Inhomogeneous defect distributions in mixed-polytype metal halide perovskites Young-Won Woo 1 , Zhenzhu Li 2 , Youngkwang Jung 1 , Ji-Sang Park 3 , Aron Walsh 1,2 1 Yonsei University, South Korea, 2 Imperial College London, UK, 3 Kyungpook National University, Korea The competition between corner-sharing and face-sharing networks is a cause of phase inhomogeneity in halide perovskite films. Here we probe the charged vacancy distribution and transport at the junction between cubic and hexagonal polytypes of CsPbI 3 from first principles materials modelling. We find a reduced defect formation energy in the face-sharing regions, which correlates with a longer Pb-I bond length and causes a 20 times increase in local defect concentration. Remarkably, defects are also more mobile at the polytype junction with a reduced activation energy for vacancy-mediated diffusion. We conclude that hexagonal phases inclusions or interfaces will act as defects sinks that could trap carriers and enhance current-voltage hysteresis in perovskite- based electrical devices. References 1. Sacha Fop et al. Nature Materials . 19 , 757 (2020)
2. Ilia M. Pavlovetc et al. ACS Energy Lett . 5 , 2802 (2020) 3. Tiarnan A. S. Doherty et al. Science . 374 , 6575, 1598 (2021)
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