Enhanced stability and efficiency in hole-transport-layer-free CsSnI3 perovskite photovoltaics

Photovoltaics based on tin halide perovskites have not yet benefited from the same intensive research effort that has propelled lead perovskite photovoltaics to >20% power conversion efficiency, due to the susceptibility of tin perovskites to oxidation, the low energy of defect formation and the diffcultly in forming pinhole-free films. Here we report CsSnI3 perovskite photovoltaic devices without a hole-selective interfacial layer that exhibit a stability similar to 10 times greater than devices with the same architecture using methylammonium lead iodide perovskite, and the highest efficiency to date for a CsSnI3 photovoltaic: 3.56%. The latter largely results from a high device fill factor, achieved using a strategy that removes the need for an electron-blocking layer or an additional processing step to minimize the pinhole density in the perovskite film, based on co-depositing the perovskite precursors with SnCl2. These two findings raise the prospect that this class of lead-free perovskite photovoltaic may yet prove viable for applications.