Research data supporting "Strongly Enhanced Photovoltaic Performance and Defect Physics of Air-Stable Bismuth Oxyiodide (BiOI)"

Abstract

Abstract for communication: Bismuth-based compounds have recently gained increasing attention as potentially non-toxic and defect-tolerant solar absorbers. However, many of the new materials recently investigated show limited photovoltaic performance. Herein, we explore in detail one such compound through theory and experiment: bismuth oxyiodide (BiOI). We grow BiOI thin films by chemical vapor transport and find them to maintain the same tetragonal phase in ambient air for at least 197 days. Our computations suggest BiOI to be tolerant to antisite and vacancy defects. We demonstrate an all-inorganic solar cell (ITO|NiOx|BiOI|ZnO|Al) with negligible hysteresis and up to 80% external quantum efficiency under select monochromatic excitation. The short-circuit current densities and power conversion efficiencies under AM 1.5G illumination are nearly double those of previously-reported BiOI solar cells, as well as other bismuth halide and chalcohalide photovoltaics recently explored by many groups. Through a detailed loss analysis using optical characterization, photoemission spectroscopy and device modeling, we provide direction for future improvements in efficiency. Our work demonstrates that BiOI, previously considered to be a poor photocatalyst, is promising for photovoltaics.