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Manuscript+SI.pdf (14.52 MB)
Molecular Dynamics Simulations of Two-Step Process Enable Room-Temperature Synthesis of α-FAPbI3
Preprints are manuscripts made publicly available before they have been submitted for formal peer review and publication. They might contain new research findings or data. Preprints can be a draft or final version of an author's research but must not have been accepted for publication at the time of submission.
submitted on 13.10.2020 and posted on 14.10.2020by Paramvir Ahlawat, Haizhou Lu, Amita Ummadisingu, Haiyang Niu, Michele Invernizzi, Shaik M. Zakeeruddin, Anders Hagfeldt, Michael Grätzel, Ursula Rothlisberger, Michele Parrinello
It is well established that the lack of understanding the crystallization process in two-step sequential deposition has a direct impact on efficiency, stability and reproducibility of perovskite solar cells. Here, we try to understand the solid-solid phase transition occuring during two-step sequential deposition of methylammonium lead iodide and formamidinium lead iodide. Using metadynamics, X-ray diffraction and Raman spectroscopy, we reveal the microscopic details of this process. We find that the formation of perovskite proceeds through intermediate structures and report polymorphs found for methylammonium lead iodide and formamidinium lead iodide. From simulations, we discover a possible crystallization pathway for the highly efficient metastable α-phase of formamidinium lead iodide. Guided by these simulations, we perform experiments that results in the room temperature crystallization of α-formamidinium lead iodide.