Combinatorial chemistry approach to searching phosphors for white light-emitting diodes in (Gd-Y-Bi-Eu)VO4 quaternary system
A red phosphor is desired to improve the color rendering index (Ra) of white light-emitting diodes (LEDs). Instead of developing a novel red phosphor individually, this work exploits a special yellow phosphor that contains red and green components to be matched with blue phosphor to produce white light. The desired emission color of yellow phosphor is tuned up by tailoring the green emission of Bi3+ and the red emission of Eu3+, and the luminescence efficiency and the thermal stability of luminescence are maximized by optimizing the composition of the host in the GdVO4-YVO4 system. A dynamic and virtual variation of samples emission color and intensity with Bi3+, Eu3+, Y3+ and Gd3+ concentrations and excitation wavelengths is clearly displayed in the luminescence images of the combinatorial libraries. The production of white light with high color rendering is demonstrated by preparing a practical white LED with a Ra of up to 90 from commercially available blue phosphor and optimized yellow phosphor.