Date of Award
5-2026
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
School
Mathematics and Natural Sciences
Committee Chair
Song Guo
Committee Chair School
Mathematics and Natural Sciences
Committee Member 2
Xiaodan Gu
Committee Member 2 School
Polymer Science and Engineering
Committee Member 3
Wujian Miao
Committee Member 3 School
Mathematics and Natural Sciences
Committee Member 4
Vijay Rangachari
Committee Member 4 School
Mathematics and Natural Sciences
Committee Member 5
Karl Wallace
Committee Member 5 School
Mathematics and Natural Sciences
Abstract
Conjugated polymers (CPs) combine the mechanical flexibility of polymers with the optoelectronic properties of semiconductors, enabling their use in photovoltaic devices, organic electrochemical transistors, and wearable electronics. This work aims to gain a better understanding of doping at the local-scale and alternative patterning techniques for Conjugated polymers.
First, it was demonstrated that aggregate morphology provides spatial selectivity in electrophoretic deposition (EPD) of CPs. By exposing P3HT nanowires and nanoparticles to identical EPD conditions, two distinct deposition modes were observed: direct deposition onto the electrodes and deposition within the interelectrode gap. UV-Vis spectroscopy and atomic force microscopy (AFM) reveal differences in packing structure and morphology that underlie the distinct deposition behaviors, establishing aggregate morphology as a new approach for patterning CPs via EPD.
P3HT nanowires were further employed as a platform for probing doping at the local scale using Kelvin probe force microscopy (KPFM). Low dopant concentrations were used to directly compare doped and non-doped nanowires in the same image. By correlating topographical and surface potential changes it was found that doping effects do not propagate along the nanowire indicating that the doping effects are highly localized. Additionally, this work demonstrates the importance of dopant solvent orthogonality: while a non-orthogonal solvent leads to a greater extent of doping, it also changes the morphology of the CP aggregates. Furthermore, it is shown that the orthogonal solvent coats the CP in dopant, whereas the non-orthogonal solvents allows for intercalation.
Finally, this work introduces an electrically driven, material agnostic de-doping process which can be coupled with dopant-induced solubility control (DISC) patterning. Unlike prior approaches, which have relied on optical de-doping mechanisms that are limited to specific CP/dopant pairs, this bias-driven method demonstrated here is broadly applicable. Furthermore, it is shown to be reversible: by flipping the applied bias the doping state can be switched. Replicating the de-doping process in both solvent and open-air environments demonstrates that electrostatic dopant ejection alone cannot account for the overserved de-doping phenomenon, implicating a redox driven process. Fluorescence microscopy confirms the viability and spatial selectivity of this approach, extending DISC-based patterning to a wider range of CP/dopant systems.
ORCID ID
0009-0006-5803-1100
Copyright
Nicholas Kreis, 2026
Recommended Citation
Kreis, Nicholas, "Impact of Aggregation and Electrical Bias on the Doping and Deposition Behavior of P3HT" (2026). Dissertations. 2478.
https://aquila.usm.edu/dissertations/2478