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

• DOI: 10.1038/srep35685
• Publication Date: 2016-10-21T10:06:23Z
• Authors: P. S. Whitfield; N. Herron; W. E. Guise; K. Page; Y. Q. Cheng; I. Milas; M. K. Crawford
• Keywords: Tetragonal crystal system; Orthorhombic crystal system; Ammonium iodide

Abstract We have examined the crystal structures and structural phase transitions of deuterated, partially deuterated hydrogenous organic-inorganic hybrid perovskite methyl ammonium lead iodide (MAPbI 3 ) using time-of-flight neutron synchrotron X-ray powder diffraction. Near 330 K high temperature cubic phases transformed to a body-centered tetragonal phase. The variation order parameter Q for this transition scaled with T as ∼ (T c −T) β , where is critical exponent was close ¼, predicted tricritical transition. However, we also observed coexistence over range in all cases, demonstrating that fact first-order, although still very tricritical. Upon cooling further, into low orthorhombic around 160 K, again via first-order Based upon these results, discuss impact photovoltaic performance MAPbI based solar cells.