Acenaphthylene-imide based small molecules/TiO ₂ bilayer as electron-transporting layer for solution-processing efficient perovskite solar cells

It is of great significance to design and synthesize highly efficient n-type organic small molecules as electron-transporting layer (ETL) materials to achieve high performance planar perovskite solar cells (PVKSCs) with low-temperature solution-processing. In this article, acenaphthylene-imide based small molecules AI1, AI2 and AI3 were developed with lower-lying LUMO energy levels and were further applied as non-fullerene ETL materials for solution-processed PVKSCs. When TiO ₂ /AIX bilayer was used as ETL, an average power conversion efficiency (PCE) of 15.0% was achieved for TiO ₂ /AI1 based PVKSCs with conventional configuration, while pristine TiO ₂ based devices presented a PCE of 11.7% only. All the results demonstrate that acenaphthylene-imide derivatives could be promising ETL materials to accomplish low-temperature solution-processed high performance PVKSCs.