Organic ammonium chloride salt incorporated SnO2 electron transport layers for improving the performance of perovskite solar cells

The electron transport layer (ETL) is an integral part of perovskite solar cells (PSCs) to realize efficient carrier extraction and affect the growth of the upper perovskite layer in the n-i-p configuration. Adding substances is a common modification or engineering strategy to improve the quality of the solution processed SnO2 ETLs. Herein, a modification strategy of SnO2 ETLs by incorporating an organic ammonium chloride salt, propylammonium chloride (PACl), into the commercial SnO2 colloidal solution is presented. The corresponding engineering mechanisms including interaction between the organic salt and the alkaline colloidal solution and the following influences on the properties of the SnO2 layers, the ETL/perovskite interface, and the perovskite layers are investigated. A power conversion efficiency (PCE) of up to 22.27% is achieved in the n-i-p planar PSCs based on the PACl incorporated SnO2 ETLs. This work provides a reference for modification of the commercial SnO2 colloidal solution as well an understanding of the underlying mechanisms.