RESUMO
Perovskite solar cells (PSCs) have attracted much attention at home and abroad due to their excellent photoelectric properties. Defects in the electron transport layer (ETL) and ETL/perovskite interface greatly affect the power conversion efficiency (PCE) and stability of PSCs. In the paper, the surface of tin dioxide (SnO2) ETL was modified by an alkali metal salt (NaBr, KBr, and RbBr) solution to optimize electron transport and passivate SnO2/perovskite. The results show that the photovoltaic performance of the PSCs is significantly improved after interfacial modification, especially the KBr-modified PSC has the highest PCE, which is 7.8% higher than that of the unmodified device, and the open-circuit voltage, short-circuit current density and fill factor are all greatly improved. This improvement is attributed to the fact that interfacial modification reduces the trap density of the SnO2 films, increases the mobility of the SnO2 films film, effectively passivates defects, and significantly inhibits the recombination at the SnO2/perovskite interface. This method aims to use simple and low-cost inorganic materials for effective interface modification.