Structurally\nand Electronically Anisotropic Nature\nof Bridgman-Grown Cs<sub>3</sub>Sb<sub>2</sub>Br<sub>9</sub> Perovskite\nSingle Crystal toward Efficient Photodetector

Cs<sub>3</sub>Sb<sub>2</sub>Br<sub>9</sub>, as a sort\nof novel\nlead-free perovskite single crystal, has the merits of high carrier\nmobility and a long diffusion length. However, the large-sized and\nhigh-crystallized Cs<sub>3</sub>Sb<sub>2</sub>Br<sub>9</sub> single\ncrystals are not easily obtained. Herein, we apply the vertical Bridgman\nmethod to grow centimeter-sized Cs<sub>3</sub>Sb<sub>2</sub>Br<sub>9</sub> single crystal. The temperature-dependent crystal structure\nof Cs<sub>3</sub>Sb<sub>2</sub>Br<sub>9</sub> is <i>in situ</i> characterized in the temperature range of 100–400 K. A novel\ncrystallographic and electronic structure anisotropy of the as-grown\nCs<sub>3</sub>Sb<sub>2</sub>Br<sub>9</sub> single crystal along the\ntransmission directions of [100] and [001] is experimentally and theoretically\nproved. Owing to the layered two-dimensional (2D) structure of Cs<sub>3</sub>Sb<sub>2</sub>Br<sub>9</sub>, quantum confinement effects\nprolong the lifetime of hot carriers, leading to their accumulation\nwithin the Sb–Br plane along the [100] direction, thereby resulting\nin a higher density of electronic states. Accordingly, the [100] device\nexhibits a carrier mobility higher than that of the [001] device,\nwith the [100] device mobility being 4 orders of magnitude higher\nthan that of the [001] device at 423 K, showing a remarkable anisotropy.\nThe [100] device also shows responsivity ∼10 times higher than\nthat of the [001] device.