Date of Award

2014

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Chemistry

First Advisor

Joseph E. Subotnik

Abstract

The bulk photovoltaic effect (BPVE) refers to the production of electric currents from the

valence band promotion of electrons to the conduction band in a pure, undoped, and insulating

material from the absorption of electromagnetic radiation. For a material to be able to

create a current in response to non-polarized solar irradiation, it must be a polar compound

with a band gap in the visible spectrum, 1.1 - 3.1 eV. The purpose of this work is to provide

computational evidence that the pursuit of materials other than pure oxides for use as bulk

photovoltaic materials is worthy. To convince the scientific community that compounds

containing isoelectronic elements of O, the chalcogens S and Se, should be synthesized

and, as importantly, are capable of being synthesized, three distinct subject areas will be

presented. The first demonstrates that it is possible to alloy sulfur with an oxide perovskite,

lead titanate (PTO), to create thermodynamically stable polar oxysulfides with band gaps

in the visible spectrum. In the second, it will be shown that non-oxide non-perovskite

materials can generate BPVE responses larger by an order of magnitude over the oxide

perovskites listed in the literature to date. The third area does not address solar energy use

directly. Instead, it alerts the scientist that creating ABS3 compounds by using temperature

and time profiles used to synthesize ABO3 compounds has probably led to an incomplete

characterization of these sulfides. As such, it provides first-principles based evidence that

synthesis experimentation involving chalcogens does not and should not simply mirror that

of pure oxide synthesis. The scientific community's knowledge of chalcogenides is far from complete, opening up exciting possibilities for new material discoveries.

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