Polymer/ZnO hybrid materials for near-UV sensors with wavelength selective response

Solution-processed ZnO nanoparticles and wide-bandgap polymers were applied for hybrid UV sensors with bilayer heterojunction structure: indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/polymer/ZnO/Al. The photoresponse of the devices is mainly in the near-UV range (above 300 nm) under illumination through ITO side due to the filtering effect of the substrate, while the long-wavelength cutoff is decided by the bandgap of the polymers. With poly(9-vinylcarbazole) (PVK) employed as donor, the device exhibited a narrow-band response in the region of 300–360 nm. When PVK was replaced by a triarylamine-based polymer (TPD-BA) with lower bandgap, the response extended to 400 nm. However, if the backside of the ITO substrate was pre-coated with an organic filter layer, the response region narrowed down to 350(375)–400 nm. As a result, by using the hybrid devices reported here, wavelength selective response to near-UV becomes possible.