Transport Layer Engineering by Hydrochloric Acid for Efficient Perovskite Solar Cells with a High Open-Circuit Voltage.

A large number of defect states that exist at the interface between a perovskite film and an electron transport layer (ETL) are detrimental to the efficiency and the stability of perovskite solar cells (PSCs). It is still a challenge to simultaneously passivate the defects on both sides by a stable and low-cost ion compound. Herein, we demonstrate a simple and effective versatile strategy by introducing hydrochloric acid into SnO2 precursor solution to passivate the defects in both SnO2 and perovskite layers and simultaneously reduce the interface energy barrier, ultimately achieving a high-performance and hysteresis-free PSCs. Hydrogen ions can neutralize -OH groups on the SnO2 surface, whereas the Cl- can not only combine with Sn4+ in ETL but also suppress the Pb-I antisite defects formed at the buried interface. The reduced nonradiative recombination and the favorable energy level alignment result in a significantly increased efficiency from 20.71 to 22.06% of PSCs due to the enhancement of open-circuit voltage. In addition, the stability of the device can also be improved. This work presents a facile and promising approach for the development of highly efficient PSCs.