Compositional Engineering for Low-Dark-Current Perovskite X-ray Detectors

Polycrystalline perovskites have attracted extensive interest in the field of X-ray detection/imaging due to their excellent compatibility with scalable processing. However, despite recent advances, polycrystalline perovskite X-ray direct detectors are plagued by the relatively high dark currents in imaging applications. Herein, we experimentally demonstrate that the dark current of polycrystalline perovskite X-ray detectors can be controlled by tuning the composition of perovskites. In particular, the incorporation of bromine (Br) into methylammonium lead iodide (MAPbI 3 ) modifies the bandgap, increases electrical resistance, reduces the defects, improves the crystallinity, and suppresses the nonradiative recombination, thereby comprehensively causing the reduction of dark currents. At a doping concentration of 15%, the bulk resistivity of MAPb(I 1– x Br x ) 3 layer increases to 1.3 × 10 8 Ω·cm, leading to a low dark current density down to 0.801 nA·cm –2 . Consequently, the X-ray detector shows a low detection limit of 118.4 nGy air s –1 and a sensitivity to noise-current ratio of 7.27 × 10 11 μC Gy air –1 A –1 . By integrating the Br-doped MAPbI 3 X-ray detector into a readout integrated circuit, the X-ray imager exhibits high-quality imaging capability. The results reveal a simple and effective strategy to minimize dark currents in perovskite X-ray detectors, and the detector has high potential in high-performance X-ray flat-panel imagers for industrial and medical applications.