To achieve high photovoltaic performance of bulk hetero-junction organic solar cells(OSCs), a range of critical factors including absorption profiles, energy level alignment, charge carrier mobility and miscibility of...To achieve high photovoltaic performance of bulk hetero-junction organic solar cells(OSCs), a range of critical factors including absorption profiles, energy level alignment, charge carrier mobility and miscibility of donor and acceptor materials should be carefully considered. For electron-donating materials, the deep highest occupied molecular orbital(HOMO) energy level that is beneficial for high open-circuit voltage is much appreciated. However, a new issue in charge transfer emerges when matching such a donor with an acceptor that has a shallower HOMO energy level. More to this point, the chemical strategies used to enhance the absorption coefficient of acceptors may lead to increased molecular crystallinity, and thus result in less controllable phase-separation of photoactive layer. Therefore, to realize balanced photovoltaic parameters, the donor-acceptor combinations should simultaneously address the absorption spectra, energy levels, and film morphologies. Here, we selected two non-fullerene acceptors, namely BTPT-4F and BTPTT-4F, to match with a wide-bandgap polymer donor P2F-EHp consisting of an imidefunctionalized benzotriazole moiety, as these materials presented complementary absorption and well-matched energy levels. By delicately optimizing the blend film morphology, we demonstrated an unprecedented power conversion efficiency of over 16% for the device based on P2F-EHp:BTPTT-4F, suggesting the great promise of materials matching toward high-performance OSCs.展开更多
Revealing the charge generation is a crucial step to understand the organic photovoltaics. Recent development in non-fullerene organic solar cells （OSCs） indicates efficient charge separation even with negligible en...Revealing the charge generation is a crucial step to understand the organic photovoltaics. Recent development in non-fullerene organic solar cells （OSCs） indicates efficient charge separation even with negligible energetic offset between the donor and acceptor materials. These new findings trigger a critical question concerning the charge separation mechanism in OSCs, traditionally believed to result from sufficient energetic offset between the polymer donor and fullerene acceptor. We propose a new mechanism, which involves the molecular electrostatic potential, to explain efficient charge separation in non-fullerene OSCs. Together with the new mechanism, we demonstrate a record efficiency of -12% for systems with negligible energetic offset between donor and acceptor materials. Our analysis also rationalizes different requirement of the energetic offset between fullerene-based and non-fullerene OSCs, and paves the way for further design of OSC materials with both high photocurrent and high photovottage at the same time.展开更多
Methylammonium bismuth （III） iodide single crystals and films have been developed and investigated. We have further presented the first demonstration of using this organic-inorganic bismuth-based material to replace...Methylammonium bismuth （III） iodide single crystals and films have been developed and investigated. We have further presented the first demonstration of using this organic-inorganic bismuth-based material to replace lead/tin-based perovskite materials in solution-processable solar cells. The organic-inorganic bismuth-based material has advantages of non-toxicity, ambient stability, and low-temperature solution-processability, which provides a promising solution to address the toxicity and stability challenges in organolead- and organotin-based perovskite solar cells. We also demonstrated that trivalent metal cation-based organic-inorganic hybrid materials can exhibit photovoltaic effect, which may inspire more research work on developing and applying organic-inorganic hybrid materials beyond divalent metal cations （Pb （II） and Sn （II）） for solar energy applications.展开更多
有机太阳能电池(organic solar cell,OSC)是由有机材料构成活性层的太阳能电池.苯并[1,2-b:4,5-b']二噻吩(benzo[1,2-b:4,5-b']dithiophene,BDT)由于具有较大的刚性平面共轭结构,可以显著提高π电子的离域能力和分子间的π-π...有机太阳能电池(organic solar cell,OSC)是由有机材料构成活性层的太阳能电池.苯并[1,2-b:4,5-b']二噻吩(benzo[1,2-b:4,5-b']dithiophene,BDT)由于具有较大的刚性平面共轭结构,可以显著提高π电子的离域能力和分子间的π-π相互作用,且易化学修饰,合成方便,成为太阳能电池给体材料研究中的一个"明星分子"单元.目前,已报道的基于BDT共轭单元的有机光伏器件(organic photovoltaic device,OPV)的光电转化效率(power conversion efficiency,PCE)最高已达到9.95%,应用前景巨大.综述了BDT基小分子有机太阳能电池(small molecule organic solar cell,SM-OSC)活性层材料近年来的研究进展,并简要分析了小分子由于主链、侧链、封端基团的差异对器件性能的不同影响.展开更多
PEDOT:PSS buffer layers have been processed with the standard annealing step used for organic solar cells device applications. The d.c. conductivity σ as a function of temperature for two heating rates under He and a...PEDOT:PSS buffer layers have been processed with the standard annealing step used for organic solar cells device applications. The d.c. conductivity σ as a function of temperature for two heating rates under He and atmospheric air was studied. Moreover, the stability of the conductivity was investigated at different temperatures and environments vs time. The main results can be summarized in the following: the increase of σ due to the thermal activation of the carriers and the improvement of the crystallinity compete with the decrease of σ resulting from the irreversible structural degradation of the polymer chains promoted by the oxygen and moisture of the atmospheric air. The heat treatment time and the temperature at which the two competing mechanisms result in a maximum of the electrical conductivity have been determined and results are discussed relevant to organic optoelectronic devices containing PEDOT: PSS buffer layers.展开更多
