Computational Evolutionary Optimization of Red Phosphor for Use in Tricolor White LEDs

An evolutionary optimization process involving a genetic algorithm and combinatorial chemistry was employed in an attempt to develop titanate-based red phosphors suitable for use in tricolor white light-emitting diodes. An eight-cation oxide system, including (K,Li,Na) x (Y,Gd,La,Eu) y Ti z O δ, was screened in terms of luminescence efficiency. The use of a combination of a genetic algorithm and combinatorial chemistry enhanced the efficiency of searching, as it is applied to the screening of phosphors in a limited composition space. As a result, the optimum composition was determined to be (Na 0.92 Li 0.08 )(Y 0.8 Gd 0.2 )TiO 4:Eu 3+, the reproducibility of which was achieved by the conventional solid-state reaction method. Using the (Na 0.92 Li 0.08 )(Y 0.8 Gd 0.2 )TiO 4:Eu 3+ phosphor and an InGaN chip, a red LED was realized, so that the applicability of this new phosphor to white LEDs was confirmed. The luminescence of this phosphor was 110% that of the well-known scheelite variant phosphor and 600% that of a commercially available Y 2 O 2 S:Eu 3+ at an excitation of 400 nm.