Low-toxic metal halide perovskites: opportunities and future challenges

Over the past few years, lead halide perovskites have emerged as a class of dominant semiconductor materials in the photovoltaic (PV) field with an unprecedented sharp enhancement of power conversion efficiencies (PCEs) up to 22.1%, as well as in other promising optoelectronic applications due to their extraordinary and unique properties. However, the lead toxicity and long-term stability of these lead-based perovskites have raised considerable concerns for their real applications. Exploration of potentially low-toxic metal halide perovskite materials becomes one of the significant pivotal challenges in this century for PV, optoelectronic, and other unexplored applications. In this review, we summarize the recent progress on the development of low-toxic metal halide perovskites with a particular focus on their structures and properties, and discuss their potential applications in PV and optoelectronic devices. Moreover, we suggest current challenges and future research directions with the goal of stimulating further research interest and potential applications.