  Hybrid materials combining an organic matrix and high-Z nanomaterials show
potential for applications in radiation detection, allowing unprecedented
device architectures and functionality. Herein, novel hybrid organic-inorganic
systems were produced using a mixture of tungstate (CaWO$_4$ or ZnWO$_4$)
nanoparticles with a P3HT:PCBM blend. The nano-tungstates with a crystallite
size of 43 nm for CaWO$_4$ and 30 nm for ZnWO$_4$ were synthesized by the
hydrothermal method. Their structure and morphology were characterized by X-ray
diffraction and scanning electron microscopy. The hybrid systems were used to
fabricate direct conversion X-ray detectors able to operate with zero bias
voltage. The detector performance was tested in a wide energy range using
monochromatic synchrotron radiation. The addition of nanoparticles with high-Z
elements improved the detector response to X-ray radiation compared with that
of a pure organic P3HT:PCBM bulk heterojunction cell. The high dynamic range of
our detector allows for recording X-ray absorption spectra, including the fine
X-ray absorption structure located beyond the absorption edge. The obtained
results suggest that nanocrystalline tungstates are promising candidates for
application in direct organic-inorganic X-ray detectors.
