Atomistic Insights Into the Degradation of Inorganic Halide Perovskite CsPbI3: A Reactive Force Field Molecular Dynamics Study

Mike Pols; José Manuel Vicent-Luna; Ivo Filot; Adri C T van Duin; Shuxia Tao

doi:10.1021/acs.jpclett.1c01192

Atomistic Insights Into the Degradation of Inorganic Halide Perovskite CsPbI₃: A Reactive Force Field Molecular Dynamics Study

J Phys Chem Lett. 2021 Jun 17;12(23):5519-5525. doi: 10.1021/acs.jpclett.1c01192. Epub 2021 Jun 7.

Authors

Mike Pols^{1

2

3}, José Manuel Vicent-Luna^{1

3}, Ivo Filot^{2

3}, Adri C T van Duin⁴, Shuxia Tao^{1

3}

Affiliations

¹ Materials Simulation & Modelling, Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.
² Laboratory of Inorganic Materials Chemistry, Schuit Institute of Catalysis, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
³ Center for Computational Energy Research, Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.
⁴ Department of Mechanical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, United States.

Abstract

Halide perovskites make efficient solar cells but suffer from several stability issues. The characterization of these degradation processes is challenging because of the limited spatiotemporal resolution in experiments and the absence of efficient computational methods to study these reactive processes. Here, we present the first reactive force field for molecular dynamics simulations of the phase instability and the defect-induced degradation in CsPbI₃. We find that the phase transitions are driven by the anharmonic fluctuations of the atoms in the perovskite lattice. At low temperatures, the Cs cations tend to move away from their preferential positions, resulting in worse contacts with the surrounding metal halide framework which initiates the conversion to a nonperovskite phase. Moreover, our simulations of defective structures reveal that, although both iodine vacancies and interstitials are mobile in the perovskite lattice, the vacancies have a detrimental effect on the stability, leading to the decomposition of perovskites to PbI₂.