Multifunctional Organic Salt Regulated SnO2 Electron Transport Layer/Perovskite Interface for High Air‐Stable Perovskite Solar Cells

Abstract

Rationally adjusting the interface between SnO2 electron transport layer (ETL) and the perovskite (PVK) buried surface plays a key role in achieving efficient and stable PVK solar cells (PSCs). Herein, a cost‐effective organic salt, 5‐bromo‐6‐chloro‐3‐indolyl sulfate potassium salt (SPS), used as an interface modifier is deposited on the SnO2 ETL. SPS has played a multifunctional role in ETL and PVK layer: 1) the highly electronegative SO4− group of SPS can be adsorbed on the surface of SnO2 films, resulting in the energy levels of the PVK layer and SnO2 ETL becomes more compatible. 2) The lower contact angle of the modified SnO2 film is conducive to the formation of pinhole‐free PVK films. 3) The functional groups in SPS are helpful for the decrease of defect density in the PVK films. As a consequence, the defect density reduces from 8.17 × 1015 to 5.57 × 1015 cm−3. The power conversion efficiency (PCE) of modified PSCs increases from 19.82% to 21.33%. Furthermore, the unencapsulated modified devices retain 91.7% of the initial PCE after 624 h. These results indicate that using SPS as a multifunctional interface modifier is a promising strategy to achieve efficient and stable PSCs.