Realizing bright blue-red color-tunable emissions from Gd2GeO5:Bi3+,Eu3+ phosphors through energy transfer toward light-emitting diodes

Novel Bi3+/Eu3+ ions co-doped Gd2GeO5 (GGO) phosphors were prepared by a high-temperature solid-state reaction method. X-ray diffraction, photoluminescence (PL), CIE chromaticity coordinates, internal quantum efficiency (IQE), and temperature-dependent PL spectra were applied to analyze the as-obtained phosphors. The emission spectra of the GGO:Bi3+,Eu3+ phosphors showed both a broad blue band of Bi3+ emission centered at 453 nm and the characteristic sharp red emission lines of Eu3+, corresponding to the 3P1→1S0 allowed transition of the Bi3+ ions and the 5D0→7FJ (J = 0, 1, 2, 3, 4) transitions of the Eu3+ ions, respectively. Notably, the as-prepared GGO:Bi3+,Eu3+ phosphors exhibited color-tunable emissions from blue (Bi3+) to red (Eu3+) with increasing the Eu3+ doping concentration via a high-efficiency energy transfer process. Moreover, the mechanism of energy transfer from Bi3+ to Eu3+ ions was determined to be the dipole-quadrupole interaction. Impressively, the optimal GGO:0.05Bi3+,0.12Eu3+ phosphors had an outstanding IQE as great as 88% and good thermal stability. All these meaningful results demonstrated that blue-red color-tunable GGO:Bi3+,Eu3+ phosphors have potential applications in white light-emitting diodes (LEDs) and plant growth LEDs.