Characterizing and modeling of exciton dissociation in polythiophene
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Exciton dissociation, the separation of an electron and hole upon excitation by radiation, is studied in the conjugated polymer polythiophene (PT). Based on data from semi-empirical simulations of exciton dissociation in PT, a dissociation distance parameter and the radius of gyration are calculated for the excited state electron and hole for different chain lengths of polymers. These characteristics are studied in relationship to themselves and each other to glean insight into the process and details of dissociation. It is learned that after the exciton is created, the length of the polymer that it spans is dependent on the chain length of the polymer. Also, it is discovered that the exciton changes in size in a consistent fashion, creating a pulsating effect with a consistent pulsating frequency. In addition, a novel course-grained model for simulating exciton dissociation is created and implemented based solely on an effective interaction energy potential between the exciton cloud and the torsional angles between the rings of the polymer. The parameters for this model are chosen based off of the behavior seen in the semi-empirical calculations. After applying this new model to new configurations of the polythiophene polymer, the results are compared to results of the mixed quantum-classical simulations on the same configurations to show reasonably accurate prediction in the distribution of the exciton along the polymer.