The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.
This award will support a twenty-two-month research fellowship by Dr. Ryan C. White to work with Dr. Marco-Aurelio De Paoli at the University of Campinas in Brazil. Support for this project comes from the Office of International Science and Engineering's (OISE) Americas Program.
As the need for renewable energy resources grows, dye-sensitized solar cells (DSSCs) are emerging as a viable alternative to the traditional silicon cells developed and commercialized over 60 years ago. The most well known DSSC is the Gratzel cell which can reach an overall efficiency of ~10%. One major advance made in the production of this cell is the incorporation of high surface area mesoporous metal oxide materials. This increases the amount of dye molecules in contact the surface in for a given area. While these types of cells have proved the potential viability of these types of cells commercially, their fabrication proves difficult and expensive due to the reactive electrolyte needed, as well as expensive dye molecule precursors. In the Dr. De Paoli's laboratory, and others, conjugated polymeric materials have been used as the both photoactive dyes and electrolytes. These polymers have definite advantages over small molecules in cost and durability, while showing similar absorption characteristics of Gratzel cell dye molecules. To date the DSSC's containing polymeric dyes have had relatively low conversion efficiencies. The goal of this project is to develop polymeric dye materials with more efficient charge transport properties and to fabricate more efficient DSSCs. By covalently attaching the conjugated polymer film to the inorganic substrate, better orbital overlap is achieved and the rate of electron injection into the electrical circuit is increased. The identity of both the dye monomer and linker can be changed to optimize the injection process. To quantitatively study the electron injection properties, model compounds are synthesized of different inorganic nanoparticle-linker-dye combinations. This is accomplished by modifying conjugated monomers molecules such as thiophene with carboxylic or phosphonic acid groups which can anchor onto the metal oxide nanoparticle surface. Electron transfer rates of these compounds can be studied directly by time resolved laser flash photolysis absorbance and fluorescence techniques. To attach the polymeric dye to the inorganic layer, the conjugated dye monomers are attached to inorganic surfaces via anchoring groups and polymerized by chemical and electrochemical means. The photovoltaic responses and efficiencies of these novel types of DSSC's are analyzed by electrochemical instrumentation in Dr. De Paoli's laboratory.
