Strategy to probe multimodal light emissions from Eu3+/Yb3+ activated garnet nanophosphors for LED devices and solar cell applications

Abstract

This study investigates multimodal light emission from an Eu³⁺/Yb³⁺ activated Y₃Ga₅O₁₂ (YGG) nanophosphor synthesized using a low temperature solution combustion method. The prepared sample possesses a cubic phase and an Iad space group and this is confirmed with X-ray diffraction and Rietveld refinement analysis. The synthesized sample shows orange-red emission bands because of the f–f transitions of Eu³⁺ under UV (393 nm) and NIR (980 nm) excitations via downshifting (DS) and upconversion (UC) processes, respectively. Upon UV (393 nm) excitation of the sample, the Eu³⁺ ions absorb this energy and then transfer it to a neighboring pair of Yb³⁺ ions giving NIR emission (900–1100 nm) corresponding to the ²F_5/2 → ²F_7/2 transition of Yb³⁺. The energy transfer from a single Eu³⁺ ion to a pair of Yb³⁺ ions is possible because of the quantum cutting (QC) process and this energy transfer efficiency is found to increase with the increasing concentration of the Yb³⁺. The quantitative estimation of energy transfer and internal quantum cutting efficiency is determined by measuring the decay kinetics. An activation energy of 0.25 eV indicates the good thermal stability of the sample. Furthermore, samples are suitable for use in practical applications in lighting devices by combining them with the near-ultraviolet (NUV; InGaN) chip. The fabricated LED device shows stability with the driving current flow values. Studies indicate that the present nanophosphor could be useful for display devices, and in enhancing the spectral conversion efficiency of the solar cells.