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Research

Research

Research

Summary

Pyrite is a potentially attractive and sustainable semiconductor for photovoltaic (PV) applications because of its low cost, abundance in the earth's crust, environmentally benign source material, and desirable electronic properties, such as 0.95 eV bandgap, high optical absorption coefficient, ease of n/p doping, high carrier mobility, and relatively long carrier lifetime; however, there has been only limited progress in producing high-quality pyrite thin films needed to explore the potential of this material for solar PV applications. The overall goal of the proposed research is to develop a fundamental understanding of the electronic and defect properties of doped and undoped pyrite thin films for solar photovoltaics.

The Pis will develop a fundamental understanding of the thermodynamic and kinetic factors involved in producing high-quality epitaxial pyrite thin films, and determine how growth conditions influence the structural, chemical, electrical, and optical properties of the films. Furthermore, methods will be developed to produce high-quality pyrite thin-films with controlled n- and p-type doping, high carrier mobility, and long diffusion length that are useful for PV applications. Towards this end, a Molecular Beam Epitaxy (MBE) process will be developed to enable film growth at high sulfur pressures, insuring that high quality pyrite films can be produced. A wide range of structural, chemical and electrical measurements, defect studies, and band-structure calculations will be used to characterize and analyze film properties. Growth studies will measure the sticking coefficient and resonance time of the impinging S and Fe as a function of temperature and reactant impingement rate, and the decomposition rate of pyrite will be measured in vacuum and under growth conditions. These experiments will be used to determine the rate-limiting steps for the forward and reverse reactions and, their influence on achieving high quality epitaxial pyrite films.

The proposed activities are designed to educate and inspire K-12 and graduate students in solar PV topics. First, a hands-on education module on solar PV technology will be developed and then presented to over 10,000 Arizona K-12 students through the Arizona State University (ASU) Science is Fun program. The module involves having students configure solar cells with various light sources to power an electronic device. The module will be delivered to K-12 classrooms by at least 15 undergraduate interns that are trained by the ASU LeRoy Eyring Center for Solid State Science. At least one third of the students that participate in the Science is Fun program will come from underrepresented groups. Second, for each year of the project, two high-school students will participate in the ASU Southwest Center for Education and the Natural Environment (SCENE) high?school program, where they will spend ten hours each week for a term in the Pis laboratory to develop a science-fair project involving the synthesis and characterization of pyrite materials for energy generation applications. Finally, graduate students will be trained in the fundamental aspects of PV technology and in the synthesis and characterization of thin films needed to be successful in the solar PV workforce.

Funding

National Science Foundation Division of Chemical, Bioengineering, Environmental, and Transport Systems

Timeline

September 2011 — August 2014