Inhomogeneous Defect Distribution in Mixed-Polytype Metal Halide Perovskites

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The competition between corner-, edge-, and face-sharing octahedral networks is a cause of phase inhomogeneity in metal halide perovskite thin-films. Here we probe the charged iodine vacancy distribution and transport at the junction between cubic and hexagonal polytypes of CsPbI3 from first-principles materials modeling. We predict a lower defect formation energy in the face-sharing regions, which correlates with a longer Pb–I bond length and causes a million-fold increase in local defect concentration. These defects are predicted to be more mobile in the face-sharing regions with a reduced activation energy for vacancy-mediated diffusion. We conclude that hexagonal phase inclusions or interfaces will act as defect sinks that could influence carrier dynamics in perovskite-based solar cells and electrical devices.

3403 Macromolecular and Materials Chemistry, 34 Chemical Sciences, 3406 Physical Chemistry
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Korea Health Industry Development Institute (HI19C1344)