Suppression of Ionic and Electronic Conductivity by Multilayer Heterojunctions Passivation Toward Sensitive and Stable Perovskite X‐Ray Detectors

Abstract

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 (σe) and ionic conductivity (σi) and shows that the high σi dominates the dark current of MAPbBr3 SCs. A multilayer heterojunctions passivation strategy is developed that suppresses not only the σi by two orders of magnitude but also σe 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 MAPbBr3. This enables the MAPbBr3 SC X‐ray detectors to obtain a high sensitivity of 19 370 µC Gyair−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 nGyair 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 mGyair.

High-Performance and Stable Perovskite X-ray Detection and Imaging Based on a Ti Cathode

“…Clearly, our device based on the Ti electrode can achieve the remarkably low detection limits under hard X-ray energy at both high and low electric fields. The sensitivity of the device with the Ti electrode has exceeded that of the MAPbBr 3 single-crystal X-ray detector based on other Schottky barrier contacts. ,− Compared to the methods of single-crystal component engineering, our approach is more feasible and scalable …”

Realizing low-ion-migration and highly sensitive X-ray detection by building g-C3N4 and CH3NH3PbI3 bulk heterojunction pellets

“…The resistivities of g-C 3 N 4 /MAPbI 3 pellets increased with an increase in g-C 3 N 4 content, from 3.03 × 10 6 Ω cm for the 1% 2D/3D sample to 3.38 × 10 7 Ω cm for 8% 2D/3D, which was almost 30-times higher than that of the pristine MAPbI 3 pellet. The increased resistivity may be attributed to two factors: first, for MAPbI 3 , its conductivity is contributed by electronic conductivity and ionic conductivity, 42 σ total = σ i + σ e where σ total is the total conductivity, σ i is the ionic conductivity, and σ e is the electronic conductivity. The higher resistivity of the 2D/3D sample may be due to the reduced σ i .…”

“…At high temperatures, σ i has a major role. E a can be determined by using the Nernst–Einstein equation to fit the temperature-dependent conductivity result: 42 where σ ( T ) is the temperature-dependent conductivity, σ 0 is a constant, T is the temperature, and k is the Boltzmann constant. As shown in Fig.…”

Insight into the Defect Chemistry and Ion Migration in Perovskite Fabricated by Hybrid Chemical Vapor Deposition

“…Galvanostatic electrical characterization which could separate ions and electrons conductivity in mixed conductor was conducted at 295 K at room temperature . The equivalent circuit is shown in Figure e.…”