The attractive optoelectronic properties of MAPbI3 (MA = CH3NH3), one of the most common halide perovskites, can be complicated by its tetragonal → cubic structural phase transition just above room temperature. We show that decreasing the ambient pressure can move that phase transition by â 40 °C (at â 10-3 mbar). Our report also includes control experiments, which show that desorption of water or oxygen can be excluded as possible causes for the change in phase transition temperature. On the basis of diffraction data, we postulate that an optimum volume is required to initiate a T → C phase transition. The pressure-induced phase change in effect stabilizes the tetragonal phase for work around room temperature, even if some natural heating occurs.
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