Improving the crystallization quality of perovskite films is crucial for both the efficiency and stability of perovskite solar cells. However, the solid-state transition of formamidinium lead iodide perovskite thin films from the δ to α phase at high temperatures typically introduces a significant number of lattice defects, which in turn leads to increased carrier recombination rates and reduced humidity stability. Directly growing the α-phase perovskite phase from a precursor solution still remains a challenge. In this work, a low solubility, halogen-rich CsPb₂Br₅ crystal was introduced into the perovskite solution to regulate the crystallization behavior of the perovskite layer. It was demonstrated that the CsPb₂Br₅ nanocrystals pre-precipitated and induced the direct crystallization of the α-phase perovskite during the solution processing. The direct formation of the α-phase instead of the δ-phase effectively enhances the crystalline quality and reduces the defect density of the perovskite films. As a result, the corresponding device exhibits an enhanced power conversion efficiency of 25.55%, and the module efficiency with 14 cm² of active area reaches 22.35% (certified PCE is 21.7%). Thanks to the higher crystalline quality, these unencapsulated devices exhibit excellent operational stability at the maximum power point (∼92% efficiency retention after 1000 h).

中文翻译：

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CsPb2Br5 辅助直接结晶 3D 钙钛矿相，用于高效稳定的太阳能电池

提高钙钛矿薄膜的结晶质量对于钙钛矿太阳能电池的效率和稳定性至关重要。然而，甲脒碘化铅钙钛矿薄膜在高温下从δ相到α相的固态转变通常会引入大量的晶格缺陷，进而导致载流子复合率增加和湿度稳定性降低。从前驱体溶液中直接生长 α 相钙钛矿相仍然是一个挑战。在这项工作中，将低溶解度、富含卤素的CsPb ₂ Br ₅晶体引入钙钛矿溶液中以调节钙钛矿层的结晶行为。结果表明，CsPb ₂ Br ₅纳米晶体在溶液加工过程中预沉淀并诱导α相钙钛矿直接结晶。直接形成α相代替δ相有效地提高了钙钛矿薄膜的晶体质量并降低了缺陷密度。结果，相应器件的功率转换效率提高了25.55%，有效面积14 cm ²的模块效率达到22.35%（认证PCE为21.7%）。由于具有更高的晶体质量，这些未封装的器件在最大功率点表现出出色的运行稳定性（1000 小时后效率保持率为 92%）。