Inorganic and Pb-Free CsBi₃I₁₀ Thin Film for Photovoltaic Applications

Computational, thin-film deposition, and characterization approaches have been used to investigate the all-inorganic lead-free CsBi₃I₁₀ as a candidate to act as a thin-film photovoltaic absorber. In this paper, CsBi₃I₁₀ was firstly predicted with a layer crystal structure of stable hexagonal phase-like Cs₃Bi₂I₉ and then prepared by one-step coating also showing the high purity hexagonal phase and crystallinity, very consistent with the theoretical calculation. After solvent annealing, a high absorption coefficient of approximately 10⁵ cm^–1 in visible light and a suitable optical band gap of 1.78 eV were obtained for the CsBi₃I₁₀ thin film. The solar cell based on the CsBi₃I₁₀ perovskite thin film exhibited a high power conversion efficiency of 1.05%, good reproducibility, hysteresis-free behavior, and long-term stability. These results indicate that the performance of all-inorganic Pb-free perovskite solar cells can be further improved.