Effects of Electrode Size Mismatch on the Apparent Sensitivity of Perovskite X-Ray Detectors

Metal halide perovskite X-ray detectors have demonstrated sensitivities over one thousand times higher than those of commercial X-ray detectors. However, there is currently no standardized sensitivity testing protocol. In this study, we found that the electrode configuration significantly influences sensitivity values. The measured apparent sensitivity could be extremely high, when electrode is small and mismatched with X-ray active layer. This phenomenon arises from collection of charge carriers in the range of approximately 1 mm around the electrode and is intensified with higher carrier mobility and lifetime product, as well as applied bias. The phenomenon can be mitigated by incorporating guard rings. This work highlights a significant testing challenge often overlooked in X-ray detector sensitivity characterization, which could lead to serious overestimation of sensitivity, especially for materials with high mobility-lifetime product such as perovskite.