Photovoltaics of Low-Bandgap Inorganic Perovskites

Low-bandgap inorganic perovskites are a group of materials that can simultaneously benefit from the stability of an all-inorganic composition and high photovoltaic efficiency potential of low-bandgap light absorbers compared with other perovskite materials. Therefore, low-bandgap inorganic perovskites are promising materials for use in both single-junction and tandem solar cells. In this review, we summarize the recent studies focusing on the major issues related to these perovskites, including their low phase stability and uncontrolled Sn-related defects. We also present a prospective discussion regarding future research on these perovskites. First, we propose unraveling and harnessing the unique thermodynamic and kinetic behaviors of these perovskites to overcome their low phase stability. Second, we envision that fundamental studies leveraging 119Sn NMR may open new pathways for understanding and alleviating Sn-related defects. Efforts in these key areas are expected to unleash the full potential of low-bandgap inorganic perovskites for high-performance solar cells and modules.