Energy transfer and color-tunable emission in trivalent terbium/europium doped multi-component borosilicate glasses for white light-emitting diodes under ultraviolet excitation

Multi-component sodium borosilicate glasses incorporated with trivalent terbium and europium ions in single and dual combinations via melt-quench technique were synthesized. Glasses doped with terbium and europium displayed intense green and red colors, respectively. The addition of various contents of europium ions to a pre -optimized content of 1.0 mol% terbium resulted in efficient energy transfer. The process of energy transfer was analyzed by studying the overlap of emission and absorption spectra, luminescence properties, the decay of donor (terbium) emissions, the energy level scheme and energy transfer parameters (eta and P) in the terbium/ europium codoped glasses. Emission spectra and lifetimes of terbium (sensitizer) are decreased with the rise of europium content at 351 nm excitation due to sensitization of europium by terbium. The energy transfer between these ions is analyzed through Dexter's theoretical model, Reisfeld's approximation, and Inokuti-Hirayama models, which confirm that the non-radiative energy transfer from terbium to europium is predominantly governed by dipole-dipole interaction. The chromaticity coordinates are presented to comprehend the color tenability from green to red via yellow due to the co-doping of terbium to europium, to confer the suitability of this combination for achieving solid-state/ indoor lighting applications.