Solubilizing and stabilizing C60 with n-type polymer enables efficient inverted perovskite solar cells

Pristine fullerene C-60 is currently the best-performing electron transport layer (ETL) for perovskite solar cells (PSCs) but suffers from significant aggregation in solution. Consequently, the high-cost and complex thermal evaporation method is typically used to deposit high-quality C-60 ETLs. To address this challenge, we introduce an n-type polymeric additive that can solubilize and stabilize C-60 molecules for solution processing, leading to efficient and stable solution-processed-C-60 (SP-C-60) ETLs. The achievement is attributed to the well-matched properties of the n-type polymer and the precisely controlled intermolecular interactions between the polymer and C-60 . As a result, the SP-C-60 ETL with 5-wt % polymer addition afforded a champion power conversion efficiency of 25.60% (certified 25.09%). This is not only the highest performance among the current SP-C-60 devices but also highly competitive to the state-of-the-art thermally evaporated C-60 devices. Importantly, the champion device showed significantly enhanced stability (T95, light > 1,800 h; T80, heat = 700 h).