Theory and simulations of electronic processes in organic semiconductors

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This project concerns theoretical and numerical simulations of charge and energy transfer processes in organic semiconducting systems. Two major project components are focused upon the role of specific nuclear motions and a "mode projection" technique that allows to reduce a high-dimensional quantum dynamics calculation to one involving only a few specific "collective" modes. The goal is to understand how such collective modes come into play in light-harvesting systems and charge-transfer systems. In effect, these modes provide a rigorous and molecular level description of the "reaction coordinate." A third component concerns predicting the properties of exciton polariton states in organic molecular crystals and self-assembled organic semiconducting polymer systems. Of particular interest is the possibility of polariton Bose condensate states in these systems. Such condensates have been observed in GaAs microcavities but, thus far, not in organic microcavities.The "mode projection" technique can be applied in a wide range of cases beyond electron-phonon systems and, thus, offer an avenue for efficient algorithms in electronic structure theory or electronic transport theory. The systems addressed in the project are of interest for molecular electronic devices. The work on polariton BEC, while certainly risky, holds considerable promise for broad impact since such states have not been observed to date in organic semicondicting microcavities. The theory and simulations in these systems provide much needed guidance for experimental efforts in this direction. Certainly, the broadest impact is in the training of PhD students and postdoctoral researchers involved in this project. This award is funded by the Theory Models and Computational Methods program of the Chemistry Division.