Journal
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY
Volume 16, Issue 1, Pages 619-625Publisher
AMER SCIENTIFIC PUBLISHERS
DOI: 10.1166/jnn.2016.10812
Keywords
Rare Earth; ZnO; White Light; Luminescence Dynamics; Energy Transfer
Categories
Funding
- National Natural Science Foundation of China [10774031, 21271048]
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In order to expand the use of ZnO in advanced display and lighting device applications, such as distinguishable emissive flat panel displays and liquid crystal display backlights, Eu3+/Dy3+-codoped ZnO nanocrystals were synthesized using a low temperature wet chemical doping technique and chemical surface modification. X-ray diffraction patterns revealed that co-doping Eu3+ and Dy3+ does not change the wurtzite structure of ZnO. A high-resolution TEM image showing obvious lattice fringes confirmed the high crystallinity of the nanosized sample. The luminescence and dynamics of Eu3+/Dy3+-codoped ZnO nanocrystals of various doping concentrations were studied under ultraviolet excitation. Excitation into the ZnO conduction band was also studied. ZnO doped with Eu3+ and Dy3+ ions exhibited a strong blue (483 nm) emission from the F-4(9/2) -> H-6(15/2) transition of Dy3+ ions, a yellowish-green (575 nm) emission from the F-4(9/2) -> H-6(13/2) transition of Dy3+ ions and a red (612 nm) emission from the D-5(0) -> F-7(2) transition of Eu3+ ions, without a defect background. Undoped ZnO emitted a broadband green light, demonstrating an efficient energy transfer from the ZnO host to the Eu3+ and Dy3+ ions. Moreover, energy transfer from the Eu3+ ions to the Dy3+ ions in the ZnO host was also observed by analyzing luminescence decay curves. The luminescence dynamics of the Eu3+/Dy3+-codped ZnO sample indicate that as the Eu3+ concentration increased, both the rise and the decay time constants of the H-4(9/2) level of the Dy3+ ions became longer, while the decay time constants of the 5D0 level of the Eu3+ ions became shorter, suggesting an energy transfer from the Eu3+ ions to the Dy3+ ions in the ZnO host. Furthermore, by adjusting the doping concentration ratio of Eu3+ and Dy3+ ions, the Eu3+/Dy3+-codoped ZnO phosphors emitted strong white luminescence with a high color purity and high color rendering index. The results indicate that the Eu3+/Dy3+-codoped ZnO phosphors are promising light-conversion materials, and have the potential to be used in field emission display devices and LCD backlights.
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