Morphology control of SnO2 layer by solvent engineering for efficient perovskite solar cells

Abstract

Perovskite solar cells (PSCs) are considered among the most promising alternatives to Si-based solar cells, owing to the ongoing rise in their power conversion efficiencies (PCEs). While TiO2 has been widely used as an electron transport layer (ETL) in the n-i-p (regular) type PSCs, series of its disadvantages, including limited bulk electron mobility and photocatalytic character, restrict further improvement on the photovoltaic performance and environmental stability of devices. Therefore, SnO2 has attracted much attention as an alternative, because of its relatively low fabrication temperature, suitable energy alignment and high electron mobility. In this study, we effectively controlled the morphology of the SnO2 ETL by adding an organic solvent (ethanol) into the commercialized colloidal SnO2 precursor. This approach improved not only the wettability of the precursor on the glass substrate, but also the stability of the SnO2 colloidal dispersion. Thus, an aggregation-free SnO2 film with homogenous morphology was obtained with the assistance of ethanol, which also contributed to the improved crystal quality of the perovskite. The PSCs fabricated using ethanol-processed SnO2 exhibited a high PCE of 18.84% and improved environmental stability. Thus, our investigation provides a simple and effective approach toward achieving high-performance SnO2-based PSCs. © 2020 International Solar Energy Society