Photovoltaic Performance of Vapor-Assisted Solution-Processed Layer Polymorph of Cs₃Sb₂I₉

The presence of toxic lead (Pb) remains a major obstruction to the commercial application of perovskite solar cells. Although antimony (Sb)-based perovskite-like structures A₃M₂X₉ can display potentially useful photovoltaic behavior, solution-processed Sb-based perovskite-like structures usually favor the dimer phase, which has poor photovoltaic properties. In this study, we prepared a layered polymorph of Cs₃Sb₂I₉ through solution-processing and studied its photovoltaic properties. The exciton binding energy and exciton lifetime of the layer-form Cs₃Sb₂I₉ were approximately 100 meV and 6 ns, respectively. The photovoltaic properties of the layered polymorph were superior to those of the dimer polymorph. A solar cell incorporating the layer-form Cs₃Sb₂I₉ exhibited an open-circuit voltage of 0.72 V and a power conversion efficiency of 1.5%-the highest reported for an all-inorganic Sb-based perovskite.