Low noise ultraviolet photodetector with over 100% enhanced lifetime based on polyfluorene copolymer and ZnO nanoparticles

Stability and noise current of a hybrid UV photodetector with inverted planar heterojunction (PHJ) structure indium-tin-oxide/ZnO nanoparticles (NPs)/poly[9,9-dioctyl-fluorene-2,7-diyl]-copoly[diphenyl-p-tolyl-amine-4,4-diyl] (BFE)/Ag are investigated. ZnO NPs as the acceptor and BFE as the donor were deposited as the active layer. Under UV light illumination, light to dark current ratio of about 10(2) is observed at a very low bias voltage of -1.5 V. The spectral response of the device is located near UV region with a maximum responsivity of similar to 57 mA/W at wavelength of 350 nm. In particular, the prepared device exhibits remarkably higher photoresponse (similar to 350%) and stability (similar to 115%) enhancement under ambient condition compared to the reference device. In addition, the presented results show that the noise current of our device with PHJ structure is about an order of magnitude lower than that of commonly used bulk heterojunction system. (C) 2018 Wiley Periodicals, Inc