Effects of Structural Phase Transitions on Hysteresis in Air‐Processed Organic–Inorganic Halide Perovskite Thin‐Film Transistors

Abstract

A comprehensive study on the effects of structural phase transitions (from −190 to 80 °C) on hysteresis in air‐processed methylammonium lead iodide (MAPbI3) thin‐film transistors (TFTs) is presented. The polarization effect of ordered MA+ ions and the migration of iodine ions are found to be the main causes of hysteresis in the orthorhombic (<−100 °C) and tetragonal (from −100 to 50 °C) phases, respectively. Large carrier concentration and lattice vibrations suppress the effects of ion migration in the cubic phase (>50 °C), resulting in negligible hysteresis. Hole current is found to vary marginally with temperature throughout the three phases. Electron current, however, is slightly smaller than hole current in the orthorhombic phase but rapidly increases with temperature until it exceeds hole current by three orders of magnitude in the tetragonal phase, and then decreases by an order of magnitude in the cubic phase due to scattering. Dedicating hole and electron transport, respectively to cold and hot conditions, may thus increase the operating temperature range for MAPbI3 devices. These findings provide fundamental insight into the origin of hysteresis in halide perovskite devices and guidelines for broadening their operating temperature window.