Ultralow dark current soft X-ray detectors based on lead-free double perovskite Cs 2 AgBiBr 6

Abstract Soft X-ray detectors play a vital role in materials science, high-energy physics and medical imaging. Cs 2 AgBiBr 6 , a lead-free double perovskite, has gained attention for its excellent optoelectronic properties, stability, and nontoxicity. However, its fast crystallization and requirement for high-temperature annealing (>250 °C) often lead to inferior film quality, limiting its application in flexible devices. This study introduces an alloying strategy that significantly improves the quality of Cs 2 AgBiBr 6 thin films annealed at a reduced temperature of 150 °C. Devices based on the alloyed thin films exhibit an ultra-low dark current of 0.32 nA∙cm − 2 and a quantum efficiency of 725%. Furthermore, the first successful integration of Cs 2 AgBiBr 6 with a thin-film transistor backplane demonstrates its superior imaging performance, indicating that Cs 2 AgBiBr 6 is a promising material for next-generation soft X-ray sensors.