Efficient small-molecule non-fullerene electron transporting materials for high-performance inverted perovskite solar cells

Two pi-conjugated small molecules based on the multifused rigid ladder-type backbone of ITCPTC are employed as the electron transporting materials in inverted perovskite solar cells. The two compounds are distinguished by the side chain thiophene and selenophene groups. Their energy levels match well with perovskite materials. Results demonstrate that the thiophene side chain endows ITCPTC-Th with smoother morphology, higher electron mobility, and more efficient electron extraction and electron transporting properties. Inverted PSCs with the ITCPTC-Th electron transporting material (ETL) show a high efficiency of 17.11%, which is higher than the efficiency of 16.12% obtained from the ITCPTC-Se-based PSCs. Notably, the performances of the ITCPTC-based ETLs are slightly higher than those of PCBM (with the highest PCE of 15.97%) under identical conditions. In addition, the two compounds also show excellent performance when applied as the interlayer between perovskite and the C-60 electron transporting layer. High efficiencies approaching 19% are obtained in devices containing the ITCPTC interlayers, further confirming their decent electron transporting properties. The ITCPTC compounds thus have great potential as efficient alternatives for the expensive PCBM ETL in inverted perovskite solar cells.