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

Cs 3 Sb 2 Br 9, 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 Cs 3 Sb 2 Br 9 single crystals are not easily obtained. Herein, we apply the vertical Bridgman method to grow centimeter-sized Cs 3 Sb 2 Br 9 single crystal. The temperature-dependent crystal structure of Cs 3 Sb 2 Br 9 is in situ characterized in the temperature range of 100–400 K. A novel crystallographic and electronic structure anisotropy of the as-grown Cs 3 Sb 2 Br 9 single crystal along the transmission directions of [100] and [001] is experimentally and theoretically proved. Owing to the layered two-dimensional (2D) structure of Cs 3 Sb 2 Br 9, 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.