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.
Keywords: charge recombination; graphene ink; low-temperature process; stability; trap state.