Bowl‐Assisted Ball Assembly for Solvent‐Processing the C60 Electron Transport Layer of High‐Performance Inverted Perovskite Solar Cell

Abstract Pristine fullerene C 60 is an excellent electron transport material for state‐of‐the‐art inverted structure perovskite solar cells (PSCs), but its low solubility leaves thermal evaporation as the only method for depositing it into a high‐quality electron transport layer (ETL). To address this problem, we herein introduce a highly soluble bowl‐shaped additive, corannulene, to assist in C 60 ‐assembly into a smooth and compact film through the favorable bowl‐ball interaction. Our results show that not only corannulene can dramatically enhance the film formability of C 60 , it also plays a critical role in forming C 60 ‐corannulene (CC) supramolecular species and in boosting intermolecular electron transport dynamics in the ETL. This strategy has allowed CC devices to deliver high power conversion efficiencies up to 21.69 %, which is the highest value among the PSCs based on the solution‐processed‐C 60 (SP‐C 60 ) ETL. Moreover, the stability of the CC device is far superior to that of the C 60 ‐only device because corannulene can retard and curb the spontaneous aggregation of C 60 . This work establishes the bowl‐assisted ball assembly strategy for developing low‐cost and efficient SP‐C 60 ETLs with high promise for fully‐SP PSCs.