College of Science and Health Theses and Dissertations

Date of Award

Spring 6-14-2024

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

First Advisor

Graham Griffin, PhD

Second Advisor

Timothy French, PhD

Third Advisor

Kyle Grice, PhD

Abstract

A non-atomistic representation of the conjugated polymer PDBD-T-2F was constructed to model exciton delocalization and transport in the material. A Hamiltonian was built in the site basis to model the energy transfer, using excitation energies calculated using density functional theory and inter-site through-space coupling values calculated with either density functional theory or the newly integrated line-dipole approximation. The Hamiltonian allowed calculation of the excitation energies available for each system, prediction of the absorption spectrum, and simulation of the dynamics of exciton transport. For realistic crystal sizes at room temperature, the model predicts a band gap at 1.9 eV with decreasing absorption toward higher energies. This aligns with the absorption peaks in the experimental spectrum for PDBD-T-2F solvated in 1,2-dichlorobenzene as reported by Kroh et al. Exciton propagation through time illustrated the expected anisotropic, J-aggregate behavior. Delocalization in the pi-stacking direction was greater than the delocalization along either the intra-lamellar or the down-chain directions of the model. As a logistic benefit, the low-computation cost of this model enables at-will comparison between experimental results and simulated coupling behavior for closely packed systems with extended conjugation.

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