Changes in near-bandgap photoluminescence in lead halide CsPbBr3 perovskite, subjected to extreme conditions

Abstract

Inorganic halide perovskites are promising materials for implementation in next-generation optoelectronics. Their mechanical sustainability is crucially important for successful industrial use. Herein, in the example of monoclinic perovskite CsPbBr3, we demonstrate that its photoluminescence (PL) characteristics are well preserved even after multiple phase transitions into disordered phases with much wider band gaps, under action of extreme conditions. We have subjected a single crystal of CsPbBr3 to multiple high-pressure treatments up to 12 GPa, across phase transitions into disordered phases, and measured temperature-dependent near-bandgap PL in both pristine and treated samples down to 7 K. While the PL characteristics of both samples were rather similar, the high-pressure-treated sample demonstrated a small band-gap increase, a more significant widening in the band gap with increasing temperature, a decrease in Rashba splitting and modifications in a broad defect PL band. We have shown that thermal expansion of the crystal lattice and exciton-phonon interactions cannot explain the above significant opening of the energy gap with temperature in the high-pressure treated sample. However, it can be explained by the appearance of an additional electron-phonon coupling mechanism, resulting from octahedral tilting and small structural distortions. Our findings suggest strong self-healing effects in CsPbBr3 perovskite, which allowed the restoration of its structural and optoelectronic properties after the intense disordering.