Graphene-Modified Tin Dioxide for Efficient Planar Perovskite Solar Cells with Enhanced Electron Extraction and Reduced Hysteresis

Tin dioxide (SnO2) as an efficient electron transport layer (ETL) has been demonstrated for emerging high-performance organic-inorganic hybrid perovskite solar cells (PSCs). However, the low-temperature solution-processed SnO2 usually results in high trap-state density and current-voltage hysteresis. Here, we reported an effective strategy to solve this problem by incorporating graphene ink into the low-temperature processed SnO2 for planar structure PSCs. The electron extraction efficiency has been significantly improved with graphene-doped SnO2 ETL coupled with attenuated charge recombination at the ETL/perovskite interface. The power conversion efficiency (PCE) of PSCs based on the graphene-SnO2 ETL reached over 18% with negligible hysteresis. Incorporation of graphene into the ETL layer also enhanced the device stability retaining 90% of the initial PCE value after storing in ambient condition with a relative humidity of 40 +/- 5% for 300 h. Our results provide an important insight into further efficiency boost in SnO2-based low-temperature processed PSCs.