Abstract In this paper, we synthesized lead-free cesium bismuth iodide (Cs3Bi2I9) perovskite films by solution process using one-step spin-coating technique. Formation of Cs3Bi2I9 perovskite was confirmed by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy analysis. The XRD analysis showed that all Cs3Bi2I9 perovskite films were polycrystalline in nature, with hexagonal crystal structure and preferred-orientation along (006) direction. The environmental stability of Cs3Bi2I9 perovskite was confirmed by XRD analysis and UV–visible spectroscopy. Multiple XRD and UV–Vis spectra taken after long time spans revealed the stable nature of Cs3Bi2I9 perovskite films. The UV–visible spectroscopy and photoluminescence analysis showed that the perovskite films absorbed strongly in the visible region and had an optical band gap of ~2.1 eV. Surface morphology of Cs3Bi2I9 perovskite over the entire substrate surface was investigated using scanning electron microscopy. Thermo-gravimetric analysis showed that Cs3Bi2I9 perovskite was thermally stable up to ∼ 420 °C. Finally, solar cells fabricated using Cs3Bi2I9 perovskite material showed maximum power conversion efficiency (PCE) of 0.17%, with short circuit current density of 1.43 mA/cm2, open circuit voltage of 0.37 V and fill factor of 32%. Applying compositional engineering and optimizing the device structure should further improve the PCE. These results are a significant step toward fabrication of Cs3Bi2I9 perovskite-based solar cells.

中文翻译：

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环境稳定的无铅碘化铯铋 (Cs3Bi2I9) 钙钛矿：合成到太阳能电池应用

摘要 在本文中，我们采用一步旋涂技术通过溶液法合成了无铅碘化铯铋（Cs3Bi2I9）钙钛矿薄膜。通过 X 射线衍射 (XRD)、拉曼光谱、X 射线光电子能谱和透射电子显微镜分析证实了 Cs3Bi2I9 钙钛矿的形成。XRD分析表明，所有Cs3Bi2I9钙钛矿薄膜本质上都是多晶的，具有六方晶体结构和沿（006）方向的择优取向。Cs3Bi2I9钙钛矿的环境稳定性通过XRD分析和紫外-可见光谱得到证实。长时间跨度后拍摄的多个 XRD 和 UV-Vis 光谱揭示了 Cs3Bi2I9 钙钛矿薄膜的稳定性。紫外-可见光谱和光致发光分析表明钙钛矿薄膜在可见光区有强烈吸收，光学带隙约为 2.1 eV。使用扫描电子显微镜研究了整个基板表面上 Cs3Bi2I9 钙钛矿的表面形态。热重分析表明，Cs3Bi2I9 钙钛矿在高达 420°C 的温度下是热稳定的。最后，使用 Cs3Bi2I9 钙钛矿材料制造的太阳能电池的最大功率转换效率 (PCE) 为 0.17%，短路电流密度为 1.43 mA/cm2，开路电压为 0.37 V，填充因子为 32%。应用成分工程和优化器件结构应进一步提高 PCE。这些结果是朝着制造 Cs3Bi2I9 钙钛矿基太阳能电池迈出的重要一步。