Analytical modeling of photocurrent in double perovskite Cs[formula omitted]AgBiBr[formula omitted] X-ray detectors

Abstract

This work has developed a theoretical model to investigate the mechanisms of nonlinear steady-state photocurrent versus dose rate characteristics in Cs2AgBiBr6-based X-ray detectors. The photocurrent analysis on Cs2AgBiBr6-based X-ray detector shows that there is a photocurrent gain, primarily due to the presence of dark current. Charge injection from metal contacts is the primary source of dark current in Cs2AgBiBr6. The accumulation of X-ray induced ions near the electrodes elevates the metal/perovskite interface electric field, and hence increases the charge injection with the X-ray dose. The Schottky barrier height for charge injection is found to be dependent on the X-ray dose as well. Therefore, the variation of dark current under X-ray exposures are mainly responsible for the non-linear steady-state photocurrent. The comparison of the model with the experimental results reveals the accumulated ion concentrations and effective barrier heights.