Cubic or Orthorhombic? Revealing the Crystal Structure of Metastable Black-Phase CsPbI 3 by Theory and Experiment

作者：Rebecca J. Sutton, Marina R. Filip, Amir A. Haghighirad, Nobuya Sakai, Bernard Wenger, Feliciano Giustino, Henry J. Snaith · 发表于：ACS Energy Letters · 年份：2018 · DOI：10.1021/acsenergylett.8b00672 · 被引用次数：604 · 研究领域：Perovskite Materials and Applications、Solid-state spectroscopy and crystallography、Thermal Expansion and Ionic Conductivity

Room-temperature films of black-phase cesium lead iodide (CsPbI 3 ) are widely thought to be trapped in a cubic perovskite polymorph. Here, we challenge this assumption. We present structural refinement of room-temperature black-phase CsPbI 3 in an orthorhombic polymorph. We demonstrate that this polymorph is adopted by both powders and thin films of black-phase CsPbI 3, fabricated either by high- or low-temperature processes. We perform electronic band structure calculations for the orthorhombic polymorph and find agreement with experimental data and close similarities with orthorhombic methylammonium lead iodide. We investigate the structural transitions and thermodynamic stability of the various polymorphs of CsPbI 3 and show that the orthorhombic polymorph is the most stable among its other perovskite polymorphs, but it remains less stable than the yellow nonperovskite polymorph.