SOLAR: Phase-Field Crystal Modeling and Analytical Surface Analysis of Iron Pyrite (FeS2) for Thin-Film Photovoltaics

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In this project funded by the Divisions of Chemistry, Materials Research, and Mathematical Sciences, Professors Matthew D. Law, John C. Hemminger, and John Lowengrub of the University of California-Irvine will study the use of iron pyrite in thin-film photovoltaics (PV). Pyrite or iron persulfide (FeS2) is an under-researched, extremely promising semiconductor for use as the light-absorbing layer. There are two key hurdles to utilizing this material for solar energy conversion: the difficulty in synthesizing high-quality, phase-pure pyrite and the low photovoltage of pyrite devices. This research will combine novel phase field crystal (PFC) and density functional theory (DFT) models with targeted synthetic and surface characterization efforts to grow device-quality pyrite thin films by sintering layers of solution-deposited pyrite nanocrystals and by chemical vapor deposition (CVD), and to fix the pyrite photovoltage by passivating mid-gap states via judicious annealing and coordination chemistry approaches. This collaboration between experts in continuum and atomistic crystal modeling (Prof. Lowengrub, Mathematics), pyrite growth (Prof. Law, Materials Science), and surface characterization (Prof. Hemminger, Chemistry) provides a new approach to developing semiconductor materials that are earth-abundant and environmentally friendly. Such properties are important for the large-scale implementation of solar energy as an alternative energy source. Undergraduate, graduate and postdoctoral researchers working in this team gain interdisciplinary perspectives not often encountered in standard academic curricula. To complement the research effort, the team is developing an intensive, month-long summer course on crystal growth for ~20 high school students annually as part of the California State Summer School for Mathematics and Science (COSMOS) at UCI. This course provides students with the opportunity to learn mathematical theory, use state-of-the-art simulation tools, and learn about crystallography and solar energy in the laboratory. The research team is also involved in the design and implementation of an interactive educational exhibit on solar energy and energy use, including real-time monitoring of an operating photovoltaic array, at the Discovery Science Center of Orange County. This site is expected to be visited by 70,000 K-12 students and 445,000 members of the community each year.