First-principles Study of Water Insertion Process on MAPbI₃Surface

We computationally investigate an insertion process of water into the methylammonium lead halide perovskite (MAPbI₃), which has been attracting considerable interest during recent years due to its high performance in solar-cell application [1]. The rapid decomposition of MAPbI₃ reaction with water has been recognized to be a major obstacle to outdoor applications [2]. To overcome this drawback process, it is important to identify the initial stage of water insertion into the MAPbI₃. The first-principles calculation based on the density-functional theory is performed to investigate the water insertion process on outer surface layer of MAPbI₃ slab model. Using the Nudged Elastic Band method, we find that the initial insertion process follows the three steps; approaching, re-orienting and finally sinking into the perovskite layer. This process requires approximately 0.60 eV to overcome an energy barrier, which agrees with an in situ X-ray diffraction (XRD) measurement of the reaction threshold of water molecules with the MAPbI₃ crystal at room temperature [3].
References:
[1] W. E. Sha et al., Appl. Phys. Lett. 106, 221104 (2015).
[2] U.G. Jong et al., J. Mater. Chem. A 6, 1067 (2018).
[3] M. Hada, M.A.A. Asad et al., submitted.