jingchuan
    Jiaxing Univ, Peoples R China; Hangzhou Dianzi Univ, Peoples R China.
    Cao, Jieying
    Jiaxing Univ, Peoples R China.
    Yin, Xinxing
    Jiaxing Univ, Peoples R China.
    Su, Zhen
    Jiaxing Univ, Peoples R China.
    Jin, Yingzhi
    Jiaxing Univ, Peoples R China.
    Hu, Lin
    Jiaxing Univ, Peoples R China.
    Zuilhof, Han
    Jiaxing Univ, Peoples R China.
    Li, Zaifang
    Jiaxing Univ, Peoples R China.
    Yan, Wensheng
    Hangzhou Dianzi Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Ethyl Thioglycolate Assisted Multifunctional Surface Modulation for Efficient and Stable Inverted Perovskite Solar Cells2024In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028Article in journal (Refereed)
    Abstract [en]

    As the core component of sandwich-like perovskite solar cells (PSCs), the quality of perovskite layer is a challenge for further progress in PSCs due to the unfavorable defects and uncontrollable crystallization. Here, a surface post-treatment strategy employing ethyl thioglycolate (ET) as ligand molecule is developed for property manipulation of perovskite films. ET can lower surface energy of perovskite facets and induces secondary growth of grains, giving films with higher crystallinity and lower defect density. Meanwhile, both carbonyl and sulfhydryl in ET can bind to the Pb2+, thus forming bidentate anchoring on the surface for defect passivation. Besides, the perovskite/ET/C60 interface presents improved charge transfer owing to the well-aligned energy levels. Consequently, the power-conversion-efficiency (PCE) is boosted to 22.42% and 23.56% (certified 23.29%) for the FA0.85Cs0.15Pb(I0.95Br0.05)3 and FA0.9MA0.05Cs0.05Pb(I0.95Br0.05)3 PSCs, respectively, and the FA0.85Cs0.15Pb(I0.95Br0.05)3-based PSC with a larger area (1.03 cm2) delivers a PCE of 20.01%. Importantly, ET demonstrates effective management of I2 and PbI2, thereby preventing accelerated degradation and lead leakage of devices. Thanks to the multiple effects of ET, the resulting devices exhibit significantly enhanced ambient stability over a course of 800 h, and a thermal stability of over 1500 h while maintaining 80.4% of its original efficiency. The efficient and stable inverted perovskite solar cells are developed by introducing ethyl thioglycolate for synergistic crystallization modulation, surface passivation and interfacial PbI2/I2 management. image

  • 22.
    Wu, Bo
    et al.
    South China Normal Univ, Peoples R China; Nanyang Technol Univ, Singapore; Chinese Acad Sci, Peoples R China; Chinese Acad Sci, Peoples R China.
    Ning, Weihua
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Xu, Qiang
    Nanyang Technol Univ, Singapore.
    Manjappa, Manukumara
    Nanyang Technol Univ, Singapore.
    Feng, Minjun
    Nanyang Technol Univ, Singapore.
    Ye, Senyun
    Nanyang Technol Univ, Singapore.
    Fu, Jianhui
    Nanyang Technol Univ, Singapore.
    Lie, Stener
    Energy Res Inst NTU ERI N, Singapore.
    Yin, Tingting
    Nanyang Technol Univ, Singapore.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Goh, Teck Wee
    Nanyang Technol Univ, Singapore.
    Harikesh, Padinhare Cholakkal
    Energy Res Inst NTU ERI N, Singapore.
    Tay, Yong Kang Eugene
    Nanyang Technol Univ, Singapore.
    Shen, Ze Xiang
    Nanyang Technol Univ, Singapore; NTU Thales, Singapore.
    Huang, Fuqiang
    Chinese Acad Sci, Peoples R China.
    Singh, Ranjan
    Nanyang Technol Univ, Singapore.
    Zhou, Guofu
    South China Normal Univ, Peoples R China; Shenzhen Guohua Optoelect Technol Co Ltd, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Sum, Tze Chien
    Nanyang Technol Univ, Singapore.
    Strong self-trapping by deformation potential limits photovoltaic performance in bismuth double perovskite2021In: Science Advances, E-ISSN 2375-2548, Vol. 7, no 8, article id eabd3160Article in journal (Refereed)
    Abstract [en]

    Bismuth-based double perovskite Cs2AgBiBr6 is regarded as a potential candidate for low-toxicity, high-stability perovskite solar cells. However, its performance is far from satisfactory. Albeit being an indirect bandgap semiconductor, we observe bright emission with large bimolecular recombination coefficient (reaching 4.5 +/- 0.1 x 10(-11) cm(3) s(-1)) and low charge carrier mobility (around 0.05 cm(2) s(-1) V-1). Besides intermediate Frohlich couplings present in both Pb-based perovskites and Cs2AgBiBr6, we uncover evidence of strong deformation potential by acoustic phonons in the latter through transient reflection, time-resolved terahertz measurements, and density functional theory calculations. The Frohlich and deformation potentials synergistically lead to ultrafast self-trapping of free carriers forming polarons highly localized on a few units of the lattice within a few picoseconds, which also breaks down the electronic band picture, leading to efficient radiative recombination. The strong self-trapping in Cs2AgBiBr6 could impose intrinsic limitations for its application in photovoltaics.

