Department of Chemistry and Centre for Plastic Electronics, Imperial College London, London, SW7 2AZ, UK.
Department of Physics and Centre for Plastic Electronics, Imperial College London, London, SW7 2AZ, UK.
Adv Mater. 2017 Sep;29(33). doi: 10.1002/adma.201701156. Epub 2017 Jun 28.
A comparison of the efficiency, stability, and photophysics of organic solar cells employing poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3'″-di(2-octyldodecyl)-2,2';5',2″;5″,2'″-quaterthiophen-5,5'″-diyl)] (PffBT4T-2OD) as a donor polymer blended with either the nonfullerene acceptor EH-IDTBR or the fullerene derivative, [6,6]-phenyl C butyric acid methyl ester (PC BM) as electron acceptors is reported. Inverted PffBT4T-2OD:EH-IDTBR blend solar cell fabricated without any processing additive achieves power conversion efficiencies (PCEs) of 9.5 ± 0.2%. The devices exhibit a high open circuit voltage of 1.08 ± 0.01 V, attributed to the high lowest unoccupied molecular orbital (LUMO) level of EH-IDTBR. Photoluminescence quenching and transient absorption data are employed to elucidate the ultrafast kinetics and efficiencies of charge separation in both blends, with PffBT4T-2OD exciton diffusion kinetics within polymer domains, and geminate recombination losses following exciton separation being identified as key factors determining the efficiency of photocurrent generation. Remarkably, while encapsulated PffBT4T-2OD:PC BM solar cells show significant efficiency loss under simulated solar irradiation ("burn in" degradation) due to the trap-assisted recombination through increased photoinduced trap states, PffBT4T-2OD:EH-IDTBR solar cell shows negligible burn in efficiency loss. Furthermore, PffBT4T-2OD:EH-IDTBR solar cells are found to be substantially more stable under 85 °C thermal stress than PffBT4T-2OD:PC BM devices.
报告了将聚[(5,6-二氟-2,1,3-苯并噻二唑-4,7-二基)-交替-(3,3'′-二(2-辛基十二烷基)-2,2';5',2″;5″,2'″-四噻吩-5,5'″-二基)] (PffBT4T-2OD) 作为给体聚合物与非富勒烯受体 EH-IDTBR 或富勒烯衍生物[6,6]-苯基 C 丁酸甲酯 (PC BM) 混合的有机太阳能电池的效率、稳定性和光物理性能的比较。未添加任何加工添加剂的倒置 PffBT4T-2OD:EH-IDTBR 共混太阳能电池的功率转换效率 (PCE) 达到 9.5 ± 0.2%。这些器件表现出 1.08 ± 0.01 V 的高开路电压，这归因于 EH-IDTBR 的高最低未占据分子轨道 (LUMO) 能级。荧光猝灭和瞬态吸收数据用于阐明两种共混物中电荷分离的超快动力学和效率，其中 PffBT4T-2OD 激子在聚合物域内的扩散动力学以及激子分离后的复合损失被确定为决定光电流产生效率的关键因素。值得注意的是，虽然封装的 PffBT4T-2OD:PC BM 太阳能电池在模拟太阳照射下表现出显著的效率损失（“燃烧”退化），因为通过增加光致陷阱状态的陷阱辅助复合，但 PffBT4T-2OD:EH-IDTBR 太阳能电池的“燃烧”效率损失可以忽略不计。此外，与 PffBT4T-2OD:PC BM 器件相比，PffBT4T-2OD:EH-IDTBR 太阳能电池在 85°C 热应力下的稳定性显著提高。
