The methylammonium lead triiodide perovskite is normally described as having three phases: a cubic lattice at high temperature, a tetragonal lattice at room temperature, and an orthorhombic lattice at low temperature. We present an alternative description of the room temperature structure in an anisotropic, lower-symmetry orthorhombic spacegroup. Treatment of the perovskite in the alternative lower spacegroup results in a structural model that features ordering of the methylammonium cations, as opposed to the usual description of these cations as randomly disordered in the room temperature phase. Thus, while the heavy lead and iodine atoms closely approximate a tetragonal lattice, the evidence indicates that the ordering of the light methylammonium cations breaks the symmetry, giving an orthorhombic description. The required anisotropy is consistent with macroscopic crystal morphology and anisotropic photoluminescence lifetime measurements, which differ at the various crystal faces. Implications on the operation of methylammonium lead triiodide perovskite photovoltaic devices will be discussed.

Inherent directional order of methylammonium cations in lead-iodide perovskite.

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.