Ultraviolet photodetectors based on ZnO nanoparticles

Ultraviolet (UV) photodetectors based on ZnO nanoparticles (NPs) were fabricated and their optoelectronic properties were examined. The dominant photoluminescence (PL) peak of the ZnO NPs was located at a wavelength of 380 nm under the illumination of 325-nm wavelength light. The direct bandgap transition of the charge carriers at λ = 380 nm contributed to the photocurrent. The ratio of the photocurrent to the dark current (on/off ratio) was as high as 106, which is favorable for photodetectors. The decay time constant in the photoresponse was relatively small, while the rise time constant was relatively large. The reasons for the high on/off ratio and photoresponse characteristics are discussed in this paper.