Probing multimodal light emission from Tb/Yb-doped garnet nanophosphors for lighting applications.

Herein we report the solution-combustion-method-synthesized Tb- and Tb/Yb-doped GdGaO nanophosphors, which possess luminescent and magnetic properties. The phase formation/crystal structure, and morphology of the prepared nanophosphors are studied using X-ray diffraction (XRD)/Raman spectroscopy and a field emission scanning electron microscope (FE-SEM), respectively. Tb/Yb-doped phosphor samples exhibit green emission with an intense band around 544 nm through downshifting (DS) and upconversion (UC) processes because of the D → F transition of Tb. In addition to this visible emission, these samples also show a NIR emission band around 1024 nm the quantum cutting (QC) process due to the F → F transition of Yb. Emission decay measurements of the D → F transition of Tb are performed to obtain the rate of energy transfer from Tb to nearby Yb. Furthermore, using this energy transfer, the quantum cutting efficiencies were estimated. For their practical application, a selected sample was used to fabricate a LED device by combining the sample with a UV-C LED (274 nm). The obtained results, such as the activation energy (∼0.20 eV) and the high CRI value (78), suggest that the prepared sample can be utilized as a green-light-emitting agent in phosphor-coated (pc) WLEDs.