Solvent-assisted preparation of low-temperature SnO2 electron transport layers for efficient and stable perovskite solar cells made in ambient conditions

Abstract

In terms of high electron mobility and good stability, the SnO₂ based electron transport layer (ETL) is favored by uncountable researchers. However, how to reduce the surface defects and improve the crystalline quality of the SnO₂ ETL during low-temperature preparation is still a great challenge. Here, we develop a brief solvothermal synthesis method to prepare a SnO₂ ETL with high quality at a low temperature, in which a mixed solution of ethanol and water is chosen as the solvent to enhance the crystallinity of SnO₂. Notably, the preparation of the SnO₂ ETL only requires annealing at 85 °C, which efficiently promotes process simplification and cost savings. Based on the fluorine-doped tin oxide (FTO)/SnO₂/perovskite/Spiro-OMeTAD/Au structure, the champion device has a power conversion efficiency (PCE) of up to 19.21% with low hysteresis. The unencapsulated device can maintain more than 93% of its original efficiency after 1440 h in an atmospheric environment, and its initial efficiency is only reduced by about 9% after heating at 85 °C for 24 h, showing good long-term stability and good thermal stability. Importantly, the assembly and testing of the devices are done in an atmospheric environment, which provides a new route to the preparation of high-performance SnO₂-based perovskite solar cells (PSCs) in the air.