Synthesis of Stoichiometric Pyrite Photovoltaic Absorbers

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TECHNICAL SUMMARY:Two strategies will be pursued to produce phase-pure pyrite (beta-FeS2) in a thin film form. First, we will leverage our experience activating nanostructured hematite (alpha-Fe2O3) photoanodes for water splitting. Thermodynamics suggest that hematite can be directly transformed to pyrite, bypassing undesired phases that are encountered when using iron as a precursor. The second approach will employ pulsed plasma-enhanced chemical vapor deposition (PECVD), a cyclic technique that provides Angstrom-level control over film thickness. A key element is the use of plasma-assisted fabrication processes to provide enhanced S activity and precise control over exposure. The investigations will be informed by unique in situ diagnostic capabilities and comprehensive evaluation of material properties and device performance. In both cases pyrite will be formed in intimate contact with a conducting tin oxide/hematite structure that will allow interrogation of the opto-electronic performance, in addition to providing an advanced front contact that facilitates device fabrication. NON-TECHNICAL SUMMARY:New low cost, earth abundant solar cell technologies are required to generate the TW levels of power required for sustainability. Pyrite is the most promising semiconductor for solar energy conversion in terms of potential capacity and cost. It is a non-toxic, earth abundant compound that can very efficiently absorb light for photovoltaic applications. Single junction solar cells derived from this material are theoretically capable of 25% efficiency, but the best results obtained in the limited studies to date are 3%. The work described in this proposal will establish the scientific knowledge base required to successfully produce phase-pure pyrite in a thin film form required for photovoltaics. A major contribution of this project will be the education and advanced training of both graduate and undergraduate students in the materials science and advanced processing of inorganic thin film PV. The PI's group will continue their K-12 outreach work, developing workshop materials related to renewable energy for teachers in school districts with large populations of underrepresented students.This project is supported by the Solid State and Materials Chemistry program.