Phase transformation during annealing in two-step sequential deposition has attracted widespread attention due to its importance in the preparation of superior perovskite films. However, previous studies have not adequately focused on the importance of purifying phase transition pathways during crystallization.
Different from the traditional mixed path, the team of professors Zhao Qing & Zhou Huanping of Peking University achieved a purification phase change path for α-FAPbI3 crystallization by introducing dimethylurea (DMU) into the lead iodide (PbI2 ) precursor solution. This multifunctional molecule was found to be able to engineer permeable porous PbI2 films and fundamentally regulate perovskite crystallization by forming a complete delta phase during the annealing process of the perovskite. The role of DMU in the purified phase transition pathway for α-FAPbI3 crystallization was revealed by in situ photoluminescence and all-tilt X-ray scattering (GIWAXS) studies.
The crystal quality of the final perovskite film was significantly improved, forming a single-crystal-like film. The best-performing perovskite solar cells (PSCs) achieved a conversion efficiency of 24.75%, with a higher fill factor of 83.25% and improved long-term stability of up to 3,600 hours. This work highlights the importance of purified phase change pathways to achieve superior crystal quality for high-performance perovskite photovoltaics.
X. Wang, G. Zheng, F. Gao, L. Li, C. Luo, C. Zhan, Y. Li, Y. Ma, X. Gao, H. Zhou, Q. Zhao, In Situ Study of Purified Phase Transition Path for α-FAPbI3 Crystallization. Adv. Energy Mater. 2024, 2303949.
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