Small molecule-incorporated SnO2 layer for efficient perovskite solar cells

Abstract

Defect passivation with organic molecules is a significant strategy to improve perovskite solar cells (PSCs). However, because of carrier extraction and recombination in the bottom of the perovskite film, solar cell improvement is hindered. In this work, molecules of sodium 3-oxo-3H-spiro [isobenzofuran-1,9′-xanthene]-3′,6′-bis(olate) (SSB) were pre-buried into the SnO₂ electron transport layer (ETL), which resulted in modification of the SnO₂ and perovskite interface. This SSB molecular treatment improved the quality of the SnO₂ film. Moreover, the SSB molecule realized interfacial interaction with SnO₂ and perovskite, and substantially reduced the trap state density and enhanced charge extraction. As a result, the photovoltaic performances of the PSCs with the SSB devices improved, achieving an impressive efficiency of up to 22.64%. Additionally, the SSB devices without encapsulation demonstrated enhanced stability in air (at approximately 25 °C at approximately 30% humidity) and in an N₂ environment under continuous illumination.