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 their successful industrial use. Herein, using 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 the action of extreme conditions. We subjected a single crystal of CsPbBr₃ to multiple high-pressure treatments of up to 12 GPa, which underwent phase transitions into disordered phases, and measured the temperature-dependent near-bandgap PL of both the pristine and treated samples down to 7 K. While the PL characteristics of both the samples were rather similar, the high-pressure-treated sample demonstrated a small increase in its band-gap, a more significant widening of its band gap with increasing temperature, a decrease in Rashba splitting and modifications in its broad defect PL band. We showed that thermal expansion of the crystal lattice and exciton–phonon interactions cannot explain the above-mentioned significant widening of the energy gap with an increase in 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 intense disordering.