Towards superior X-ray detection performance of two-dimensional halide perovskite crystals by adjusting the anisotropic transport behavior

Two-dimensional (2D) organic-inorganic hybrid halide perovskites have recently attracted extensive attention for electronic and optoelectronic applications due to their tunable properties and superior stability compared with their three-dimensional (3D) counterparts. Here, we report two kinds of organic cation (linear butylamine (BA) and branched isobutylamine (i-BA)) tailored CsPbBr₃crystals, namely (BA)₂CsPb₂Br₇and (i-BA)₂CsPb₂Br₇, grown by the temperature-cooling method. The organic cations' adjustable anisotropic structure, optoelectronic properties and X-ray detection performance have been systematically investigated. By shortening the spacer cation from BA to i-BA, the degree of anisotropy in 2D perovskite crystals is decreased, which may be ascribed to the reduced interlayer distance and barrier height resulting from the enhanced electronic coupling between neighboring organic cations. In particular, the device based on the (BA)₂CsPb₂Br₇crystal along theabplane exhibits superior X-ray sensitivity up to 13.26 mC Gy⁻¹cm⁻²at a relatively low electric field of 2.53 V mm⁻¹, owing to the multiple quantum well structure that restricts the charge carrier transport within theabplane resulting in efficient charge collection. Simultaneously, a superior long-term working stability is obtained under a high X-ray dose rate of 278.4 μGy s⁻¹. We anticipate that these findings will be helpful for the development of Ruddlesden-Popper perovskites for future research and applications.