Electron transport layer assisted by nickel chloride hexahydrate for open-circuit voltage improvement in MAPbI perovskite solar cells.

SnO is a promising electron transport layer (ETL) material with important applications in planar perovskite solar cells (PSCs). However, electron-hole recombination and charge extraction between SnO and the perovskite layer necessitates further exploration. Nickel chloride hexahydrate (NiCl·6HO) was introduced into the SnO ETL, which significantly increased the power conversion efficiency (PCE) from 15.49 to 17.36% and the open-circuit voltage ( ) from 1.078 to 1.104 V. The improved PCE and were attributed to the reduced defect states and increased energy level of the conduction band minimum. This work provides new insights into optimizing the and PCE of PSCs.