Molecular Photonic Materials

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In this project funded by the Chemical Structure, Dynamic & Mechanism B Program of the Chemistry Division, Professor Gerald Meyer of the Department of Chemistry at The University of North Carolina - Chapel Hill will develop new classes of molecular materials with interesting optoelectronic properties. The goal of this research is to understand the fundamental nature of interactions between light-absorbing, redox-active molecules anchored to metal oxide surfaces. Optimization of desired interactions will enable applications for the conversion of sunlight to electrical power. The project required inorganic and materials synthesis as well as solar cell fabrication that is well suited to the education of scientists at all levels. This group is also well-positioned to provide the highest level of education and training for students underrepresented in science. Outreach activities for K-12 students involving presentations at the local library and Science Center will also be part of the funded project. Transition metal polypyridyl complexes display a rich array of photophysical and electron transfer properties when anchored to oxide surfaces. The proposed studies focus on lateral intermolecular electron- and energy-transfer self-exchange reactions that provide a molecular basis for the transport of charge or energy across the oxide surface. The redox activity will be exploited as a new class of 'hole-transport' materials for application in solar cells. A newly developed time-resolved polarization anisotropy technique will be exploited to characterize lateral charge transfer reactions that may occur after excited state injection into wide band gap semiconducting oxides such as TiO2. These studies will be complimented by thermal electron transfer studies and modelling through Monte Carlo simulations. A fundamental goal is to establish how molecular structure influences the lateral self-exchange rate constants. Particular attention will be placed on Cu(II/I) and Co(II/I) self-exchange reactions that involve transfer of an electron and a ligand, behavior that may result in what has been termed structurally 'gated' electron transfer. The Marcus cross-relation will be tested to elucidate whether lateral electron transfer reactions that involve chemical change can be accurately predicted with the measured self-exchange rate constants.