Self-Powered Cs2AgBiBr6 Photon-Counting Detectors with Low Dark Count Rate at Room Temperature

Photon-counting detectors (PCDs) are highly anticipated for their exceptional ability to resolve weak optical signals that exist against a relatively low-background-noise environment, especially in medical computerized tomography. The performance of conventional silicon-based PCDs is often contingent upon cryogenic cooling, which restricts their practical applicability. Lead halide perovskites with wide bandgaps have garnered significant attention as a promising alternative, demonstrating remarkable performance in applications such as X-ray detection and photovoltaics. However, their potential for PCDs remains largely unexplored, and their commercial deployment is further hindered by inherent instability and lead toxicity. In this Letter, lead-free Cs2AgBiBr6 films were prepared by pulsed laser deposition (PLD) and their crystallinity and carrier transport properties were significantly enhanced through a postdeposition rapid thermal annealing process. The resulting photovoltaic device functioned as self-powered PCDs, achieving an ultralow dark count rate (DCR) of 56 cps·mm–2 at room temperature under zero bias, and maintaining a stable internal quantum efficiency (IQE) of approximately 70 ± 5% over a range of 103–108 incident photons. When coupled with a scintillator, the system achieved an energy resolution of 32.1% for 59.5 keV γ-rays. This work establishes lead-free double perovskite Cs2AgBiBr6 as a promising material paradigm for high-performance PCDs operating at room temperature.