Hysteresis-free perovskite solar cells with over 24% efficiency enabled by ZnCl₂ doped SnO₂ electron transfer layer

Tin dioxide (SnO2) has been widely applied as the electron transport layer (ETL) in perovskite solar cells. However, the SnO2 with low conduction band minimum that has mismatched energy levels between the perovskite film and severe SnO2/perovskite interfacial defects is liable to cause nonradiative recombination. In order to modify the SnO2 layer, herein, we introduced the zinc chloride (ZnCl2) hydrochloric acid solution into the SnO2 nanocrystals solution (SnO2-Zn) and proved that ZnCl2 doping in the SnO2 ETL is a simple and low-cost passivation method, which can significantly improve the efficiency and stability of devices and remove the hysteresis. Ultimately, an enhancement of open-circuit voltage from 1.13 to 1.16 V and an increased corresponding power conversion efficiency from 22.88% to 24.12% are achieved for the devices using SnO2-Zn ETL.