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 incorporation graphene ink to 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 of PSCs based on 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 hours. Our results provide important insight for further efficiency boost in SnO2 based low-temperature processed PSCs.