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)TizO delta, 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 (Na0.92Li0.08)(Y0.8Gd0.2)TiO4:Eu3+ 31, the reproducibility of which was achieved by the conventional solid-state reaction method. Using the (Na0.92Li0.08)(Y0.8Gd0.2)TiO4:Eu3+ 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 Y2O2S:Eu3+ at an excitation of 400 nm.