Hydrogen-bond engineered supramolecular bismuth halides for flexible X-ray imaging without geometric distortion

Abstract

The development of flexible X-ray detectors is hindered by the fundamental challenge of fabricating semiconductor films that combine uniform morphology, high crystallinity, and mechanical robustness. Here, we report a hydrogen-bond engineered supramolecular (HBES) strategy that simultaneously overcomes these limitations in supramolecular bismuth halide cluster (PDBiI₅). By incorporating polyacrylic acid (PAA), we construct a dynamic supramolecular network that suppresses the coffee-ring effect during ultrasonic spray-coating by increasing solution viscosity and rationally modulating the kinetic balance between solvent evaporation and solute diffusion. Furthermore, the HBES approach modulates crystallization kinetics, prolonging the crystal growth time from 23 to 41 s and yielding densely packed films with enhanced crystallinity and significantly reduced defect states. These structural improvements endow the HBES-PDBiI₅ films with superior charge transport properties, including a high hole mobility of 2.16 cm² V⁻¹ s⁻¹ and an outstanding mobility-lifetime product of 9.1 × 10⁻⁴ cm² V⁻¹. Consequently, the resulting X-ray detectors achieve a record sensitivity of 19,009 µC Gy_air⁻¹ cm⁻² and an ultralow detection limit of 3.35 nGy_air s⁻¹, alongside excellent operational and environmental stability. Leveraging the mechanical robustness imparted by the dynamic supramolecular network, we demonstrate the first direct-type flexible X-ray imager, which retains 85% of its performance after 1000 bending cycles. This flexible imager effectively overcomes geometric distortion and vignetting effects, maintaining 85% edge photocurrent compared to 58% for rigid detectors, enabling clear imaging of curved objects. This work establishes a versatile supramolecular engineering paradigm for developing high-performance, flexible X-ray detection and imaging technologies.