Efficient and air-stable perovskite solar cells driven by interfacial self-assembly and hydrogen bond system: Dual interface passivation and collaborative mechanism

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) based on SnO 2 electron transport layer (ETL) has exceeded 26.1 %. However, defects located at interfaces of ETL/perovskite films and perovskite/hole transport layer (HTL) remain a key factor in reducing performance of PSCs, especially in the air environment. The effect of single defect passivation of SnO 2 ETL/perovskite or perovskite films/HTL on performance of PSCs is limited. In addition, the green and stable characteristics of passivation agents are important factors that must be considered for the sustainable development of perovskite solar cells. To address this, natural amphiphilic betaine molecules and green hydrogen bond system composed of imidazole and salicylic acid (ImA-SA HBS) are introduced, which simultaneously passivate SnO 2 ETL/perovskite and perovskite/HTL defects. The addition of betaine not only improves the charge extraction at the SnO 2 /perovskite interface, but also suppresses the recombination of photogenerated carriers. Furthermore, due to introduction of ImA-SA HBS, the charge transport between perovskite grains and energy level matching of perovskite/HTL interface are improved, which increase the PCE of PSCs prepared in air from 20.67 % to 22.20 %. Furthermore, the PSCs passivated with betaine and HBS show no decrease in PCE after being stored in air for 66 days. This paper provides theoretical basis and technical support for defect passivation strategy and performance optimization of PSCs prepared in air environment.