Relating morphology and optical response in conjugated polymers: insights from and into simulations
Abstract: Electronic and optoelectronic devices based on soft organic and biological polymers may change the way we maintain our environment, generate energy and treat otherwise incurable health conditions, for example, brain trauma. The rational design of such devices is hindered because the relationship between morphology and electronic and optoelectronic behaviors of conjugated or biological polymers is, in general, poorly understood. In this talk, (A) I will describe some of our recent insights into this complex relationship derived from simulations: We have demonstrated theoretically that torsional disorder in substituted polythiophenes can polarize the excited electron-hole pairs (excitons), and observed this effect directly using single-molecule spectroscopy experiments in a collaborative effort. Of particular practical interest is our finding that exciton polarization in conjugated polymers can be controlled with non-bonding interactions, for example, with strategically chosen side-chains; this insight may help manipulate the mechanism of exciton diffusion and charge-separation in organic photovoltaics; And (B) I will discuss a novel computational methodology based on a repurposed artificial intelligence algorithm that provides much needed additional means of interpretation for coarse-grained simulations of conjugated polymers. Specifically this method is able to predict the absorption spectra of poly-3-hexylthiophenes directly from coarse-grained representations by-passing the errors associated with the inevitably non-unique mappings back into atomistic coordinates.
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