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New phosphors for solid state white lighting


Solid state white lighting based on the direct conversion of electricity to light through the use of light emitting diodes, holds great promise for general lighting using. Such lighting offers completely non-toxic components, much cleaner production processes, significantly greater efficiencies, and longer lifetimes often by factors greater than 10. An important challenge in this area is the development of new phosphor materials that efficiently convert the blue light from an (In,Ga)N solid state light source to a full spectrum white light in an efficient manner.

ConvEne IGERT fellow Nathan George has been investigating phosphor materials for solid state white lighting for his graduate research. Jointly advised by Professor B. F. Chmelka (Chemical Engineering, UCSB) and Professor R. Seshadri (Materials, and Chemistry & Biochemistry, UCSB), Nathan has specifically been carrying out a careful study of the traditionally very successful garnet phosphor material Y3Al5O12:Ce, in order to determine the origin of its high efficiency and its impressive optical properties at elevated temperatures (required in applications such as vehicular headlamps) when other materials fail. His multi-pronged approach involves the use of synchrotron x-ray and neutron scattering, and high magnetic field magnetic resonance (NMR) studies, all of which have taken him to national labs in New Mexico, Florida etc. in order to acquire the most state-of-the-art data that yields information about subtleties in the structure of this material. In particular, the NMR studies suggest that the unpaired electron spin on Ce3+ in this compound can be used as an internal “shift reagent” for probing the coordination around the all-important Ce3+ sites in the crystal structure.

Address Goals

The work on the phosphors addresses an important national goal of developing materials for increased energy efficiency. In addition, Nathan is training in the use of advanced instrumentation and the national infrastructure.