Suppression of ionic and electronic conductivity by multilayer heterojunctions passivation toward sensitive and stable perovskite X-ray detectors

Organic-inorganic hybrid perovskites are promising candidates for direct X-ray detection and imaging. The relatively high dark current in perovskite single crystals (SCs) is a major limiting factor hindering the pursuit of performance and stability enhancement. In this study, the contribution of dark current is disentangled from electronic (σ${}_e$) and ionic conductivity (σ${}_i$) and shows that the high σ${}_i$ dominates the dark current of MAPbBr${}_3$ SCs. A multilayer heterojunctions passivation strategy is developed that suppresses not only the σ${}_i$ by two orders of magnitude but also σ${}_e$ by a factor of 1.6. The multilayer heterojunctions passivate the halide vacancy defects and increase the electron and hole injection barrier by inducing surface p-type doping of MAPbBr${}_3$. This enables the MAPbBr${}_3$ SC X-ray detectors to obtain a high sensitivity of 19 370 µC Gy${}_{air}$${}^{-1}$ cm${}^{-2}$ under a high electric field of 100 V cm${}^{-1}$, a record high sensitivity for bromine self-powered devices, and a low detection limit of 42.3 nGy${}_{air}$ s${}^{-1}$. The unencapsulated detectors demonstrate a stable baseline after storage for 210 days and outstanding operational stability upon irradiation with an accumulated dose of up to 1944 m Gy${}_{air}$. (© 2023 Wiley‐VCH GmbH)