Study of YAG : Ce and Polymer Composite Properties for Application in LED Devices.

The cost of the rare-earth metal cerium means that preparation of YAG : Ce is expensive. To overcome this, the garnet could partially be replaced by cheaper alternatives, while retaining the original properties of YAG : Ce. Composites with different polymers such as polyethylene glycol diacrylate (M280) and dipentaerythrityl hexaacrylate (M600) were therefore studied. YAG : Ce and boron nitride were added into the polymer matrix in order to obtain composites with enhanced thermal conductivity, necessary for high-optical-density applications. The physical properties of the composites were measured by using XRD, DSC, SEM, and NMR, and the most important characteristics for LED materials such as emission, excitation, decay time and quantum efficiency were analyzed. An LED prototype was developed to test and demonstrate the composites for practical applications. That developed device exhibited optical properties very close to those comprising a commercial garnet prototype, which was also developed for comparison. The main advantage of the proposed technology is that by using 2 time less the amount of YAG : Ce, almost the same light output was obtained compared to commercial phosphors.