The current reported wide band gap perovskites based on iodide–bromine mixed halide composition would suffer from halide segregation. Here, we reported Cs-rich wide band gap pure-iodide Cs_xFA_1–x–yDMA_yPbI₃ (x > 0.5; y < 0.01) (denoted as CsFA) perovskites and successfully solved the problem of phase segregation in wide band gap perovskites. The comprehensive experimental and theoretical results indicated that, because of a mildly deformed octahedral framework, our fabricated CsFA pure-iodide wide band gap perovskites exhibit much higher stability than those mixed halide perovskites with similar band gaps under thermal or illumination stress. On the basis of a representative Cs_0.7FA_0.3–yDMA_yPbI₃ perovskite with a 1.65 eV band gap, the corresponding solar cells delivered a stable output of 19.40% with good photostability. Overall, our reported Cs-rich pure-iodide CsFA perovskites present promising candidates for wide band gap optoelectronic applications.

中文翻译：

---

用于高效光伏的稳定富铯甲脒/铯纯碘化物钙钛矿

目前报道的基于碘 - 溴混合卤化物成分的宽带隙钙钛矿会受到卤化物偏析的影响。在这里，我们报告了富含 Cs 的宽带隙纯碘化物 Cs _x FA _{1– x – y} DMA _y PbI ₃ ( x > 0.5; y< 0.01)（表示为 CsFA）钙钛矿并成功解决了宽带隙钙钛矿中的相分离问题。综合实验和理论结果表明，由于八面体骨架轻微变形，我们制造的 CsFA 纯碘化物宽带隙钙钛矿在热应力或光照应力下比具有相似带隙的混合卤化物钙钛矿表现出更高的稳定性。基于代表性的 Cs _0.7 FA _{0.3– y} DMA _y PbI ₃具有 1.65 eV 带隙的钙钛矿，相应的太阳能电池可提供 19.40% 的稳定输出和良好的光稳定性。总体而言，我们报道的富含 Cs 的纯碘化物 CsFA 钙钛矿为宽带隙光电应用提供了有希望的候选者。