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First-Principles Study of Ferroelastic Twins in Halide Perovskites
Andrew R Warwick1, Jorge Íñiguez2,3, Peter D Haynes1
1Department of Materials , Imperial College London , Exhibition Road , London SW7 2AZ , United Kingdom.
Abstract:
We present an ab initio simulation of 90° ferroelastic twins that were recently observed in methylammonium lead iodide. There are two inequivalent types of 90° walls that we calculate to act as either electron or hole sinks, which leads us to propose a mechanism for enhancing charge carrier separation in photovoltaic devices. Despite separating nonpolar domains, we show these walls to have a substantial in-plane polarization of ∼6 μC cm-2, due in part to flexoelectricity. We suggest this in turn could allow for the photoferroic effect and create efficient pathways for photocurrents within the wall.
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