Journal
CHEMISTRY OF MATERIALS
Volume 29, Issue 14, Pages 6003-6011Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.chemmater.7b01781
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Funding
- Washington University
- Ralph E. Powe Junior Faculty Enhancement Award from Oak Ridge Associated Universities
- National Science Foundation [ACI-1053575]
- NIH grants [1S10RR022984-01A1, 1S10OD018091-01]
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Methylammonium lead iodide (CH3NH3PbI3 or MAPbI(3)) perovskite is a promising new photovoltaic material with high power conversion efficiency. However, its perovskite phase with corner-connected PbI6 octahedra shows poor environmental stability. More recently, MAPbI(3) has been shown to be thermodynamically unstable with a positive formation enthalpy. Here, using first-principles density functional theory calculations, we predict a layered hexagonal phase of MAPbI(3) consisting of infinite chains of face-shared PbI6 octahedra with P6(3)mc space-group symmetry to be thermodynamically the most stable phase for a wide range of volume and temperature compared to any of the experimentally observed perovskite phases with a different tilt pattern of the corner-connected octahedra. The predicted hexagonal phase is also dynamically stable without any soft phonon modes. The change from corner to face-shared connectivity in the hexagonal phase leads to a predicted band gap of 2.6 eV and a band structure that favors highly anisotropic charge transport.
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