Georgia Institute of Technology Materials Science and Engineering

Committee Members:

Prof. Natalie Stingelin, Advisor, MSE/ChBE

Prof. Elsa Reichmanis, ChBE

Prof. Carlos Silva, CHEM

Prof. Mark Losego, MSE

Prof. Nazanin Bassiri-Gharb, ME

"Elucidating the Effect of Local Polar Environment on Organic Semiconductors via Blending"

Abstract:

Ferroelectric polymers are widely exploited in sensors, energy storage applications, and memory devices, due to their spontaneous polarization, permanent dipole moments and high dielectric constants. However, their use in fields such as microelectronics and organic optoelectronics is limited due to their insulating properties. On the other hand, organic semiconductors, which are prevalent in electronic applications, are, in many instances, limited in efficiency owing to their low dielectric constants. Blending of these polymers by solution processing, has the potential to combine these multifarious, rare set of functionalities, ferroelectricity and conductivity. This proposal outlines the fundamental insights gained from such semiconducting:ferroelectric polymer blends and their proposed impact.

The first aim of this research is to deliver a detailed picture of the optoelectronic landscape of polymer semiconductors in polar, ferroelectric surroundings, by analyzing the optical properties and charge dynamics of the blends using ultrafast spectroscopy. We selected as a model system, a commodity ferroelectric polymer poly(vinylidene difluoride) (PVDF), and the archetypal semiconducting polymer poly(3-hexylthiophene-2,5-diyl) (P3HT), with the aim to combine these set of properties. The next aim is to gain further insights into semiconducting:ferroelectric polymer blends when processing them from solution while offering tunability of the structural and optical features of the blends. The final aim presented in this proposal is to make use of the novel set of functionalities, conductivity and ferroelectricity, in a materials blend system, by implementing these blends in optoelectronic devices, such as photovoltaics or memory devices.

The overall aim of this research is to deliver fundamental insights of the interplay between the structural, optical and electronic landscape of multicomponent functional polymer systems. By understanding the relation between microstructure, phase morphology, and the macroscopic dielectric and ferroelectric properties of solution-crystallized polymer blend films, the overall goal of this thesis is to disentangle their structural and optoelectronic influence on device performance. Lastly, we aim to establish and understand relevant structure/property/performance relations and provide a platform to design new multicomponent materials systems with multifunctional architectures that can open pathways for new devices and technology platforms.