Research Update: Bismuth based materials for photovoltaics

In this Research Update, we briefly summarize some of the bismuth materials that have been investigated for their use in photovoltaic solar cells. We focus on bismuth-based perovskites and bismuth halides, as alternatives to lead-halide perovskites, and bismuth-based sulfides (Bi2S3, CuxBiySz, and AgBiS2), as alternatives to lead sulfide quantum dots. These materials fulfill the requirements of being composed of abundant and non-toxic elements. Moreover, they exhibit adequate properties for photovoltaics like high absorption coefficients and suitable bandgaps, plus additional attractive characteristics in terms of robustness and stability. However, they have not been extensively studied and therefore their efficiencies are still far from those reported for their toxic counterparts. Here we collect some of the most promising results, point at possible limiting factors, and suggest some routes to improve performance. (C) 2018 Author(s)