Oriented Heterodimensional Perovskite Crystals for Self‐Powered X‐Ray Detection with Reduced Dark Current and Anisotropic Response

Abstract X‐ray detectors utilizing 2D/3D heterodimensional perovskites have achieved great success. However, the labile nature of halide perovskites generally results in structures with random orientations and interfaces, which in turn increases the dark noise of X‐ray detectors, hindering their use in low‐dose X‐ray detection. Here, it is shown that both anisotropy and ultralow dark current can be achieved in self‐powered X‐ray detectors using well‐oriented 2D/3D heterodimensional perovskite crystals (HPCs). A halide diffusion‐promoted welding approach is devised to create the oriented HPCs, enabling two distinct configurations: A lateral orientation where the inorganic frameworks of the two phases are perpendicular, and a vertical orientation with parallel inorganic slabs. The different crystalline orientations produce unique anisotropic X‐ray detecting performance of 2D/3D HPCs, with a large anisotropic ratio of 4. Moreover, a self‐powered X‐ray detector using vertical HPC exhibits a greatly suppressed dark current density of 0.17 nA cm −2 and a low detection limit of 77 nGy air s −1 , enabling high‐resolution X‐ray imaging. In contrast, the lateral devices show higher X‐ray sensitivity (1850 µC Gy air −1 cm −2 ) at zero bias. This work reveals the interplay between crystalline orientation and X‐ray detection performance, opening new possibilities for developing low‐cost, low‐noise X‐ray detectors.