Organic chemistry

Crystallography

Metastability

Gene

Crystal structure

Genotype

Perovskite (structure)

Polymorphism (computer science)

Inorganic chemistry

Chemistry

Materials science

Iodide

Orthorhombic crystal system

Phase (matter)

Biochemistry

ACS Energy Letters

Room-temperature films of black-phase cesium lead iodide (CsPbI3) 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 CsPbI3 in an orthorhombic polymorph. We demonstrate that this polymorph is adopted by both powders and thin films of black-phase CsPbI3, 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 CsPbI3 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.

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

Cubic or Orthorhombic? Revealing the Crystal Structure of Metastable Black-Phase CsPbI3 by Theory and Experiment

Cubic or Orthorhombic? Revealing the Crystal Structure of Metastable Black-Phase CsPbI₃ by Theory and Experiment