Enhancement of X-ray detection efficiency by nanoparticles in organic semiconductor film

Organic semiconducting (OSC) X-ray detectors offer exciting opportunities for developing biocompatible, tissue-equivalent, flexible, and low-cost X-ray detection technologies. However, detection sensitivity is limited by the low X-ray attenuation efficiency of the organic active layer. Here, we present a novel strategy to enhance X-ray absorption by incorporating high atomic number ZnO nanoparticles (NPs) into 4-hydroxycyanobenzene (4HCB), an OSC material. A space-confined melt process was employed to fabricate well-oriented 4HCB/ZnO composite films. Strong π-π interactions between benzene rings in 4HCB promote layered growth, enabling uniform dispersion of ZnO NPs throughout the 4HCB film. Under 17.9 keV X-ray irradiation, the 4HCB/ZnO device exhibited a sensitivity of 477 μC Gy_air⁻¹ cm⁻², approximately 20 times higher than that of pure 4HCB film. This enhancement is primarily attributed to impact ionization induced by nanoparticles. Simulations confirmed that Mie scattering effect, resulting from the effective nanoparticle size, extends X-ray's radiation path length, leading to improved charge generation efficiency in the composite detectors. The composite film also exhibits high resistivity, fast mobility, a large on/off ratio, and a low detection limit, making the combination of inorganic NPs and OSC materials a promising strategy for achieving high-performance, low-cost X-ray detectors and imaging systems.