Broad near-ultraviolet and blue excitation band induced dazzling red emissions in Eu3+-activated Gd2MoO6 phosphors for white light-emitting diodes

Abstract

A series of Eu³⁺-activated Gd₂MoO₆ phosphors were synthesized via a citric acid-assisted sol–gel route. The photoluminescence (PL) excitation spectra revealed that the obtained phosphors can be efficiently pumped by both near-ultraviolet and blue light. Upon 360 and 463 nm excitation, bright emissions corresponding to the ⁵D₀ → ⁷F_J (J = 0, 1, 2, 3 and 4) transitions of Eu³⁺ ions were detected. Meanwhile, the PL emission intensity was strongly dependent on the Eu³⁺ ion concentration and the optimal doping concentration for the Eu³⁺ ions in the Gd₂MoO₆ host lattice was determined to be around 15 mol%. The critical distance was around 11.47 Å and the mechanism for the concentration quenching was dominated by dipole–dipole interaction. Furthermore, the temperature-dependent PL emission spectra were recorded to test the thermal stability of the as-synthesized phosphors. Additionally, the Judd–Ofelt theory was employed to investigate the local crystal environment around the Eu³⁺ ions in the Eu³⁺-activated Gd₂MoO₆ phosphors. Finally, by integrating the resultant compounds with a blue light-emitting diode (LED) chip and yellow-emitting YAG:Ce³⁺ phosphors, a white light-emitting diode (WLED) device was fabricated which possessed a correlated color temperature of 5981 K, a color rendering index of 71.76 and a color coordinate of (0.321, 0.378). The results suggest that the Eu³⁺-activated Gd₂MoO₆ compounds are a promising red-emitting phosphor for WLEDs.