Structure and Dynamics at Organic Semiconductor Interfaces: The Influence of Molecular Electronic Structure

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With the support of this award from Chemical Structure, Dynamics and Mechanisms program in the Chemistry Division of the National Science Foundation, Professor Oliver Monti from the University of Arizona leads a team of scientists to investigate the critical factors that determine charge-transfer at interfaces of organic semiconductors. By choosing a class of related yet tunable organic semiconductor molecules on surfaces with well-defined properties, this research uniquely permits systematic control of the interface in order to extract the influence of the molecular and surface electronic structure on interfacial charge-transfer dynamics. Initial results show that easily accessible molecular properties such as the molecular dipole and quadrupole moment, together with the band structure of the surface, dictate in a predictive fashion the interfacial electronic structure both in ground and excited states. Research will establish how these properties determine the fate of electronic excitations at interfaces and will make it possible to unravel the underlying physics of interfacial charge-transfer in organic semiconductors. The highly controlled approach of the proposed experiments will advance understanding of charge-transfer processes to interfaces of extended pi-conjugated organic molecules with complex electronic structure and rich thin film growth properties. While interfacial charge-transfer is a crucial step in many chemical processes in general, it is central in novel solar energy conversion platforms and catalysis based on organic materials. The proposed research program will thus develop a deeper understanding of one of the fundamental driving forces in chemistry. With its focus on organic electronic materials it will aid in developing a scientific workforce both at the graduate and undergraduate level in the broader area of energy sciences, an area of critical national need. Findings from the proposed research will flow conceptually also into "Solar Wizards", a hands-on science show for children and their parents to discover the potential of sunlight as a power source and developed together with the local chapter of the Student Members of ACS (SMACS). "Solar Wizards" is anticipated to travel to "Solar Rock," a yearly multi-day community-based music festival in Tucson dedicated to alternative energy generation, and to after-school science programs in Native Nations schools on the outskirts of Tucson.