Strengthened Buried Interface via Metal Sulfide Passivation Toward High‐Performance CsPbBr3 Perovskite Solar Cells

Although SnO 2 has been widely used as the electron transport material (ETM) of the perovskite solar cells (PSCs), the energy level mismatch at the SnO 2 /CsPbBr 3 buried interface is as high as 1 eV, which is disastrous for the CsPbBr 3 ‐based PSCs. Herein, a buffer layer of metal sulfide (CdS, ZnS) is introduced to solve this problem. The power conversion efficiency (PCE) of CsPbBr 3 PSCs has been increased from 8.16% to 9.48% for ZnS‐treated SnO 2 (ZnS‐SnO 2 ), and a champion efficiency of 10.61% has been achieved in CdS‐treated SnO 2 (CdS‐SnO 2 ) devices. Aside from the reduced energy loss, the mobility of the SnO 2 ETM has been greatly enhanced after the metal sulfide treatment. The CdS‐SnO 2 devices also enjoy the benefits of reduced defect density and speeded carrier extraction, contributing to an almost 30% performance enhancement. This 10.61% PCE is among the highly efficient CsPbBr 3 ‐based PSCs reported to date. Finally, CdS‐SnO 2 devices survive a harsh damp heat test (120 °C with a relative humidity of 50%) for a month with less than 15% efficiency loss, demonstrating the superior stability of our CsPbBr 3 PSCs.