Modulation of Electron Transport Layers To Minimize Voltage Loss in CsSnI 3 Perovskite Solar Cells

The efficiency of tin-based perovskite solar cells, particularly the inorganic CsSnI 3, remains far below that of lead-based counterparts due to the substantial voltage loss at the charge transport layer-perovskite interface. Systematic research shows that the voltage loss in the CsSnI 3 perovskite planar solar cells is mainly due to the reduction in the splitting of the quasi-Fermi energy level and the increase in the energy band bending at the electron transport layer (ETL)-perovskite interface. In this study, we propose the fullerene derivative tetramethylcyclobutadiene-C 60 (TMCB), which has the high lowest unoccupied molecular orbital energy level, as an ETL for CsSnI 3 perovskite planar solar cells to minimize voltage losses. The TMCB ETL has been demonstrated to facilitate CsSnI 3 -based perovskite solar cells to achieve a remarkable power conversion efficiency of 14.95% with a high open circuit voltage of 0.81 V measured under AM 1.5G irradiation.