Enhancing Efficiency and Stability of Inverted Perovskite Solar Cells through Solution-Processed and Structurally Ordered Fullerene

The electron transporting layer (ETL) used in high performance inverted perovskite solar cells (PSCs) is typically composed of C₆₀, which requires time-consuming and costly thermal evaporation deposition, posing a significant challenge for large-scale production. To address this challenge, herein, we present a novel design of solution-processible electron transporting material (ETM) by grafting a non-fullerene acceptor fragment onto C₆₀. The synthesized BTPC60 exhibits an exceptional solution processability and well-organized molecular stacking pattern, enabling the formation of uniform and structurally ordered film with high electron mobility. When applied as ETL in inverted PSCs, BTPC₆₀ not only exhibits excellent interfacial contact with the perovskite layer, resulting in enhanced electron extraction and transfer efficiency, but also effectively passivates the interfacial defects to suppress non-radiative recombination. Resultant BTPC₆₀-based inverted PSCs deliver an impressive power conversion efficiency (PCE) of 25.3% and retain almost 90% of the initial values after aging at 85°C for 1500 hours in N₂. More encouragingly, the solution-processed BTPC₆₀ ETL demonstrates remarkable film thickness tolerance, and enables a high PCE up to 24.8% with the ETL thickness of 200 nm. Our results highlight BTPC₆₀ as a promising solution-processed fullerene-based ETM, opening an avenue for improving the scalability of efficient and stable inverted PSCs.