A Review on Strategies to Fabricate and Stabilize Phase‐Pure α‐FAPbI3 Perovskite Solar Cells

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Formamidinium lead triiodide (FAPbI3) with an optimal bandgap of 1.48 eV and superior thermal stability is regarded as one of the most promising perovskite‐based materials for the application in efficient single‐junction solar cells. However, the metastable properties of FAPbI3 due to phase transition from photoactive α phase into an undesired nonperovskite δ phase in ambient conditions become the major factors limiting its further development. Challenges remain in stabilizing α phase structure and preparing phase‐pure α‐FAPbI3 films for high‐efficiency and stable perovskite solar cells (PSCs) devices. Herein, the recent research progress on the strategies is reviewed to fabricate phase‐pure α‐FAPbI3 perovskite and the advances in their photovoltaic application. The physical parameters affecting the phase instability of intrinsic FAPbI3 are first discussed, followed by various methodologies for regulating phase transition behavior, such as additive engineering, solvent optimization, dimensionality engineering, and fabrication techniques. Finally, the fundamental challenges of preparing efficient α‐FAPbI3 PSCs are discussed, and the perspectives on the further development of high‐quality phase‐pure α‐FAPbI3 for reliable PSCs are proposed.