Structures, Phase Transitions and Tricritical Behavior of the Hybrid Perovskite Methyl Ammonium Lead Iodide.

ABSTRACT: We have examined the crystal structures and structural phase transitions of the deuterated, partially deuterated and hydrogenous organic-inorganic hybrid perovskite methyl ammonium lead iodide (MAPbI₃) using time-of-flight neutron and synchrotron X-ray powder diffraction. Near 330?K the high temperature cubic phases transformed to a body-centered tetragonal phase. The variation of the order parameter Q for this transition scaled with temperature T as Q ? (T_c-T)^?, where T_c is the critical temperature and the exponent ? was close to ¼, as predicted for a tricritical phase transition. However, we also observed coexistence of the cubic and tetragonal phases over a range of temperature in all cases, demonstrating that the phase transition was in fact first-order, although still very close to tricritical. Upon cooling further, all the tetragonal phases transformed into a low temperature orthorhombic phase around 160?K, again via a first-order phase transition. Based upon these results, we discuss the impact of the structural phase transitions upon photovoltaic performance of MAPbI₃ based solar cells.

SUBMITTER: Whitfield PS 

PROVIDER: S-EPMC5073364 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature