Tunable luminescence and energy transfer properties based on La₂O₃-P₂O₅:Dy³⁺/Tm³⁺ glasses

The white-LED material Dy³⁺/Tm³⁺ co-doped phosphate glass was prepared by a conventional melting method. The energy transfer in the two rare earth ions was supposed by changing the concentration of one doping ion and was further demonstrated by the fluorescence lifetime. The energy level transition mechanism between the rare earth ions was analyzed using the Inokuti–Hirayama theory. There were two kinds of energy transfer mechanisms from the dipole–quadrupole interaction (Dy³⁺ → Tm³⁺) and the quadrupole–quadrupole interaction (Tm³⁺→Dy³⁺). The luminescence color was tuned from a blue to a near standard white light emission using 350 nm excitation and adjusting the rare earth ion doping ratio. The results show that 15La₂O₃-85P₂O₅:xDy₂O₃-yTm₂O₃ glass is a promising UV-excited white photodiode material.