Wide‐bandgap (WBG) formamidinium–cesium (FA‐Cs) lead iodide–bromide mixed perovskites are promising materials for front cells well‐matched with crystalline silicon to form tandem solar cells. They offer avenues to augment the performance of widely deployed commercial solar cells. However, phase instability, high open‐circuit voltage (V_oc) deficit, and large hysteresis limit this otherwise promising technology. Here, by controlling the crystallization of FA‐Cs WBG perovskite with the aid of a formamide cosolvent, light‐induced phase segregation and hysteresis in perovskite solar cells are suppressed. The highly polar solvent additive formamide induces direct formation of the black perovskite phase, bypassing the yellow phases, thereby reducing the density of defects in films. As a result, the optimized WBG perovskite solar cells (PSCs) (E_g ≈ 1.75 eV) exhibit a high V_oc of 1.23 V, reduced hysteresis, and a power conversion efficiency (PCE) of 17.8%. A PCE of 15.2% on 1.1 cm² solar cells, the highest among the reported efficiencies for large‐area PSCs having this bandgap is also demonstrated. These perovskites show excellent phase stability and thermal stability, as well as long‐term air stability. They maintain ≈95% of their initial PCE after 1300 h of storage in dry air without encapsulation.

中文翻译：

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酰胺催化的相选择结晶降低了宽带隙钙钛矿中的缺陷密度

宽带隙（WBG）甲ces铯（FA-Cs）碘化物-溴化铅混合钙钛矿是有前途的材料，可与晶体硅很好地匹配以形成串联太阳能电池。它们为增强广泛部署的商用太阳能电池的性能提供了途径。但是，相位不稳定，开路电压高（V _oc）缺陷，并且较大的磁滞现象限制了这种原本很有前途的技术。在这里，通过使用甲酰胺助溶剂控制FA-Cs WBG钙钛矿的结晶，可以抑制钙钛矿型太阳能电池中的光致相分离和滞后现象。高极性溶剂添加剂甲酰胺可诱导黑色钙钛矿相直接形成，绕过黄色相，从而降低薄膜缺陷的密度。其结果，最优化的钙钛矿WBG太阳能电池（的PSC）（Ë_克≈1.75电子伏特）表现出高的V _OC的1.23V的，降低的滞后，和17.8％的功率转换效率（PCE）。在1.1 cm ²上的PCE为15.2％太阳能电池，在具有此带隙的大面积PSC的报道效率中也最高。这些钙钛矿显示出极好的相稳定性和热稳定性，以及长期的空气稳定性。在干燥条件下（无封装）储存1300小时后，它们的初始PCE保持约95％。