The Relationships between UV Emission and Green Emission in ZnO Phosphor

ZnO phosphor was synthesized by annealing ZnO powder at low O2 partial pressure and in vacuum. ZnO has two emissions, which are located at about 380 nm (UV emission) and 510 nm (green emission). The UV emission can be attributed to the exciton emission, which is a single-center process, whereas the green emission is related to native defects, such as V
- O and V′Zn, which is a two-center (donor-acceptor) recombination process. The high-density excitation favors the UV emission, whereas the green emission likely appears in the samples annealed at low O2 partial pressure. It was shown that the energy transfer may occur from the UV emission center to the green emission center, and the exciton diffusion mechanism for the transfer was proposed.