Efficient ultraviolet emission of ZnS nanospheres: Co doping enhancement

High-quality ultraviolet (UV) emission materials are essential for making short-wavelength light-emitting diodes and diode lasers. We report here that efficient ultraviolet luminescence at room-temperature can be obtained in ZnS nanospheres synthesized with an economical and simple chemical bath deposition method. The homogeneity, crystallinity and size of cubic ZnS nanospheres lead to a narrow and strong UV emission centered at 345 nm. Interestingly, Co doping dramatically enhances the near band edge UV emission and suppress the deep-level (DL) emission due to the improvement of crystallinity and the decrease of the DL defects. This work suggests that Co-doped ZnS is a promising candidate for ultraviolet functional material.