Space‐Confined Growth for Thickness‐Controlled Cs 3 Bi 2 I 9 Perovskite Single Crystal Wafers for X‐Ray Detectors

The Cs₃Bi₂I₉ single crystal, as an all-inorganic non-lead perovskite, offers advantages such as stability and environmental friendliness. Its superior photoelectric properties, attributed to the absence of grain boundary influence, make it an outstanding X-ray detection material compared to polycrystals. In addition to material properties, X-ray detector performance is affected by the thickness of the absorption layer. Addressing this, a space-confined method is proposed. The temperature field is determined through finite element simulation, effectively guiding the design of the space-confined method. Through this innovative method, a series of thickness-controlled perovskite single crystal wafers (PSCWs) are successfully prepared. Corresponding X-ray detectors are then prepared, and the impact of single crystal thickness on device performance is investigated. With an increase in single crystal thickness, a rise followed by a decline in device sensitivity is observed, reaching an optimal value at 0.7 mm thickness at 40V mm^-1 with a device performance of 11313.6µC Gy^-1 cm^-2. This space-confined method enables the direct growth of high-quality perovskite single crystals with specified thickness, eliminating the need for slicing or etching.