Iodide-free tribromide-based perovskites, with their wide bandgap of over 2.0 eV, are highly regarded as potential candidates for a photoelectrochemical water splitting system and the topmost cell in tandem solar cell. Herein, we report on the importance of microtuning of the crystal lattice by cesium incorporation into the A-site on low temperature processed formamidinium lead tribromide (CH(NH₂)₂PbBr₃ = FAPbBr₃) perovskite films. The partial incorporation of cesium bromide (CsBr) into the FAPbBr₃ film tunes crystal-lattice interactions, resulting in a high-purity cubic crystal system with preferred orientation. An entirely low temperature processed planar photovoltaic device assembled with FAPbBr₃ containing 8% Cs (Cs_0.08FA_0.92PbBr₃) exhibited an optimum PCE (power conversion efficiency) of 8.56% with a V_oc (open-circuit voltage) of 1.516 V, which is higher than the PCE of 7.07% and V_oc of 1.428 V of the FAPbBr₃ device. Photoluminescence-intensity and temporal-imaging measurements were conducted by laser scanning confocal time-resolved microscopy (LCTM), which revealed that CsBr incorporation into a FAPbBr₃ film significantly suppresses the nonradiative recombination pathways and homogenizes the spatial distribution of photoluminescence. It was visualized that the incorporation of CsBr in FAPbBr₃ directly affects the bulk defect and photoluminescence properties, which provides evidence that Cs ions surely alleviate the segregation and aggregation of ions in the perovskite film. Notably, the Cs_0.08FA_0.92PbBr₃ film, with a carrier lifetime of about 270 ns, exhibited a 1.37-fold longer radiative recombination time than that (210 ns) observed for the FAPbBr₃ film. Furthermore, aging experiments without encapsulation under ambient (in air for 2000 h) and severe (65 °C and 65% RH for 500 h) conditions revealed that the Cs_0.08FA_0.92PbBr₃ devices were more robust than the FAPbBr₃ devices.

中文翻译：

---

宽带隙钙钛矿晶格平面的微调谐，可用于超过1.5 V的高效且坚固的高压平面太阳能电池

不含碘化物的三溴化物基钙钛矿，其带隙超过2.0 eV，被广泛认为是光电化学水分解系统和串联太阳能电池中最高电池的潜在候选者。在这里，我们报告了通过在低温处理的甲ami三溴化铅（CH（NH ₂）₂ PbBr ₃ = FAPbBr ₃）钙钛矿薄膜上的A位掺入铯来微调晶格的重要性。将溴化铯（CsBr）部分掺入FAPbBr ₃膜可调节晶格相互作用，从而产生具有优选取向的高纯度立方晶系。与FAPbBr组装在一起的完全低温处理的平面光伏器件₃含8％CS（CS _0.08 FA _0.92 PbBr ₃）表现出8.56％的最佳PCE（功率转换效率）与V _OC 1.516 V，这比的7.07％和PCE更高的（开路电压）V FAPbBr ₃器件的1.428 V的_oc。通过激光扫描共聚焦时间分辨显微镜（LCTM）进行光致发光强度和时间成像测量，结果表明将CsBr掺入FAPbBr ₃膜中可显着抑制非辐射重组途径并使光致发光的空间分布均匀。可以看出，CsBr在FAPbBr ₃中的掺入直接影响体缺陷和光致发光性能，这提供了Cs离子确实减轻钙钛矿薄膜中离子的偏析和聚集的证据。值得注意的是，具有约270 ns载流子寿命的Cs _0.08 FA _0.92 PbBr ₃薄膜，其辐射复合时间比FAPbBr ₃薄膜（210 ns）长1.37倍。此外，在环境（在空气中持续2000小时）和严酷（65°C和65％RH持续500 h）条件下未进行封装的老化实验表明，Cs _0.08 FA _0.92 PbBr ₃器件比FAPbBr ₃器件更坚固。