Cs₃Bi₂I₉ has been proposed to be an alternate candidate for various optoelectronic applications to meet the stability and toxicity issues associated with the highly performing organic lead halide perovskites. In the present work, we report the in situ formation of cesium bismuth iodide thin films by ultrasonically assisted sequential spray deposition of BiI₃ and CsI in ethanol-based precursor solutions. The films formed by varying the layer configurations and relative molarity were investigated to identify the optimum conditions to obtain pure Cs₃Bi₂I₉ films. Further, we probe their structure, morphology, optical and electronic properties in combination with computational studies. X-ray diffraction and Raman spectroscopy confirmed the crystallinity and chemical structure of the spray cast perovskite films. Scanning electron microscopy images present the surface morphology composed of uniformly distributed hexagonal grains of ∼ 280 nm in average size. The absorption coefficient of the films was evaluated in the order of ~ 10⁶ cm⁻¹ using UV–Vis–NIR spectral analysis. The calculated direct band gap value of 1.99 eV was in accordance with the theoretical calculations. Furthermore, the optimized Cs₃Bi₂I₉ film was photoconductive. The I-V characteristics of FTO/ZnO/Cs₃Bi₂I₉/C-Ag heterojunction revealed a significant rectification behavior with a diode factor of 1.75. FTO/CdS/Cs₃Bi₂I₉/C-Ag heterojunction showed a V_oc of 300 mV and Jsc of 0.003 mA cm⁻². Our results imply that the spray deposited Cs₃Bi₂I₉ films have a profound potential for applications in photodetectors and solar cells upon detailed investigations.

Cs ₃ Bi ₂ I ₉已被提议作为各种光电应用的替代候选物，以满足与高性能有机卤化铅钙钛矿相关的稳定性和毒性问题。在目前的工作中，我们报告了在乙醇基前体溶液中通过超声辅助顺序喷雾沉积 BiI ₃和 CsI原位形成碘化铯铋薄膜。研究了通过改变层配置和相对摩尔浓度形成的薄膜，以确定获得纯 Cs ₃ Bi ₂ I ₉的最佳条件电影。此外，我们结合计算研究探索了它们的结构、形态、光学和电子特性。X 射线衍射和拉曼光谱证实了喷铸钙钛矿薄膜的结晶度和化学结构。扫描电子显微镜图像显示了由平均尺寸约 280 nm 的均匀分布的六边形晶粒组成的表面形态。使用UV-Vis-NIR光谱分析以~10 ⁶ cm ^-1的数量级评估薄膜的吸收系数。计算出的直接带隙值为 1.99 eV，与理论计算一致。此外，优化的 Cs ₃ Bi ₂ I ₉薄膜是光电导的。FTO/ZnO/Cs ₃ Bi ₂ I ₉ /C-Ag 异质结的IV 特性显示出显着的整流行为，二极管系数为1.75。FTO/CdS/Cs ₃ Bi ₂ I ₉ /C-Ag异质结显示出300 mV的V _oc和0.003 mA cm ^{-2 的}Jsc 。我们的结果表明，经过详细研究，喷雾沉积的 Cs ₃ Bi ₂ I ₉薄膜在光电探测器和太阳能电池中具有巨大的应用潜力。