Investigation of multicolor emitting Cs3GdGe3O9:Bi3+,Eu3+ phosphors via energy transfer for WLEDs

Abstract

Bi³⁺/Eu³⁺ doped Cs₃GdGe₃O₉ luminescent materials were prepared by a solid-state reaction. The energy band and density of states of Cs₃GdGe₃O₉ were calculated by density functional theory. The Cs₃GdGe₃O₉ host presents a broadband emission peaking at 520 nm. Systemic measurement and analysis of luminescence properties were performed to confirm the energy transfer in Cs₃GdGe₃O₉:Bi³⁺,Eu³⁺. The multicolor modulated emission from blue (0.1678, 0.1568) to red (0.5931, 0.3251) can be achieved by varying the doping ratio of bismuth to europium. A white light-emitting diode (WLED) was produced by combining the Cs₃GdGe₃O₉:0.05Bi³⁺,0.1Eu³⁺ phosphor, a commercial green phosphor, and a 310 nm ultraviolet chip. The color rendering index of the WLED driven by 20 mA bias current is 89.6 with the CIE coordinates of (0.3520, 0.3626). The results reveal that the Cs₃GdGe₃O₉:Bi³⁺,Eu³⁺ phosphor is a potential material that can be used in multicolor tunable luminescence and WLEDs.