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Open Access Dissertation
Doctor of Philosophy (PhD)
Year Degree Awarded
Month Degree Awarded
Paul M. Lahti
E. Bryan Coughlin
Materials Chemistry | Organic Chemistry | Physical Chemistry | Polymer Chemistry
Designing and synthesizing materials for use in organic electronic materials requires fine control over their optical and electronic properties. Variations through substitution can be used to tune solubility and electronic properties, but this can result in degradation of other properties. Substitution with orthogonal pendant groups in both molecular and polymeric systems has the potential for allowing tunability while decreasing the perturbation of other desirable properties of the parent system.
This idea was explored through experimental and computational work. Computational modelling was used to understand and predict the properties of molecular and polymeric systems to narrow the wide number of choices of possible materials. The ability to computationally predict not just molecular orbital energy levels, but other properties of the system such as UV-Vis transitions, unpaired spin-density, and changes in dipole moment is important not just for designing new materials, but in understanding how they work. This is accomplished in modelling a modular approach to tuning of frontier orbital energy levels. Newer strategies for predicting photovoltaic performance by analysis of the ground-to-excited state dipole moment change are also explored.
A series of low-bandgap polymers absorbing at a bandgap of 1.7 eV, near the ``ideal'' bandgap of 1.5 eV, were prepared by copolymerizing an electron-donating and electron-withdrawing unit to yield a low-bandgap ``push-pull'' copolymer. The donor unit was designed to study the effect of pendant phenyl substitution. The resulting copolymers were oligomeric in nature, but devices prepared using these copolymers gave very promising photovoltaic power conversion efficiencies up to 5\%. The influence of a pendant phenyl unit in the copolymers yielded a system with increased order in the solid state, and decent performance.
Design and synthesis of new materials through pendant tuning was shown to be a viable strategy for developing new organic electronic materials, and methods to explore this for new materials were established.
Tinkham, Jonathan S., "Design and Application of Organic Electronic Materials: Pendant Tuning in Polymeric and Molecular Systems" (2015). Doctoral Dissertations. 412.