Interfacial Behavior of 2D Materials in Devices for Solar Fuels and Sensing Applications

Author: Thompson, Annelise C.

Year: 2019

Degree: Dissertation (Ph.D.)

Advisor: Lewis, Nathan Saul

Committee Members: Gray, Harry B.; See, Kimberly; Okumura, Mitchio; Lewis, Nathan Saul

Option: Chemistry

DOI: 10.7907/DQF7-JD96

Abstract

The field of 2D materials has expanded widely in the past 15 years to include many materials beyond graphene. However, the applications of graphene and its derivatives are still limited by the lack of thorough knowledge on how to successfully integrate a 2D material into a device while maintaining its unique properties. The work in this thesis investigates the application of 2D materials, such as graphene, fluorinated graphene, and hexagonal boron nitride, in solar fuels and sensing devices to reveal patterns that can inform device design with these and other materials in the future. In the second chapter, lightly fluorinated graphene is investigated as a protective layer on silicon photoanodes. This material is shown to possess superior abilities as a protective layer against oxidizing conditions as well as other deleterious surface reactions. The introduction of fluorine atoms to the lattice at postulated to terminate defects found along grain boundaries, leading to enhanced stability over 24h. The third chapter addresses the energetics of silicon/2D material/liquid junctions to elucidate how the density of states in these materials affect the formation of efficient charge-separation junctions. Hexagonal boron nitride on p-type silicon is shown to form a superior junction to graphene, as measured by changes in the open-circuit potential against a range of one-electron redox couples. Finally, chapter four shows the integration of a monolayer of graphene into a polymer-based chemiresistive vapor sensor to substantially enhance the signal of the sensor over the graphene or polymer alone. The response is dependent on strain at the graphene interface as demonstrated by Raman spectroscopy.

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