Jiang Qi, Ni Zhenyi, Xu Guiying, Lin Yun, Rudd Peter N, Xue Rongming, Li Yaowen, Li Yongfang, Gao Yongli, Huang Jinsong
Department of Applied Physical Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.
Laboratory of Advanced Optoelectronic Materials, College of Chemistry Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, China.
Adv Mater. 2020 Aug;32(31):e2001581. doi: 10.1002/adma.202001581. Epub 2020 Jun 25.
Tailoring the doping of semiconductors in heterojunction solar cells shows tremendous success in enhancing the performance of many types of inorganic solar cells, while it is found challenging in perovskite solar cells because of the difficulty in doping perovskites in a controllable way. Here, a small molecule of 4,4',4″,4″'-(pyrazine-2,3,5,6-tetrayl) tetrakis (N,N-bis(4-methoxyphenyl) aniline) (PT-TPA) which can effectively p-dope the surface of FA MA PbI (FA: HC(NH ) ; MA: CH NH ) perovskite films is reported. The intermolecular charge transfer property of PT-TPA forms a stabilized resonance structure to accept electrons from perovskites. The doping effect increases perovskite dark conductivity and carrier concentration by up to 4737 times. Computation shows that electrons in the first two layers of octahedral cages in perovskites are transferred to PT-TPA. After applying PT-TPA into perovskite solar cells, the doping-induced band bending in perovskite effectively facilitates hole extraction to hole transport layer and expels electrons toward cathode side, which reduces the charge recombination there. The optimized devices demonstrate an increased photovoltage from 1.12 to 1.17 V and an efficiency of 23.4% from photocurrent scanning with a stabilized efficiency of 22.9%. The findings demonstrate that molecular doping is an effective route to control the interfacial charge recombination in perovskite solar cells which is in complimentary to broadly applied defect passivation techniques.
在异质结太阳能电池中对半导体进行掺杂调控，在提升多种无机太阳能电池性能方面取得了巨大成功，然而在钙钛矿太阳能电池中却颇具挑战，因为难以以可控方式对钙钛矿进行掺杂。在此，报道了一种小分子4,4',4″,4″'-(吡嗪-2,3,5,6-四亚基)四( N,N-双(4-甲氧基苯基)苯胺)(PT-TPA)，它能够有效地对FA MA PbI（FA: HC(NH ) ; MA: CH NH ）钙钛矿薄膜表面进行p型掺杂。PT-TPA的分子间电荷转移特性形成了稳定的共振结构以接受来自钙钛矿的电子。这种掺杂效应使钙钛矿暗电导率和载流子浓度提高了多达4737倍。计算表明，钙钛矿八面体笼前两层中的电子转移到了PT-TPA。将PT-TPA应用于钙钛矿太阳能电池后，钙钛矿中掺杂诱导的能带弯曲有效地促进了空穴向空穴传输层的提取，并将电子驱向阴极侧，从而减少了那里的电荷复合。优化后的器件光电压从1.12 V提高到1.17 V，光电流扫描效率为23.4%，稳定效率为22.9%。这些发现表明，分子掺杂是控制钙钛矿太阳能电池界面电荷复合的有效途径，这与广泛应用的缺陷钝化技术相辅相成。
