Recent Advances in Bismuth‐Based Solar Cells: Fundamentals, Fabrication, and Optimization Strategies

Abstract Solar cells are star technologies in the utilization of renewable energy and have experienced tremendous development in the past few decades. Eco‐friendly processing technologies and materials to reduce the negative impacts and extend the lifetime of photovoltaics are becoming a very attractive research area. Bismuth triiodide, with its appropriate structure and suitable optoelectronic properties, has proved to be a low‐toxic and stable material for optoelectronic devices, and the best‐reported power conversion efficiencies (PCEs) are 1.50% for solar cells with BiI₃ as photoactive layers and 5.56% for BiI₃ based perovskite solar cells. Further developments in film fabrication and morphological control are necessary to improve the PCEs of bismuth‐based solar cells. In this review, the electronic structures and optical properties of bismuth halides materials are introduced to reveal their potential in solar cells. Then, different fabrication techniques including solvent engineering, solvent annealing, thermal engineering, and vapor phase fabrication are discussed. More importantly, the absorber layer optimization strategies and the interface engineering are summarized to improve performance of BiI₃ solar cells. In the end, the challenges of BiI₃ based solar cells and future research directions are discussed.