Exploring the synthesis, structure, and optoelectronic properties of lead-free halide perovskite Cs3Bi2I9 in single crystal and polycrystalline forms

Abstract In recent years, caesium bismuth iodide (Cs 3 Bi 2 I 9 ), a lead (Pb)-free halide perovskite, has drawn more attention as a potential material than traditional semiconductor materials due to its lack of Pb toxicity and its outstanding stability against atmospheric air and moisture. Herein, the inverse temperature crystallization method is adopted to grow high-quality hexagonal-phase Cs 3 Bi 2 I 9 perovskite single crystals. Furthermore, a Cs 3 Bi 2 I 9 perovskite thin film is fabricated by a solution process using the two-step spin coating technique. A collective analysis of the structural properties, surface morphology, thermal stability, phase transition, and optoelectronic properties of these single crystal and polycrystalline thin films provides a comprehensive understanding and design strategy to develop environmentally stable, Pb-free, and high-performance photovoltaic and optoelectronic devices based on Cs 3 Bi 2 I 9 perovskite. The findings of this study contribute to the advancement of perovskite-based technologies and pave the way for their successful integration into the renewable energy and optoelectronics industries.