Enhanced photoluminescence and energy transfer of Li+ co-doped GdPO4·H2O:Tb3+,Ce3+ green phosphors

A series of luminescent emission-tunable Gd_0.85-xTb_0.15PO₄·H₂O:xCe³⁺ (x = 0–0.06) and Gd_0.80-yTb_0.15Ce_0.05PO₄·H₂O:yLi⁺ (y = 0.01–0.06) phosphors have been successfully synthesized via hydrothermal method. The phase structure, morphology, elemental composition, surface absorption and luminescence properties of the samples were characterized by XRD, SEM, EDS, FT-IR and PL, respectively. The results show that all the synthesized samples are all pure hexagonal phase structure of GdPO₄·H₂O nanorods. The influence of Ce³⁺ and Li⁺ concentrations on the photoluminescence properties of the Li⁺ co-doped GdPO₄·H₂O:Tb³⁺,Ce³⁺ green phosphors have been thoroughly investigated. When Ce³⁺ and Li⁺ ions were co-doped into GdPO₄·H₂O:Tb³⁺, the excitation band red-shifted from 274 to 302 nm, and the emission intensity was enhanced up to approximately 30 times compared with that of Ce³⁺/Li⁺-free Gd_0.85Tb_0.15PO₄·H₂O because of the efficient energy transfer from Ce³⁺→Tb³⁺ in the GdPO₄·H₂O host. Moreover, the optimized Gd_0.76Tb_0.15Ce_0.05PO₄·H₂O:0.04Li⁺ phosphor has an internal quantum efficiency of 25.94 % and exhibits superior thermal stability (162.9 %@473 K). A new design strategy was proposed to enhance the crystallinity and luminescence intensity of GdPO₄·H₂O:Tb³⁺,Ce³⁺ green phosphor by inducing a flux or sensitizer through Li⁺ co-doping. These results indicate that the GdPO₄·H₂O:Tb³⁺,Ce³⁺,Li⁺ phosphor hold promising potential application as a UV-convertible phosphor for w-LEDs due to its wide excitation band in the ultraviolet region and effective generation of strong green emission.