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

Abstract

Although SnO2 has been widely used as the electron transport material (ETM) of the perovskite solar cells (PSCs), the energy level mismatch at the SnO2/CsPbBr3 buried interface is as high as 1 eV, which is disastrous for the CsPbBr3‐based PSCs. Herein, a buffer layer of metal sulfide (CdS, ZnS) is introduced to solve this problem. The power conversion efficiency (PCE) of CsPbBr3 PSCs has been increased from 8.16% to 9.48% for ZnS‐treated SnO2 (ZnS‐SnO2), and a champion efficiency of 10.61% has been achieved in CdS‐treated SnO2 (CdS‐SnO2) devices. Aside from the reduced energy loss, the mobility of the SnO2 ETM has been greatly enhanced after the metal sulfide treatment. The CdS‐SnO2 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 CsPbBr3‐based PSCs reported to date. Finally, CdS‐SnO2 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 CsPbBr3 PSCs.