Direct Observation on p- to n-Type Transformation of Perovskite Surface Region during Defect Passivation Driving High Photovoltaic Efficiency

• Published in: Joule Vol. 5; no. 2; pp. 467 - 480
• Main Authors: Xiong, Shaobing, Hou, Zhangyu, Zou, Shijie, Lu, Xiaoshuang, Yang, Jianming, Hao, Tianyu, Zhou, Zihao, Xu, Jianhua, Zeng, Yihan, Xiao, Wei, Dong, Wei, Li, Danqin, Wang, Xiang, Hu, Zhigao, Sun, Lin, Wu, Yuning, Liu, Xianjie, Ding, Liming, Sun, Zhenrong, Fahlman, Mats, Bao, Qinye
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 17.02.2021
• Subjects: energetics; nonradiative recombination; p-n homojunction; passivation; perovskite solar cells; passivation; nonradiative recombination; p-n homojunction; energetics; perovskite solar cells
• ISSN: 2542-4351; 2542-4351
• DOI: 10.1016/j.joule.2020.12.009

Perovskite solar cells (PSCs) suffer from significant nonradiative recombination, limiting their power conversion efficiencies. Here, for the first time, we directly observe a complete transformation of perovskite MAPbI3 surface region energetics from p- to n-type during defect passivation caused by natural additive capsaicin, attributed to the spontaneous formation of a p-n homojunction in perovskite active layer. We demonstrate that the p-n homojunction locates at ∼100 nm below perovskite surface. The energetics transformation and defect passivation promote charge transport in bulk perovskite layer and at perovskite/PCBM interface, suppressing both defect-assisted recombination and interface carrier recombination. As a result, an efficiency of 21.88% and a fill factor of 83.81% with excellent device stability are achieved, both values are the highest records for polycrystalline MAPbI3 based p-i-n PSCs reported to date. The proposed new concept of synergetic defect passivation and energetic modification via additive provides a huge potential for further improvement of PSC performance. [Display omitted] •p- to n-type transformation of perovskite surface region during defect passivation•p-n homojunction locates at ∼100 nm below perovskite surface•New concept of synergetic defect passivation and energetics modification via additive•PCE up to record 21.88% for MAPbI3-based p-i-n PSCs Perovskite solar cells (PSCs) as one impressive next-generation photovoltaic technology have emerged due to their outstanding power conversion efficiency. Further PSC efficiency improvement is limited by significant nonradiative recombination loss due to defect states in perovskite layer and unmatched energetics at perovskite interface, which are creating a large gap to their full thermodynamic potential. Thus, electronically passivating perovskite bulk and interface defects as well as energetically modifying interfaces are highly critical issues to improve optoelectronic properties. Here, we observe a complete transformation from p- to n-type perovskite surface region energetics by a defect-passivating process via molecule additive, attributed to a spontaneous formation of p-n homojunction structure in perovskite active layer. The synergy between defect passivation and interface energetics-modification via additive significantly improves efficiency and stability of PSCs. We demonstrated a complete transformation of perovskite surface region energetics from p- to n-type during defect passivation via a nature molecule, capsaicin. We further observed the p-n homojunction locating at ∼100 nm below the perovskite surface. The synergies between defect passivation and energetics modification not only promoted charge transport but also suppressed the defect-assisted recombination and the interface carrier recombination in perovskite solar cells. We thus achieved a high efficiency of 21.88% and an impressive fill factor of 83.81% with an excellent device stability.