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Molecular Dynamics Simulations of Two-Step Process Enable Room-Temperature Synthesis of α-FAPbI3

preprint
submitted on 13.10.2020 and posted on 14.10.2020 by 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.

Funding

This research is funded by Swiss National Science Foundation through the NCCR MUST and individual grant 200020-185092.

History

Email Address of Submitting Author

paramvir.ahlawat@epfl.ch

Institution

École Polytechnique Fédérale de Lausanne

Country

Switzerland

ORCID For Submitting Author

0000-0003-2355-3663

Declaration of Conflict of Interest

The authors declare no conflict of interest.

Version Notes

This is original version

Exports