Nanoscale Assemblies for Solar Energy: Transition metal-derived polymers and polypeptides for thin film solar energy production

Principal Investigators: Tom Meyer, Marcey Waters, Valerie Ashby, Garegin Papoian, John Papanikolas
Chemistry

Given the increasingly important challenges posed by energy supply and environmental impact, there is an increasing need to find solutions to the nation's and world's energy needs based on renewable energy. Solar energy utilization is central to this strategy. Semiconductor solar devices continue to evolve but there is potential for technological breakthrough based on less expensive organic thin film devices and molecular assemblies for solar fuel production. Significant progress has been made in both areas but both are near the beginning of their technology maturation curves, requiring significant fundamental research if they are to progress.

A powerful approach to both exists based on designed molecular assemblies. Their utilization necessitates flexible synthetic strategies and the ability to design and prepare multi-component assemblies in controlled spatial arrays. The key functional elements are efficient, long-range electron and energy transfer, interfacial electron transfer, and coupling of single photon, single electron transfer events to multiple electron reactions such as the half reactions of water splitting into hydrogen and oxygen.

This research in the Department of Chemistry, sponsored by the UNC Solar Energy Initiative(UNC-SEI), combines investigation of the assembly properties of polymers and polypeptides, note the structures below, with the optical and redox properties of transition metal complexes to develop new functional nanoscale materials. Their fundamental photophysical and energy and electron transfer properties are being investigated. The goal is to investigate their use for light-harvesting, long-range energy and electron transport and redox separation as a basis for new photovoltaic devices and for the photocatalytic production of high energy chemicals such as water splitting into hydrogen and oxygen.

Figure 1: Chemical structures of polymer arrays. The open circles represent other coordination complexes that are not shown for clarity.

Figure 2. Calculated Structure of Ru-derivatized polystyrene from Monte Carlo simulations.

This effort includes a number of research strengths and participating faculty: inorganic synthesis, characterization, and electrochemistry, organic synthesis and characterization of bioinspired assemblies, polymer synthesis and analysis, modeling of complex systems, and photophysics of transition metal complexes and multichromophoric assemblies.