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THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING
GEORGIA INSTITUTE OF TECHNOLOGY
Under the provisions of the regulations for the degree
DOCTOR OF PHILOSOPHY
on Friday, August 21, 2020
10:00 AM
via
BlueJeans Video Conferencing
https://gatech.bluejeans.com/977238789
will be held the
DISSERTATION DEFENSE
for
Augustus William Lang
"Electrochromic Devices Incorporating Conjugated Polymers and Cellulose: New Opportunities for Organic Electronics"
Committee Members:
Prof. John R. Reynolds, Advisor, CHEM, MSE
Prof. Lars Berglund, FPT (KTH)
Prof. Robert J. Moon, MSE, FPL
Prof. Elsa Reichmanis, CHBE/MSE
Prof. Natalie Stingelin, MSE/CHBE
Abstract:
Electrochromic devices (ECDs) offer on-demand light modulation for use in dimmable windows, mirrors, eyewear, and printed color-changing displays. Conventionally, these devices have been constructed using glass or petroleum-derived-plastics as substrates which comprise the majority of the overall device mass. Considering the environmental burden of the processing and disposal of these materials, this dissertation explores the use of renewable alternatives for the next generation of printable electrochromic devices based on redox-active conjugated polymers.
In order to render cellulose-based materials sufficiently conductive, thin films of poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) were studied using a mild acid post treatment to generate a 103-fold enhancement in solid-state conductivity. In studying the redox properties of acid-treated PEDOT:PSS films, the emergence of a low-oxidation-onset redox couple was observed along an expansion of the conductive potential window, making this material ideal for supporting the redox switching of electrochromic polymers (ECPs). These PEDOT:PSS films were then studied on transparent wood substrates developed in Prof. Lars Berglund’s group at KTH where lab-scale window-type electrochromic devices. Inkjet-printed PEDOT:PSS was also demonstrated as a means to pattern lateral, color-neutral electrodes onto nanocellulose-coated paper. Switching kinetics of these lateral devices assessed by video analysis showed moving front electrochromic switching was dictated by the ionic conductivity of the electrolyte rather than by the relatively large 460 Ω sq-1 surface resistance.
Finally, this lateral device format was utilized to study the photochemical degradation of ECDs encapsulated by renewable barrier films. These multilayer barrier films developed in Prof. Carson Meredith’s lab were composed of cellulose nanocrystals (CNCs) and chitin nanofibers (ChNFs). ECDs encapsulated these renewable barrier films were found to degrade at a similar rate compared to poly(ethylene terephthalate) (PET) and a PET-Al2O3 barriers. The photodegradation was found to proceed more rapidly when the ECP was set in its oxidized state prior to irradiation despite less evidence of photochemical oxidation by X-ray photoelectron spectroscopy.
In sum, this work demonstrates the potential for cellulose-based, printed electrochromic devices capable of achieving practical device lifetimes. Future studies aimed at better understanding photostability and moisture tolerance promise to enable a number of applications in disposable sensors, labels, and packaging based on these materials for ECDs.
