Effects of Ferroelastic Domain Walls on the Macroscopic Transport and Photoluminescent Properties of Bulk CsPbBr3 Single Crystals

The all-inorganic halide perovskite CsPbBr₃ has emerged as an excellent class of semiconductive and optoelectronic materials, in which its excellent properties are strongly related to the dynamics of its microstructures, i.e., ferroelastic domain walls. Here, the influence of ferroelastic domain walls on the macroscopic charge transport and photoluminescent properties in bulk single-crystal CsPbBr₃ is experimentally and intrinsically studied across wide temperature intervals. The larger area of the same domain orientation, along with denser and thinner domain walls in a bulk CsPbBr₃ single crystal, is formed through the Pnma↔P4/mbm↔Pm3̅m phase transitions. Remarkable motion of the domain walls near the P4/mbm↔Pm3̅m transition point is observed using in situ polarized optical microscopy. We initially observed a sharp decrease in resistivity after inducing larger areas with long-range order and denser, thinner domain walls in the temperature range from 273 to 343 K upon heating. In addition, the ferroelastic domain walls modulate exciton-phonon interactions and enhance radiative recombination in the CsPbBr₃ single crystal, which correlates with the decrease in resistivity. These results will motivate strategies to design high-performance semiconductive and optoelectronic materials or devices by inducing specific ferroelastic domain walls in metal halide perovskites.