Multiple-Dye Fluorescent Microspheres and Films-A New Approach for Luminescent Solar Concentrators

9906282

Wittmershaus

This NSF-GOALI proposal provides support for an interdisciplinary research collaboration between Penn State Erie-The Behrend College and the scientists of Molecular Probes Inc. The PI's primary objective is to use TransFluoSpheres fluorescent microspheres and dyes manufactured by Molecular Probes Inc. in luminescent solar concentrators (LSCs) and assess their performance in converting sunlight to electricity. A LSC is a thin, flat plate of highly fluorescent material that uses total internal reflection to concentrate light at its edges where it is converted to electricity by semiconductor solar cell material. The main advantage of the LSC is its cost. It acts as a cheap, non-directional, area collector of light by focusing 75% of the photons it absorbs down to a very small area of expensive semiconductor material.

A LSC made with multiple-dye networks will absorb at least four times as many of the sun's photons as compared to traditional single-dye LSCs. The dye networks are constructed to optimize resonant excitation energy transfer among the dyes, minimizing losses associated with reabsorption of emission. Excitations created on the dyes hop among themselves until they end up on the lowest energy level dye molecules which then emit this energy as fluorescence within the LSC. The fluorescent microspheres are unique in that 95% of the excitations created in the dyes through the absorption of light are transferred to the low-energy level dye molecules. The spheres are 40-nm in diameter and contain six or more types of dyes resulting in an absorption spectrum that covers the entire visible region from 350 to 720 nm. They will also design and test LSCs composed of a thin-film of plastic containing multiple dyes at the proper relative concentrations to create an efficient excitation energy transfer network like the spheres.

They will incorporate the spheres and multiple-dye thin films into new designs for LSCs. Light concentration at the LSCs' edge will be measured using solar illumination and compared with published data for single-dye LSCs. The optical properties of the spheres and thin films will also be further characterized and modeled. Limits on the lifetime of the materials imposed by degradation under terrestrial light and temperature conditions will be assessed.

This work will be a significant change in the strategy of designing LSCs and lead to an expected factor of four improvement in their collection of light, ultimately giving a lower cost per kilowatt! They will increase their understanding of the optical characteristics of the spheres and determine the feasibility of using multiple-dye thin films to form efficient excitation energy transfer networks. This will lead to better assessments of the potential for using these materials in other optical applications, such as lasers, and may assist Molecular Probes in improving their fluorescent bioprobes.

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