Low-temperature solution-processed SnO 2 electron transport layer modified by oxygen plasma for planar perovskite solar cells.

SnO 2 has attracted significant attention as an electron transport layer (ETL) because of its wide optical bandgap, electron mobility, and transparency. However, the annealing temperature of 180 °C-200 °C, as reported by several studies, for the fabrication of SnO 2 ETL limits its application for flexible devices. Herein, we demonstrated that the low-temperature deposition of SnO 2 ETL and further surface modification with oxygen plasma enhances its efficiency from 2.3% to 15.30%. Oxygen plasma treatment improves the wettability of the low-temperature processed SnO 2 ETL that results in a larger perovskite grain size. Hence, oxygen plasma treatment effectively improves the efficiency of perovskite solar cells at a low temperature and is compatible with flexible applications.