Ferroelastic Domains Enhanced the Photoelectric Response in a CsPbBr₃ Single-Crystal Film Detector

The ferroic domain, in metal halide perovskites (MHPs) at a low symmetry phase, was reported to affect optoelectronic properties. Building the relationship between ferroic domains and optoelectronic properties of MHPs will be a non-trivial task for understanding the charge transport mechanism. Here, high-quality CsPbBr₃ single-crystal films (SCFs) were successfully grown by a cast-capping method. Through the phase transition process by heating and cooling the sample, dense domains in CsPbBr₃ SCFs were formed and observed by an in situ polarized optical microscope. These domains were identified as 90° rotation twins by electron backscattered diffraction and transmission electron microscopy. Interestingly, the photocurrent response was dramatically enhanced after introducing ferroelastic domains. The highest responsivity, external quantum efficiency, and detectivity are 380 mA/W, 130%, and 12.9 × 10¹⁰ Jones, respectively, which are surprisingly 25.03, 25, and 7.8 times higher than those of the as-grown CsPbBr₃ SCF, respectively, which may be attributed to the function of the domain wall of separating electrons and holes.