Multi‐Level Passivation of MAPbI3 Perovskite for Efficient and Stable Photovoltaics

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.