Multi‐Level Passivation of MAPbI<sub>3</sub> Perovskite for Efficient and Stable Photovoltaics
Ning Wei, Yuetian Chen, Xingtao Wang, Yanfeng Miao, Zhixiao Qin, Xiaomin Liu, Hao Wei, Yixin Zhao
Abstract
Abstract The photovoltaic performance and long‐term stability of perovskite solar cells (PSCs) are greatly affected by trap states. Herein, a functional ionic liquid of 1‐ethyl‐3‐methylimidazolium trifluoroacetate (EMIMTFA) is introduced, in which the 1‐ethyl‐3‐methylimidazolium cations (EMIM + ) can interact with PbI 2 to form a stable one‐dimensional (1D) perovskite of EMIMPbI 3 , and the trifluoroacetic acid anions (TFA − ) can passivate the interface between the electron transfer layer and the perovskite layer. Unlike, the widely studied low dimensional perovskite capping layers or quasi‐2D configuration, the EMIM + cations not only distribute on the top surface and inside the bulk phase, but also accumulate at the buried interface of 3D perovskite film, achieving a multi‐level distribution. The different defect states are successfully passivated by this distribution mode, leading to a significant decrease of non‐radiative recombination. As a result, the methyammonium lead iodide‐based PSCs with the EMIMTFA additive show an enhanced photovoltaic performance with a champion power conversion efficiency up to 22.14% and improved long‐term stability. This work demonstrates that the formation of multilevel low‐dimensional structure is a new strategy for the preparation of efficient and stable PSCs.