1Department of Physics, University of the Free State (Qwa-Qwa Campus), Private Bag X 13, Phuthaditjhaba, 9866, South Africa
2School of Physics, University of the Witwatersrand, Private Bag 3, Wits, 2050, South Africa
Adv. Mater. Lett., 2017, 8 (6), pp 735-740
Publication Date (Web): Apr 30, 2017
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Samarium (Sm3+) and thulium (Tm3+) co-activated yttrium orthovanadatephosphate YV0.5P0.5O4: Sm3+, Tm3+ powder phosphors were synthesized by solution combustion method and were annealed at 900oC for 2 hours. The x-ray diffraction patterns confirmed that the tetragonal structure of YV0.5P0.5O4 was crystallized. The patterns consisted of peaks from YVO4 and YPO4 suggesting that our product was an admixture of both compounds. The scanning and transmission electron microscopy image showed an agglomeration of particles with different sizes and shapes. The UV-vis reflectance spectra showed a broad absorption band extending from 200 — 550 nm associated with the O→V charge transfer transitions of [VO4]3−. The photoluminescence (PL) data of singly doped phosphors showed one blue emission peak at 477 nm (1G4— 3H6) and three emission peaks at 567 nm (6G5/2 — 6H5/2), 603 nm (6G5/2 — 6H7/2) and 650 nm (6G5/2 — 6H9/2) corresponding to transitions of Tm3+ and Sm3+ ions respectively. The PL data from the Sm3+- Tm3+ co-doped systems demonstrated an enhancement of visible emission of Tm3+ by down-conversion process that involves energy capture by the host last and Sm3+ that was subsequently transferred to Tm3+. These materials are evaluated as possible candidates to improve the power conversion efficiency of dye-sensitized solar cells.
Orthovanadatephosphate, phosphors, photoluminescence, down-conversion, energy transfer.