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 C, 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 C. The synthesized BTPC 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, BTPC 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 BTPC-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 N. More encouragingly, the solution-processed BTPC 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 BTPC as a promising solution-processed fullerene-based ETM, opening an avenue for improving the scalability of efficient and stable inverted PSCs.