Modification of SnO₂ Electron Transport Layer in Perovskite Solar Cells

Rapid development of the device performance of organic-inorganic lead halide perovskite solar cells (PSCs) are emerging as a promising photovoltaic technology. Current world-record efficiency of PSCs is based on tin oxide (SnO₂) electron transport layers (ETLs), which are capable of being processed at low temperatures and possess high carrier mobilities with appropriate energy- band alignment and high optical transmittance. Modification of SnO₂ has been intensely investigated by various approaches to tailor its conductivity, band alignment, defects, morphology, and interface properties. This review article organizes recent developments of modifying SnO₂ ETLs to PSC advancement using surface and bulk modifications, while concentrating on photovoltaic (PV) device performance and long-term stability. Future outlooks for SnO₂ ETLs in PSC research and obstacles remaining for commercialization are also discussed.