基金supported by the National Natural Science Foundation of China (91633301, 51521002, 21822505, 21520102006)
文摘To achieve high photovoltaic performance of bulk hetero-junction organic solar cells(OSCs), a range of critical factors including absorption profiles, energy level alignment, charge carrier mobility and miscibility of donor and acceptor materials should be carefully considered. For electron-donating materials, the deep highest occupied molecular orbital(HOMO) energy level that is beneficial for high open-circuit voltage is much appreciated. However, a new issue in charge transfer emerges when matching such a donor with an acceptor that has a shallower HOMO energy level. More to this point, the chemical strategies used to enhance the absorption coefficient of acceptors may lead to increased molecular crystallinity, and thus result in less controllable phase-separation of photoactive layer. Therefore, to realize balanced photovoltaic parameters, the donor-acceptor combinations should simultaneously address the absorption spectra, energy levels, and film morphologies. Here, we selected two non-fullerene acceptors, namely BTPT-4F and BTPTT-4F, to match with a wide-bandgap polymer donor P2F-EHp consisting of an imidefunctionalized benzotriazole moiety, as these materials presented complementary absorption and well-matched energy levels. By delicately optimizing the blend film morphology, we demonstrated an unprecedented power conversion efficiency of over 16% for the device based on P2F-EHp:BTPTT-4F, suggesting the great promise of materials matching toward high-performance OSCs.
基金J. Hou acknowledge financial support from National Natural Science Foundation of China （91633301, 51673201, 91333204）, the Ministry of Science and Technology of China （2014CB643501） and the Chinese Academy of Sciences （XDB12030200）. F. Gao and D. Qian would like to acknowledge the Swedish Research Council VR （Grant No. 2017-007444 the Swedish Energy Agency Ener- gimyndigheten （2016-010174）, the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University （Faculty Grant No. SFO-Mat-LiU #2009- 00971）.
文摘Revealing the charge generation is a crucial step to understand the organic photovoltaics. Recent development in non-fullerene organic solar cells （OSCs） indicates efficient charge separation even with negligible energetic offset between the donor and acceptor materials. These new findings trigger a critical question concerning the charge separation mechanism in OSCs, traditionally believed to result from sufficient energetic offset between the polymer donor and fullerene acceptor. We propose a new mechanism, which involves the molecular electrostatic potential, to explain efficient charge separation in non-fullerene OSCs. Together with the new mechanism, we demonstrate a record efficiency of -12% for systems with negligible energetic offset between donor and acceptor materials. Our analysis also rationalizes different requirement of the energetic offset between fullerene-based and non-fullerene OSCs, and paves the way for further design of OSC materials with both high photocurrent and high photovottage at the same time.
文摘Methylammonium bismuth （III） iodide single crystals and films have been developed and investigated. We have further presented the first demonstration of using this organic-inorganic bismuth-based material to replace lead/tin-based perovskite materials in solution-processable solar cells. The organic-inorganic bismuth-based material has advantages of non-toxicity, ambient stability, and low-temperature solution-processability, which provides a promising solution to address the toxicity and stability challenges in organolead- and organotin-based perovskite solar cells. We also demonstrated that trivalent metal cation-based organic-inorganic hybrid materials can exhibit photovoltaic effect, which may inspire more research work on developing and applying organic-inorganic hybrid materials beyond divalent metal cations （Pb （II） and Sn （II）） for solar energy applications.
文摘PEDOT:PSS buffer layers have been processed with the standard annealing step used for organic solar cells device applications. The d.c. conductivity σ as a function of temperature for two heating rates under He and atmospheric air was studied. Moreover, the stability of the conductivity was investigated at different temperatures and environments vs time. The main results can be summarized in the following: the increase of σ due to the thermal activation of the carriers and the improvement of the crystallinity compete with the decrease of σ resulting from the irreversible structural degradation of the polymer chains promoted by the oxygen and moisture of the atmospheric air. The heat treatment time and the temperature at which the two competing mechanisms result in a maximum of the electrical conductivity have been determined and results are discussed relevant to organic optoelectronic devices containing PEDOT: PSS buffer layers.
