The three-dimensional-structure of twisted benzo[ghi]perylene-triimide dimer as a non-fullerene acceptor for inverted perovskite solar cells.

In this work, we introduced benzo[ghi]perylenetriimide (BPTI) derivatives including monomer and twisted dimer (t-BPTI) as an alternative electron transport layer (ETL) material to replace the commonly used PC61BM in inverted planar heterojunction perovskite solar cells. Moreover, the double ETL layer was applied in our perovskite solar cells with structure of glass/ITO/PEDOT:PSS/perovskite/BPTI/C60 or PDI-C4/BCP/Al. Use of a double ETL layer structure can effectively eliminate the leakage current. The devices with the t-BPTI/C60 double ETL layer yield an average power conversion efficiency of 10.73% and a maximum efficiency of 11.63%. The device based on the complete non-fullerene electron acceptors of t-BPTI/PDI-C4 as double ETL achieved maximum efficiency of 10.0%. Besides, it is found that the utilization of alloy t-BPTI+BPTI as ETL can effectively reduce the hysteresis effect of perovskite solar cells. The results suggest that BPTI based electron transport materials are potential alternatives for widely used fullerene acceptors in PSCs.