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  • 23.
    Yan, Zhibo
    et al.
    Nanjing Univ, Peoples R China.
    Zhai, Wenjing
    Nanjing Univ, Peoples R China.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Li, Qian
    Nanjing Univ, Peoples R China.
    Lin, Lin
    Nanjing Univ, Peoples R China.
    Bao, Chunxiong
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zhang, Chunfeng
    Nanjing Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Liu, J-M
    Nanjing Univ, Peoples R China; South China Normal Univ, Peoples R China; South China Normal Univ, Peoples R China.
    Reversible Ionic Polarization in Metal Halide Perovskites2021In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 125, no 1, p. 283-289Article in journal (Refereed)
    Abstract [en]

    Metal halide perovskites have emerged as promising photovoltaic materials with attractive photoelectronic properties. However, the fundamental mechanisms for their outstanding properties are still elusive. In this work, we reveal the reversible bulk ionic polarization property of perovskites through studying the photoelectric response on the controllable states by electrical poling from room temperature to low temperature (200 K). The overall increase in light absorption, photoconductance, and carrier recombination lifetime demonstrates that the bulk ionic polarization contributes to the excellent photoelectric properties of halide perovskites. Moreover, we also discuss the role of ionic polarization in the overshoot transient photocurrent relaxation phenomenon after the electrical poling. This work would promote deep understanding in the unique properties of perovskites and their excellent photovoltaic performance.

  • 24.
    Zhang, Tiankai
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Kim, Hak-Beom
    Korea Inst Energy Res KIER, South Korea.
    Choi, In-Woo
    Korea Inst Energy Res KIER, South Korea.
    Wang, Chuan Fei
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Cho, Eunkyung
    Univ Arizona, AZ 85721 USA.
    Konefal, Rafal
    Czech Acad Sci, Czech Republic.
    Puttisong, Yuttapoom
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Terado, Kosuke
    Chiba Univ, Japan.
    Kobera, Libor
    Czech Acad Sci, Czech Republic.
    Chen, Mengyun
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Yang, Mei
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Bai, Sai
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Yang, Bowen
    Ecole Polytech Fed Lausanne, Switzerland; Uppsala Univ, Sweden.
    Suo, Jiajia
    Ecole Polytech Fed Lausanne, Switzerland; Uppsala Univ, Sweden.
    Yang, Shih-Chi
    Empa Swiss Fed Labs Mat Sci & Technol, Switzerland.
    Liu, Xianjie
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Fu, Fan
    Empa Swiss Fed Labs Mat Sci & Technol, Switzerland.
    Yoshida, Hiroyuki
    Chiba Univ, Japan; Chiba Univ, Japan.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Brus, Jiri
    Czech Acad Sci, Czech Republic.
    Coropceanu, Veaceslav
    Univ Arizona, AZ 85721 USA.
    Hagfeldt, Anders
    Ecole Polytech Fed Lausanne, Switzerland; Uppsala Univ, Sweden.
    Bredas, Jean-Luc
    Univ Arizona, AZ 85721 USA.
    Fahlman, Mats
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Kim, Dong Suk
    Korea Inst Energy Res KIER, South Korea.
    Hu, Zhang-Jun
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Ion-modulated radical doping of spiro-OMeTAD for more efficient and stable perovskite solar cells2022In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 377, no 6605, p. 495-501, article id eabo2757Article in journal (Refereed)
    Abstract [en]

    Record power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have been obtained with the organic hole transporter 2,2,7,7-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9-spirobifluorene (spiro-OMeTAD). Conventional doping of spiro-OMeTAD with hygroscopic lithium salts and volatile 4-tert-butylpyridine is a time-consuming process and also leads to poor device stability. We developed a new doping strategy for spiro-OMeTAD that avoids post-oxidation by using stable organic radicals as the dopant and ionic salts as the doping modulator (referred to as ion-modulated radical doping). We achieved PCEs of >25% and much-improved device stability under harsh conditions. The radicals provide hole polarons that instantly increase the conductivity and work function (WF), and ionic salts further modulate the WF by affecting the energetics of the hole polarons. This organic semiconductor doping strategy, which decouples conductivity and WF tunability, could inspire further optimization in other optoelectronic devices.

