Crystallization Dynamics of Organolead Halide Perovskite by Real-Time X‑ray Diffraction

We analyzed the crystallization process of the CH₃NH₃PbI₃ perovskite by observing real-time X-ray diffraction immediately after combining a PbI₂ thin film with a CH₃NH₃I solution. A detailed analysis of the transformation kinetics demonstrated the fractal diffusion of the CH₃NH₃I solution into the PbI₂ film. Moreover, the perovskite crystal was found to be initially oriented based on the PbI₂ crystal orientation but to gradually transition to a random orientation. The fluctuating characteristics of the crystallization process of perovskites, such as fractal penetration and orientational transformation, should be controlled to allow the fabrication of high-quality perovskite crystals. The characteristic reaction dynamics observed in this study should assist in establishing reproducible fabrication processes for perovskite solar cells