Isotropic-carrier-transport perovskite single crystal enables high-photoresponsivity solar-blind photodetectors for selective flame monitoring

Low-dimensional halide perovskites are promising candidates for solar-blind ultraviolet photodetectors. However, simultaneously achieving high photoresponsivity and low dark current remains challenging, due to the restricted transport and collection of photogenerated carriers caused by strong electronic localization. Here, guided by theoretical calculations of electronic structures, we report a solar-blind family of CsCdCl₃ perovskite single crystals, which features a 3D structural framework, delivering high carrier mobility of 7.54 cm²V⁻¹ s⁻¹ and a long carrier diffusion length of 6.96 μm. These achievements stem from the 3D electronic structure, enabling balanced carrier effective mass isosurfaces and enhanced band dispersion. CsCdCl₃-based solar-blind photodetectors yield a photoresponsivity of 35.4 A W⁻¹ and dark current of 1.0 × 10⁻¹² A. Moreover, the devices demonstrate a narrowband spectral response of only 20 nm with a spectral-rejection ratio of 1.96 × 10³, which enables spectral-selectivity flame detection, distinguishing various types of flames and showcasing potential in offshore oil flame monitoring.