A critical review on Bismuth and Antimony halides based perovskites and derivatives for photovoltaic applications: recent advances and challenges

For the past decade, lead halide perovskites have experienced impressive progress in photovoltaics with the certified device conversion efficiency over 25%, owing to their outstanding optoelectronic properties. However, the toxicity and environmental instability of the core lead halides materials would strongly limit their commercialization. Within this scenario, research investigations directed at assessing properties and opportunities offered by emerging lead-free halide perovskites are becoming everyday more relevant to pinpoint new low-cost/low-toxicity solutions for solar-to-electricity conversion. In this review, Group VA metals, namely Bismuth (Bi) and Antimony (Sb) halide based perovskites and derivatives with different valence states are classified based on formulas of A3B2X9, A2AgBX6, also known as double perovskites, and AgaBibXa+3b, called Rudorffites (A = MA, Cs, Rb, etc.; B = Bi, Sb; X = I, Br, Cl). Here, we summarize the recent progresses in exploitation of these materials, with a special attention devoted to the description of the crystal structures, the thin film preparation methods and the performances in real device, including both theoretical insights and experimental observations. With this survey, we are able to provide reasonable perspectives for the future development of high-performance photovoltaic devices based on lead-free bismuth/antimony halide based perovskite and derivatives.