Alternating current bias capacitance imaging enables stable, high-performance perovskite X-ray detector

Metal halide perovskites are soft-lattice semiconductors with inherent high ionic concentrations. Their X-ray sensitivities are several orders of magnitude higher than semiconductors such as silicon, amorphous selenium, and cadmium telluride. However, due to the weak chemical bond and intrinsic ion migration of metal halide perovskites, nonlinear current responses can arise under both irradiation and direct current (DC) bias, leading to signal distortion and limiting device reliability.

In a study published in Science Advances, a team led by LI Yunlong from Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences, along with ZHU Ziyao and XU Xiumin from Anhui University, proposed an alternating current (AC) bias capacitance readout strategy for metal halide perovskite-based X-ray detectors, overcoming the challenge of intrinsic ion migration in current readout schemes.

By solving the Poisson's equation, the researchers revealed that high-ionic-density semiconductors undergo pronounced interfacial capacitance variations between dark and irradiated conditions. They then developed perovskite X-ray detectors that operate under low AC bias by using capacitance readout instead of current readout detection.

This capacitance readout scheme effectively mitigates the impact of ionic motion, preserving interfacial structure and ensuring long-term signal fidelity. Modulation transfer function measurements and imaging results demonstrated a spatial resolution of 167 μm with 150 μm pixels.

The developed perovskite X-ray detector achieved a theoretical maximum readout rate of up to 500 Hz per pixel under 1-kHz AC bias, matching the performance of conventional a-Se/TFT X-ray imaging systems. Besides, it achieved greater cost-effectiveness and scalability compared to high-frame-rate CMOS/CdTe-based detectors.

Furthermore, the researchers achieved high-resolution three-dimensional (3D) internal structure reconstruction with this detector based on polycrystalline MAPbI₃, which highlights its potential for applications in medical diagnostics, nondestructive evaluation, and security screening.

This study proposes a novel imaging modality for perovskite detectors, paving the way for the development of stable, low-cost, and scalable computed tomography systems.