Structurally and Electronically Anisotropic Nature of Bridgman-Grown Cs₃Sb₂Br₉ Perovskite Single Crystal toward Efficient Photodetector

Cs₃Sb₂Br₉, as a sort of novel lead-free perovskite single crystal, has the merits of high carrier mobility and a long diffusion length. However, the large-sized and high-crystallized Cs₃Sb₂Br₉ single crystals are not easily obtained. Herein, we apply the vertical Bridgman method to grow centimeter-sized Cs₃Sb₂Br₉ single crystal. The temperature-dependent crystal structure of Cs₃Sb₂Br₉ is <i>in situ</i> characterized in the temperature range of 100-400 K. A novel crystallographic and electronic structure anisotropy of the as-grown Cs₃Sb₂Br₉ single crystal along the transmission directions of [100] and [001] is experimentally and theoretically proved. Owing to the layered two-dimensional (2D) structure of Cs₃Sb₂Br₉, quantum confinement effects prolong the lifetime of hot carriers, leading to their accumulation within the Sb-Br plane along the [100] direction, thereby resulting in a higher density of electronic states. Accordingly, the [100] device exhibits a carrier mobility higher than that of the [001] device, with the [100] device mobility being 4 orders of magnitude higher than that of the [001] device at 423 K, showing a remarkable anisotropy. The [100] device also shows responsivity ∼10 times higher than that of the [001] device.