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 (MAPbI3) 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(I1-xBrx)3 layer increases to 1.3 × 108 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 nGyair s-1 and a sensitivity to noise-current ratio of 7.27 × 1011 μC Gyair-1 A-1. By integrating the Br-doped MAPbI3 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.
Zhang et al. (Wed,) studied this question.