Electronic Structure of Conducting Polymers and Organic Materials

Georgetown University, Washington DC

Investigators

Abstract

This award is funded by the Materials Theory Program in the Division of Materials Research and the Theoretical and Computational Chemistry Program in the Chemistry Division. The objective of this project is to determine strategies and perform reliable calculations for predicting the fundamental properties of organic molecular semiconductors and organic conjugated polymers. While the proposed work relies heavily on first principles calculations, empirical elements in the computational modeling process are retained and emphasized. Intermolecular packing is difficult to predict from first principles, but packing directly effects intermolecular hopping, the key parameter to be studied in the first part of this project. The effect of intermolecular packing on the band structure of conjugated polymers, the subject of the second part of this project, is indirect often exerting its effect through torsional degrees of freedom. In either case, the integration of direct or indirect experimental information on packing or torsion ensures that the quality of the predictions is more reliable, than it would be in a purely first principles approach. The reliability of the predictions for the organic molecular materials is ensured via a multi-scale approach in which dimers play a central role. The dimer level splittings can be treated with very accurate quantum chemical methods, and the effect of a number of key influences will be studied systematically, including level of theory, basis set, and geometrical effects, which will be used to predict the electronic structure of these materials. For conjugated polymers, the approach contains similar elements, but the proposed work focuses on predicting small band-gap polymers. Several effects influence the band-gap, including connectivity, various geometrical factors including deviations from planarity and bond localization, and others that are more chemical in nature such as heteroatoms and side groups. Plans include method development for a polymer computer code, and applications across specific groups of polymers that have the potential of producing very small band-gaps. This research has the potential to significantly influence experimental studies by helping to search for new and better functioning materials for device applications. The project also involves students at the undergraduate and graduate level. %%% This award is funded by the Materials Theory Program in the Division of Materials Research and the Theoretical and Computational Chemistry Program in the Chemistry Division. The objective of this project is to determine strategies and perform reliable calculations for predicting the fundamental properties of organic molecular semiconductors and organic conjugated polymers. This research has the potential to significantly influence experimental studies by helping to search for new and better functioning materials for device applications. The project also involves students at the undergraduate and graduate level. ***