Surface Dedoping for Methylammonium-Free Tin–Lead Perovskite Solar Cells

For Sn–Pb-based perovskite solar cells (PSCs), surface p-doping-related defects including Sn vacancies, FA vacancies, and I-related defects substantially impact the local work function and band structure, thus resulting in inefficient carrier transfer kinetics at the perovskite/C60 interface. Herein, a surface dedoping strategy is rationally designed based on synergistic passivation of p-doping-related defects, in which shallow-level defects are compensated and localized electronic states caused by deep-level defects are removed. Accordingly, the back surface electrical-field by a concomitantly formed n/n+ homojunction as well as reduced surface potential fluctuations minimize the electron extraction barrier. The electron mobility and built-in voltage are greatly enhanced, and carrier lifetimes are elongated to over 7 μs. Meanwhile, the cooperative stabilization of surface components suppresses I– ion migration and Sn2+ oxidation. The resulting MA-free Sn–Pb PSCs deliver a champion efficiency of 22.05%, along with maintaining 94% of the initial efficiency after 1200 h of aging in N2.