Enhancing open-circuit voltage in FAPbI3 perovskite solar cells via self-formation of coherent buried interface FAPbIxCl3−x

The interfaces between the perovskite and charge-transporting layers typically exhibit high defect concentrations, which are the primary cause of open-circuit voltage loss. Passivating the interface between the perovskite and electron-transporting layer is particularly challenging due to the dissolution of surface treatment agents during the perovskite coating. In this study, a coherent FAPbI_xCl_3-x buried interface was simultaneously formed during the preparation of FAPbI₃. This interlayer significantly improved charge extraction and transportation from the perovskite layer, while reducing trap state density. As a result, the open-circuit voltage increased from 1.01 V to 1.10 V, with the PCE improved from 19.05% to 22.89%.