Twin Distribution and Evolution in Large-Sized CsPbBr ₃ Single Crystals Engineered by Directional Annealing

Metal halide perovskite CsPbBr3 crystals have emerged as promising candidates for ionizing radiation detection. However, larger sized single crystals possessing greater commercial viability usually exhibit interwafer inhomogeneity and instability in both electrical and radiation detection properties, which is attributed to the material inhomogeneity in CsPbBr3 crystals, especially because of structural imperfections. This study reports the spatial distribution patterns of twin defects in a 60 mm diameter CsPbBr3 ingot grown by the vertical Bridgman method, where the twin-plane normals point toward the central axis of the ingot. Further, the twin evolution is evaluated through controlled movement under a gradient temperature field, with the rapid thermal treatment (10 mm/h) replicating the unidirectional twin characteristic of the as-grown state. Ultimately, directional annealing with a speed of 2 mm/h is adopted to eliminate the twins in CsPbBr3, in which the internal stress accumulated from octahedral twisting during the phase transition has sufficient time to relax and dissipate, thereby suppressing twin formation. The resulting mobility increased approximately 140% (from 10.25 to 24.89 cm2 V–1 s–1), and the resistivity is comparable to that of as-grown CsPbBr3 crystals free from twins. This research provides a novel approach to defect engineering in perovskite single crystals.