  • 25.
    Zhou, Yang
    et al.
    Ist Italiano Tecnol, Italy.
    van Laar, Simone C. W.
    Eindhoven Univ Technol, Netherlands.
    Meggiolaro, Daniele
    Ist CNR Sci & Tecnol Chim Giulio Natta CNR SCITEC, Italy.
    Gregori, Luca
    Ist CNR Sci & Tecnol Chim Giulio Natta CNR SCITEC, Italy; Univ Perugia, Italy; INSTM, Italy.
    Martani, Samuele
    Ist Italiano Tecnol, Italy.
    Heng, Jia-Yong
    Chinese Univ Hong Kong, Peoples R China.
    Datta, Kunal
    Molecular Materials and Nanosystems, Institute for Complex Molecular Systems, Eindhoven University of Technology, Eindhoven, The Netherlands.
    Jimenez-Lopez, Jesus
    Ist Italiano Tecnol, Italy.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Wong, E. Laine
    Ist Italiano Tecnol, Italy.
    Poli, Isabella
    Ist Italiano Tecnol, Italy.
    Treglia, Antonella
    Ist Italiano Tecnol, Italy.
    Cortecchia, Daniele
    Ist Italiano Tecnol, Italy.
    Prato, Mirko
    Ist Italiano Tecnol, Italy.
    Kobera, Libor
    Czech Acad Sci, Czech Republic.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zhao, Ni
    Chinese Univ Hong Kong, Peoples R China.
    Janssen, Rene A. J.
    Eindhoven Univ Technol, Netherlands.
    De Angelis, Filippo
    Ist CNR Sci & Tecnol Chim Giulio Natta CNR SCITEC, Italy; Univ Perugia, Italy; INSTM, Italy; Sungkyunkwan Univ, South Korea.
    Petrozza, Annamaria
    Ist Italiano Tecnol, Italy.
    How Photogenerated I<sub>2</sub> Induces I-Rich Phase Formation in Lead Mixed Halide Perovskites2023In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095Article in journal (Refereed)
    Abstract [en]

    Bandgap tunability of lead mixed halide perovskites (LMHPs) is a crucial characteristic for versatile optoelectronic applications. Nevertheless, LMHPs show the formation of iodide-rich (I-rich) phase under illumination, which destabilizes the semiconductor bandgap and impedes their exploitation. Here, it is shown that how I-2, photogenerated upon charge carrier trapping at iodine interstitials in LMHPs, can promote the formation of I-rich phase. I-2 can react with bromide (Br-) in the perovskite to form a trihalide ion I2Br- (I delta--I delta+-Br delta-), whose negatively charged iodide (I delta-) can further exchange with another lattice Br- to form the I-rich phase. Importantly, it is observed that the effectiveness of the process is dependent on the overall stability of the crystalline perovskite structure. Therefore, the bandgap instability in LMHPs is governed by two factors, i.e., the density of native defects leading to I-2 production and the Br- binding strength within the crystalline unit. Eventually, this study provides rules for the design of chemical composition in LMHPs to reach their full potential for optoelectronic devices.

  • 26.
    Zhou, Yang
    et al.
    Chinese University of Hong Kong, Peoples R China.
    Wang, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Cao, Yu
    Nanjing Technical University, Peoples R China.
    Wang, Jian-Pu
    Nanjing Technical University, Peoples R China.
    Fang, Hong-Hua
    Zernike Institute Adv Mat, Netherlands.
    Antonietta Loi, Maria
    Zernike Institute Adv Mat, Netherlands.
    Zhao, Ni
    Chinese University of Hong Kong, Peoples R China.
    Wong, Ching-Ping
    Chinese University of Hong Kong, Peoples R China.
    Benzylamine-Treated Wide-Bandgap Perovskite with High Thermal-Photostability and Photovoltaic Performance2017In: Advanced Energy Materials, ISSN 1614-6832, E-ISSN 1614-6840, Vol. 7, no 22, article id 1701048Article in journal (Refereed)
    Abstract [en]

    Mixed iodide-bromide organolead perovskites with a bandgap of 1.70-1.80 eV have great potential to boost the efficiency of current silicon solar cells by forming a perovskite-silicon tandem structure. Yet, the stability of the perovskites under various application conditions, and in particular combined light and heat stress, is not well studied. Here, FA(0.15)Cs(0.85)Pb(I0.73Br0.27)(3), with an optical bandgap of approximate to 1.72 eV, is used as a model system to investigate the thermal-photostability of wide-bandgap mixed halide perovskites. It is found that the concerted effect of heat and light can induce both phase segregation and decomposition in a pristine perovskite film. On the other hand, through a postdeposition film treatment with benzylamine (BA) molecules, the highly defective regions (e.g., film surface and grain boundaries) of the film can be well passivated, thus preventing the progression of decomposition or phase segregation in the film. Besides the stability improvement, the BA-modified perovskite solar cells also exhibit excellent photovoltaic performance, with the champion device reaching a power conversion efficiency of 18.1%, a stabilized power output efficiency of 17.1% and an open-circuit voltage (V-oc) of 1.24 V.

1 - 26 of 26
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