Interfacial Molecular Doping of Metal Halide Perovskites for Highly Efficient Solar Cells

• Published in: Advanced materials (Weinheim) Vol. 32; no. 31; pp. e2001581 - n/a
• Main Authors: Jiang, Qi, Ni, Zhenyi, Xu, Guiying, Lin, Yun, Rudd, Peter N., Xue, Rongming, Li, Yaowen, Li, Yongfang, Gao, Yongli, Huang, Jinsong
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.08.2020
• Subjects: Aniline; Carrier density; Charge transfer; Doping; Electrons; Heterojunctions; interfacial molecular doping; Materials science; Metal halides; perovskite solar cells; Perovskites; Photoelectric effect; Photoelectric emission; Photovoltaic cells; Solar cells; Stability
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202001581

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 FAxMA1−xPbI3 (FA: HC(NH2)2; MA: CH3NH3) 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. A small molecule of 4,4′,4″,4′″‐(pyrazine‐2,3,5,6‐tetrayl) tetrakis (N,N‐bis(4‐methoxyphenyl) aniline) (PT‐TPA) is applied to effectively p‐dope the FAxMA1−xPbI3 (FA:HC(NH2)2; MA:CH3NH3) perovskite surface, with obvious conductivity and carrier concentration increase. After applying PT‐TPA into perovskite solar cells, the doping‐induced band bending at the perovskite surface facilitates hole extraction to the hole‐transport layer and expels electrons toward the cathode, which reduces surface charge recombination. The optimized devices demonstrate a stabilized efficiency of 22.9%.