Structural Evolution in Methylammonium Lead Iodide
CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub>
- Publication date
- Publisher
Abstract
The
organic–inorganic hybrid perovskite, in particular,
methylammonium lead iodide (MAPbI<sub>3</sub>), is currently a subject
of intense study due to its desirability in making efficient photovoltaic
devices economically. It is known that MAPbI<sub>3</sub> undergoes
structural phase transitions from orthorhombic <i>Pnma</i> to tetragonal <i>I</i>4/<i>mcm</i> at ∼170
K and then to cubic <i>Pm</i>3̅<i>m</i> at
∼330 K. A tetragonal <i>P</i>4<i>mm</i> phase is also reported at 400 K considering total cation disorder
is not appealing due to its hydrogen-bonding capabilities. Resolving
this ambiguity of phase transition necessitates the study of the structural
evolution across these phases in our work using ab initio methods.
In this work, we show that the structural phase evolves from <i>Pnma</i> to <i>I</i>4/<i>mcm</i> to <i>P</i>4<i>mm</i> to <i>Pm</i>3̅<i>m</i> with increasing volume. The <i>P</i>4<i>mm</i> phase is a quasi-cubic one with slight distortion in
one direction from cubic <i>Pm</i>3̅<i>m</i> due to the rotation of MA cations. Biaxial strain on MAPbI<sub>3</sub> reveals that only the <i>Pnma</i> and <i>P</i>4<i>mm</i> phases are energetically stable at <i>a</i> < 9.14 Å and <i>a</i> > 9.14 Å, respectively.
The <i>Pnma</i>, <i>I</i>4/<i>mcm</i>, <i>P</i>4<i>mm</i>, and <i>Pm</i>3̅<i>m</i> phases can be stable under various uniaxial
strain conditions. Our study provides a clear understanding of the
structural phase transitions that occur in MAPbI<sub>3</sub> and provides
a guide for the epitaxial growth of specific phases under various
strain conditions