Cesium-Trifluoroacetate Doped MA/FA-Based Perovskite Solar Cells with Inverted Planar Structure

Triple cation perovskites are of particular interest among halide perovskites due to their impressive photovoltaic performance. In this paper, we introduce cesium trifluoroacetate (CsTFA) into methylammonium/formamidinium (MA/FA) perovskite to prepare a triple cation Cs/MA/FA perovskite solar cell with inverted planar structure. The effects of CsTFA concentration and spinning speed of the perovskite layer on the morphology of perovskite film and performance of the perovskite solar cell are studied. We find that the power conversion efficiency can be 10.55% when the spinning speed is 6000 rpm and CsTFA content is 5%. When, ethylammonium chlorine (MACl) is then employed to passivate the Cs/MA/FA-based perovskite thin film surface, the power conversion efficiency (PCE) is further improved to 12.19%. The results indicate that CsTFA can be a potential source of Cs ions for triple cation Cs/MA/FA perovskite solar cells.