Controlled growth of uniform and dense perovskite layers on SnO2 via interface passivation by PbS quantum dots

Formamidinium lead iodide (FAPbI₃) and SnO₂ are a promising pair of halide perovskite and electron transport layer (ETL). However, FAPbI₃ and SnO₂ have inherent problems such as high crystallization temperature of FAPbI₃ and surface defects of SnO₂ like oxygen vacancies. They cause low crystallinity, non-uniform grain growth, and more interface defects, leading to carrier recombination and leakage current. The passivation of the interface between FAPbI₃ and SnO₂ is an effective process to address these materials issues. Herein, a dual role of lead sulfide (PbS) quantum dots (QDs) in the interface passivation is explored. PbS QDs which are introduced to the interface between FAPbI₃ and ETL, link to Sn-dangling bonds of SnO₂ ETLs and anchor the iodine atoms of FAPbI₃. This changes considerably lower nonradiative recombination, achieve a better energetic alignment between ETL and PbI₃, and facilitate electron extraction, leading to a power conversion efficiency of 21.66%.