Appearance of efficient luminescence energy transfer in doped orthovanadate nanocrystals

This paper reports the detailed synthesis mechanism and the structural, morphological and optical characterization of ultraviolet (∼311 nm) excitable samarium doped gadolinium yttrium orthovanadate, (Gd,Y)VO₄:Sm³⁺, nanocrystals. X-ray diffraction and Rietveld refinement studies confirmed that the synthesized samples crystallize in a tetragonal structure with I41/amd space group. The enhanced photoluminescence intensity of (Gd,Y)VO₄:Sm³⁺ compared with the existing YVO₄:Sm³⁺ phosphor clearly indicates the significant role of Gd³⁺ ions. This has been attributed to the sensitization of the ⁶P_J energy level of Gd³⁺ ions by energy transfer from orthovanadate (VO₄³⁻) ions and subsequent energy trapping by Sm³⁺ ions. The energy transfer from VO₄³⁻ to Sm³⁺ via Gd³⁺ ions as intermediates and concentration quenching of Gd³⁺ luminescence are discussed in detail. The optical band gap of the as-prepared nanocrystals has been estimated using UV–vis–NIR absorption spectroscopy, which reveals a slightly higher band gap (3.75 eV) for YVO₄ as compared to GdYVO₄ (3.50 eV). Furthermore, confocal microcopy, decay parameters and Commission Internationale de l'Eclairage chromatic coordinates have supplemented these studies, which established the suitability of these nanophosphors for achieving spectral conversion in silicon solar cells.