<title>Combinatorial synthesis and screening of Cerium-doped garnet phosphors for application in white GaN-based LEDs</title>

Abstract

A combinatorial approach has been used to generate solid state thin-film of different garnet structures (A 1-x ,B x ) 3-z (C 1-y ,D y ) 5 O 12 :Ce 3+ z (called libraries), where A, B = Y, Gd, Lu, La; C, D = Al, Ga, Sc; x and y = 0 to 1.0; and z = 0.03. X-ray diffraction was used to select library samples of the crystalline garnet phase. Combinatorial chemistry methods were used as a tool to rapidly synthesize and screen potential inorganic phosphors for use as blue to yellow conversion phosphors in white LEDs. Libraries of these various garnets were then characterized spectroscopically. Emission and excitation trends are reported for various libraries and were found to reproduce previous trends in literature. Lattice constants, chromaticity, and PL intensity are also examined as a function of the different compositions. Emission and excitation trends reveal that as larger cations are substituted for the Y (dodecahedral) site in YAG, emission and excitation are red-shifted and as larger cations are substituted for the Al (octahedral and tetrahedral) site, emission and excitation are blue-shifted. If smaller ions are substituted for those respective sites an opposite trend is observed.

Method for the Detailed Characterization of Cosputtered Inorganic Luminescent Material Libraries

“…This lack of past works can be explained by that combinatorial methods, when applied to conventional searches like the search for white light LEDs, usually converge to known phosphors . In addition, the analysis methods used for combinatorially synthesized libraries of luminescent materials are often limited to (color-filtered) charge-coupled device (CCD) photography of a library under UV illumination, − substrate-scanning with color filters to isolate emission peaks, , or cathode luminescence with no information on low energy excitations . These coarse characterizations still have to be followed by powder synthesis to fully analyze the luminescent properties of a material of interest.…”