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.
Recommended Citation
Brehm, John A., "First-Principles Exploration of the Structural Motifs of Chalcogenides and Their Relationship to Electronic and Photovoltaic Properties" (2014). Publicly Accessible Penn Dissertations. 1214.
https://repository.upenn.edu/edissertations/1214