The effect of the polymeric matrix on the emission properties of YAG-based phosphors

Abstract In the present paper we have studied the possibility to obtain nanocomposites by embedding yttrium aluminum garnet doped with Ce3+ and Gd3+ (YAG:Ce,Gd) phosphor in different polymer matrices, polydimethylsiloxane (PDMS), poly(methyl methacrylate) (PMMA) and epoxy resin (RE), for deposition on blue chips with the applicable purpose of generating white light. In order to obtain the nanocomposites, the ex-situ method which is based on the formation of a homogeneous mixture between phosphor and the polymeric matrix was chosen. YAG:Ce,Gd phosphor is previously dispersed in a suitable solvent for increasing the degree of compatibility with the polymer matrix. The device obtained to demonstrate the possibility of using the composites in white light emission, consists of a printed circuit containing pads on which 12 blue chips can be mounted. After welding the chips and connecting them using gold wire, YAG:Ce,Gd-based nanocomposites were injected and a thermal treatment was performed for cross-linking the composite at temperatures below 120 °C. The maximum temperature is imposed by the functionality parameters of a blue chip. The developed materials were analyzed from a morphological, structural and optical point of view using FTIR spectrometry, X-ray diffraction, AFM microscopy and photoluminescence spectrometry as characterization techniques. The quality of the light emitted was studied from the photometric point of view, finding an improvement of the CRI parameter compared to a commercial white LED. The chromaticity coordinates were studied and a "warm white" light was found for the RE-YAG:Ce,Gd and "cold white" composite for the PDMS-YAG:Ce,Gd and PMMA-YAG:Ce,Gd composites.