Electron transport layer assisted by nickel chloride hexahydrate for open-circuit voltage improvement in MAPbI 3 perovskite solar cells.

SnO 2 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 2 and the perovskite layer necessitates further exploration. Nickel chloride hexahydrate (NiCl 2 ·6H 2 O) was introduced into the SnO 2 ETL, which significantly increased the power conversion efficiency (PCE) from 15.49 to 17.36% and the open-circuit voltage ( V OC ) from 1.078 to 1.104 V. The improved PCE and V OC were attributed to the reduced defect states and increased energy level of the conduction band minimum. This work provides new insights into optimizing the V OC and PCE of PSCs.