Georgia Institute of Technology Materials Science and Engineering

Committee Members: 

Prof. John R. Reynolds, Advisor, MSE/CHEM

Prof. Blair Brettmann, CHBE/MSE

Prof. Rampi Ramprasad, MSE

Prof. Natalie Stingelin, MSE/CHBE

Prof. Stefan France, CHEM

Exploring Charge Transport in Solution-Processable Conjugated Polymers

Abstract:

Due to their capacity for synthetic tuning and solution processability, conjugated polymers (CPs) enable the development of new electronic device architectures and technologies. Charge transport in solution-processable CPs is expounded in this talk, with an emphasis on the development of structure-property relationships to tune materials properties. Side chain and backbone structures of CPs are functional handles by which electron density and carrier localization are modified, with concomitant changes to the optical, thermal, and microstructural properties. Subtle changes in molecular structure additionally give rise to differences in device performance, allowing for the development of design rules for materials optimization. Structure-property relationships are explored for several applications (i.e., organic solar cells for energy generation, reversible redox materials for mixed ionic and electronic conduction, and materials for electrically conductive films in the solid-state) with each presenting a unique landscape for charge transport.  

In the first project, the effect of increasing side chain steric bulk of thienopyrroledione-based polymers will be discussed in relation to resultant optical, morphological, and thermal properties, as well as solar cell device statistics. In the second project, we investigate three new polar side chain substituted copolymers with varied dioxythiophene comonomers. Spectroscopic, electrochemical, and computational data allows us to gain insight into the effects of comonomer planarity on redox properties. Additionally, the polymers are studied for their suitability in aqueous electrochromic and model Type I supercapacitor devices. In our third project, the same copolymer series is studied, demonstrating how comonomer choice allows the electronic and thermoelectric properties of polymer films to be tuned. At optimal doping conditions, electrical conductivities of the polymer series span over two orders of magnitude, with the highest electrical conductivity approaching 200 S/cm. In the final project, various electrolyte anions are studied to probe how size, hydrophilicity, and relative “hardness” affect the swelling and redox cycling properties of a polar side chain functionalized dioxythiophene homopolymer.