Evaluation of organic perovskite photoconductors for direct conversion X-ray imaging detectors

Abstract

Enhancing the sensitivity of a direct conversion flat panel X-ray imaging detector with minimum manufacturing cost has been a major dream for long decades. This criterion has been recently addressed by the usage of MAPbX3 (MA is CH3NH3 and X is a halogen atom such as Cl, I, or Br) perovskite in X-ray imaging detectors. Though MAPbI3 has shown large area deposition capability and good X-ray sensitivity, it has to fulfil other criteria such as low dark current, high spatial resolution and high signal to noise transfer capabilities. This paper evaluates the imaging performances such as X-ray sensitivity, detective quantum efficiency (DQE) and modulation transfer function (MTF) of organic perovskites (e.g., MAPbI3 and MAPbBr3) with comparison to amorphous selenium (a-Se). These perovskite materials have slightly higher linear attenuation coefficients than a-Se and the expected X-ray sensitivity of these two perovskite photoconductors are higher than a-Se. The mechanisms of the dark current and photocurrent gain in MAPbI3 detector are also investigated. The MAPbI3 detector shows some photocurrent gain, which is due to the enhanced electron injection under X-ray illumination. The expected theoretical zero spatial frequency DQE of the MAPbI3 detectors is similar to that of a-Se while the MAPbBr3 detector establishes a better DQE than a-Se. The expected MTF of the MAPbBr3 detectors is similar to that of a-Se while the MAPbI3 shows worse resolution than a-Se. Based upon our theoretical investigation, we believe that the organic perovskite can find its state of the art in near future if rigorous research for improving the charge carrier transport properties and optimizing its detector structure for low dark current were to be made.