October 2007

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My work is currently dedicated to white LED (light-emitting diode) efficiency improvement to meet the industry goal of 150 lumens per watt. When commercialized these light sources will be 10 times more efficient than the energy-hungry incandescent lamps commonly used in interior spaces.

In 2005, I worked with my research group to propose a remote phosphor concept- known as SPE� (scattered photon extraction), which dramatically improved light output and luminous efficacy by 60%. In 2006, for my Masters Degree thesis project, I characterized the wavelength dependent optical properties of YAG: Ce phosphor and used these results in optical ray-tracing analysis to demonstrate improved accuracy of simulation. From my studies it became evident that the phosphor efficiency depends on the particle size. Therefore, nano-sized phosphors have potential to improve the luminous efficacy of white LEDs.

My recent study toward PhD is focused on understanding the behavior of both conventional micron-phosphors and advanced nano-phosphors and developing novel optical structures to minimize packaging induced light loss in order to improve luminous efficacy of white LEDs. I am hoping to optimize nano-phosphor particle size, excitation and emission wavelengths, and improve wetting properties of these materials when immersed in different binders and encapsulants. In addition I will analyze different phosphor placement concepts to maximize light extraction from white LEDs.

Mineral Carbon Dioxide Sequestration refers the disposal of the greenhouse gas C02 by its conversion to a solid carbonate mineral. The solid product is environmentally benign and stable for hundreds of millions of years. Furthermore, the mineral resources required as inputs to this process are abundant as to provide a limitless capacity for greenhouse gas disposal(Lackner 2002). These combined characteristics of limitless and permanent greenhouse gas disposal capacity in a form that is environmentally benign is unmatched in the suite of carbon mitigation technologies.

Currently the energy costs of this process are considered a factor 3 to 5 too high to be feasible for use as a greenhouse gas mitigation technology. This cost is in part driven by the speed of the multiple chemical reactions needed for the carbonation to occur. The focus of this dissertation is in the research of kinetic enhancements to the process through the use of catalysts and optimization of conditions for individual process steps. The achievement of relatively small kinetic enhancements in this process will have a profound effect on the economic viability of the technology and in turn on the strategies for greenhouse gas management in the immediate future.

I aim to reduce the cost per watt of solar power by developing technology based on 1) molecular semiconductors and 2) concentrator systems, which replace expensive solar cells with passive light redirection elements. Scalable, inexpensive systems to convert solar power provide a pathway to ubiquitous, clean energy.

Organic semiconductors are compatible with low cost manufacturing methods but current performance is lacking. I adapt the organization of processes in photosynthesis and introduce a synthetic light harvesting structure into organic semiconductor solar cells which couple to the active device area by near field energy transfer to increase power conversion efficiency. Spatially separating the optical and electrical components is a unique departure from existing photovoltaic technologies. External light absorbing structures are a general way to increase power conversion efficiencies in absorptionlimited solar cells.

Diffuse solar concentration is an inexpensive method to concentrate light that does not require solar tracking. The luminescent solar concentrator redirects and concentrates light absorbed over a large area through guided energy transfer via an optical waveguide. A small number of photovoltaic receive the concentrate, wavelength-converted light. Recent improvements in chromophores and photonic crystals provide a route towards high efficiency systems. By adapting and furthering these technologies, we can develop systems designed as direct replacements for residential rooftop solar panels.