Methylamine-Dimer-Induced Phase Transition toward MAPbI₃ Films and High-Efficiency Perovskite Solar Modules

Perovskite films prepared with CH3NH2 molecules under ambient conditions have led to rapid fabrication of perovskite solar cells (PSCs), but there remains a lack of mechanistic studies and inconsistencies with operability in their production. Here the crystal structure of CH3NH2–CH3NH3PbI3 was analyzed to involve hydrogen bonds (CH3NH2···CH3NH3+) and has guided the facile, reproducible preparation of high-quality perovskite films under ambient conditions. Hydrogen bonds within CH3NH2···CH3NH3+ dimers were found in the CH3NH2–CH3NH3PbI3 intermediates, accompanied by 1D-PbI3– chains (δ-phase). The weakly hydrogen-bonded CH3NH2 molecules were easily released from the CH3NH2–CH3NH3PbI3 intermediates, contributing to rapid, spontaneous phase transition from 1D-PbI3– (δ-phase) to 3D-PbI3– (α-phase). Further introduction of CH3NH3Cl into the CH3NH2–CH3NH3PbI3 intermediates led to interruption of 1D-PbI3– transition into 0D-Pb2I9‑xClx5–(0 < x < 6), adjusting the phase transition route toward 3D-PbI3–. On the basis of the above understanding, CH3NH2 solution in ethanol and CH3NH3Cl were used for precursors and a best efficiency of 20.3% in PSCs was achieved. Large-scale modules (12 cm2 aperture area) fabricated by a dip-coating technology exhibited an efficiency up to 16.0% and outstanding stability over 10 000 s under continuous output. The developed preparation method of perovskite precursors and insightful research into the methylamine-dimer-induced phase transition mechanism have enabled the production of high-quality perovskite films with robust operability, showing great potential for large-scale commercialization.在环境条件下以甲胺（CH3NH2）分子制备的钙钛矿（Perovskite）薄膜实现了钙钛矿太阳能电池（Perovskite Solar Cells，PSCs）的快速制备，但目前仍缺乏相关机理研究，且其生产可操作性存在诸多不一致性。本文对CH3NH2–CH3NH3PbI3的晶体结构进行分析，发现其中存在氢键（CH3NH2···CH3NH3+），并以此为指导在环境条件下实现了高质量钙钛矿薄膜的简便、可重复制备。在CH3NH2–CH3NH3PbI3中间体中，CH3NH2···CH3NH3+二聚体内部存在氢键，同时伴随形成δ相一维碘化铅（1D-PbI3–）链。弱氢键结合的甲胺分子可轻易从该中间体中脱除，推动1D-PbI3–（δ相）快速自发相变至三维碘化铅（3D-PbI3–，α相）链。进一步向CH3NH2–CH3NH3PbI3中间体中引入甲胺氯（CH3NH3Cl），可阻断1D-PbI3–向0D-Pb2I9‑xClx5–（0 < x < 6）的相变路径，将相变路线调整为朝向3D-PbI3–的方向。基于上述研究认识，我们以乙醇中的甲胺溶液与甲胺氯作为前驱体，制备的钙钛矿太阳能电池最高效率达到20.3%。采用浸涂技术（dip-coating technology）制备的大面积模组（孔径面积12 cm²）效率可达16.0%，且在持续输出工况下具备超过10000秒的优异稳定性。本研究开发的钙钛矿前驱体制备方法，以及对甲胺二聚体诱导相变机理的深入解析，实现了可稳定量产的高质量钙钛矿薄膜制备，为其大规模商业化应用展现了巨大潜力。