Tunable photoemission and energy transfer of heavily Bi3+,Eu3+ co-doped Y4GeO8 phosphors

Co-doping activators is an effective way to obtain flexible light source by manipulating the energy transfer between dopants. Herein, heavily Bi3+,Eu3+ co-doped Y4GeO8 polycrystalline with tuned visible photoluminescence were prepared by using solid-state reaction method. Systematical characterizations on crystal structure and optical properties were conducted via X-ray diffraction patterns, fluorescence spectra, fluorescence decay curves, temperature-dependent spectra and quantum efficiency. Results show that the doping concentration of Bi3+ reaches up to 6.25%. Under ultraviolet excitation, a tunable emission covering green, yellow and red region of visible light was observed on account of the co-absorption and Bi3+→Eu3+ energy transfer. Especially, the sample Y4GeO8:0.25Bi3+,0.65Eu3+ presents excellent red emission with external quantum efficiency of 37.4% and quenching temperature of 443 K. Our results reveal that Y4GeO8:Bi3+,Eu3+ phosphors could be promising candidates for white light emitting diodes under ultraviolet excitation. •Y4GeO8:Bi3+,Eu3+ red phosphors were successfully designed and elaborated.•Heavy doping of Bi3+ ions with content of 6.25% was realized.•Tunable emission was achieved by tuning excitation scheme and the content of Bi3+ and Eu3+.•The optimized sample presents high EQE of 37.4% and good thermal stability.