Indene-C-60 Bisadduct Electron-Transporting Material with the High LUMO Level Enhances Open-Circuit Voltage and Efficiency of Tin-Based Perovskite Solar Cells

Abstract

Tin-based halide perovskite materials are promising ecofriendly light absorbers with similar optoelectronic properties to lead-based ones. However, their solar cells have suffered from considerably low open-circuit voltage (V-OC) arising from mismatched energy levels between tin-based perovskite and charge-transporting layers because they imitate typical device structures developed for lead-based ones. Herein, we report that the lowest unoccupied molecular orbital (LUMO) level of the electron-transporting layer (ETL) significantly affects V-OC of tin-based perovskite solar cells (PSCs) in contrast to lead-based ones. The indene C-6(0) bisadduct ETL with a much higher LUMO level than that of typical ETLs decreases an energy off-set with the conduction band minimum of the mixed formamidinium/phenylethylammonium tin iodide (FA (0.9) PEA(0.1)Sn(1)( 3))-based perovskite material. The resultant reduced V-OC loss at their interface gives a V-OC of 0.651 V, the highest to date for FASnl(3)-based PSCs. The achieved champion power conversion efficiency reaches 7.05%. This result highlights the importance of redesigning device structures dedicated to tin-based PSCs.