Date of Award

2018

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

Sub-Department

College of Arts and Sciences

First Advisor

Andrew B. Greytak

Abstract

Optoelectronic devices, such as solar cells and photodetectors, rely on separating and transporting charge through semiconductors that have excess electron-hole pairs created by photon absorption. This talk will focus of several different semiconductor materials of various dimensionality, such as lead halide perovskites, wide bandgap SiC, graphene, semiconductor nanowires (NWs), and quantum dots (QDs).

The results of Chapter 2 demonstrate the dependence of the perovskite/hole transport layer on carrier transport of perovskite films for solar cells. Efficient charge separation at the interfaces of the perovskite with the carrier transport layers is crucial for perovskite solar cells to achieve high power conversion efficiency. A systematic experimental study on the hole injection dynamics from MAPbI3 perovskite to three typical hole transport materials (HTMs) is discussed

Graphene layers grown epitaxially on SiC substrates are attractive for a variety of sensing and optoelectronic applications because the graphene acts as a transparent, conductive, and chemically responsive layer that is mated to a wide-bandgap semiconductor with large breakdown voltage. Recent advances in control of epitaxial growth and doping of SiC epilayers have increased the range of electronic device architectures that are accessible with this system. In particular, a recently introduced Schottky-emitter bipolar phototransistor (SEPT) based on an epitaxial graphene (EG) emitter grown on a p-SiC base epilayer has been found to exhibit a maximum common emitter current gain of 113 and a UV responsivity of 7.1 A W−1.

In Chapter 3, the sub- bandgap performance of the device is addressed, and a visible rejection ratio is calculated. Additionally, scanning photocurrent microscopy (SPCM) shows the localized effects of the photocurrent and the presence of an 8H- stacking fault. A new device fabricated with a thinner base region and SiF4 mediated EG growth process will be studied in Chapter 4. The spatial response of the photocurrent allows for determination of the visible rejection ratio, as well as a model of how generated carriers interact within the device.

Nanoscale optoelectronic devices of semiconductor CdS nanowires (NWs) and PbS quantum dots (QDs) are investigated in Chapter 5. The fabrication techniques, responsivities, on/off ratio, and spatial dependence of the devices will be discussed.

Available for download on Sunday, May 12, 2019

Included in

Chemistry Commons

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