Sensitivity reduction mechanisms in organic perovskite X-ray detectors

The sensitivity reduction mechanisms in organic perovskite X-ray detectors are investigated in this paper by considering the dynamics of charge carrier transport across the perovskite photoconductor. A numerical model is proposed by considering bimolecular recombination, space charge effects, charge carrier trapping (monomolecular) and detrapping. The coupled continuity equations for both holes and electrons, trapping rate equations, and Poisson's equation across the photoconductor are simultaneously solved by a finite difference method. The numerical results are compared with COMSOL simulation. The change of sensitivity is not significant for a usual single exposure in diagnostic medical X-ray imaging applications. However, the sensitivity starts decreasing rapidly for an order of magnitude higher dose rate or accumulated dose under repeated exposures. The rapid change of electric field distribution (i.e., non-uniform electric field) is mainly responsible for the reduction of X-ray sensitivity in perovskite X-ray detectors.