Amino-capped zinc oxide modified tin oxide electron transport layer for efficient perovskite solar cells

Electron transport layer (ETL)/perovskite interface passivation is particularly challenging because of the use of polar solvents (e.g., DMF) for perovskite solution deposition, which usually destroy the bottom as-formed defect passivation layers. Herein, a novel multi-functional composite ETL, NH2-ZnO@SnO2, is prepared by mixing amino-capped ZnO (NH2-ZnO) nanocrystals (NCs) with SnO2 nanoparticles. The best-performing PSCs on the basis of NH2-ZnO@SnO2 achieve efficiency of 22.52%, which is significantly higher than that of the pristine SnO2 counterpart (18.45%) The enhanced performance of the NH2-ZnO@SnO2 ETL can be attributed to higher electron extraction capacity, better energy-level alignment with perovskite material, and more efficient carrier transport in device. Most important, the NH2 groups on the surface of ZnO NCs can effectively passivate the under-coordinated Pb2+ ions from perovskite films, thus reducing charge recombination at ETL/perovskite interface. The results suggest that NH2-ZnO NCs@SnO2 composite is a promising ETL for improving the performance of PSCs.