Hybrid Perovskite Phase Transition and Its Ionic, Electrical and Optical Properties

Hybrid perovskite solar cells (PSCs) under normal operation will reach a temperature above similar to 60 degrees C, across the tetragonal-cubic structural phase transition of methylammonium lead iodide (MAPbI(3)). Whether the structural phase transition could result in dramatic changes of ionic, electrical and optical properties that may further impact the PSC performances should be studied. Herein, we report a structural phase transition temperature of MAPbI(3) thin film at similar to 55 degrees C, but a striking contrast occurred at similar to 45 degrees C in the ionic and electrical properties of MAPbI(3) due to a change of the ion activation energy from 0.7 eV to 0.5 eV. The optical properties exhibited no sharp transition except for the steady increase of the bandgap with temperature. It was also observed that the activation energy for ionic migration steadily increased with increased grain sizes, and reduction of the grain boundary density reduced the ionic migration.