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Low intensity conduction states in FeS2: implications for absorption, open-circuit voltage and surface recombination
Massachusetts Institute of Technology, Cambridge, USA.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-5571-0814
Massachusetts Institute of Technology, Cambridge, USA.
Massachusetts Institute of Technology, Cambridge, USA.
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2013 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 25, no 46, 465801- p.Article in journal (Refereed) Published
Abstract [en]

Pyrite (FeS2), being a promising material for future solar technologies, has so far exhibited in experiments an open-circuit voltage (OCV) of around 0.2 V, which is much lower than the frequently quoted 'accepted' value for the fundamental bandgap of similar to 0.95 eV. Absorption experiments show large subgap absorption, commonly attributed to defects or structural disorder. However, computations using density functional theory with a semi-local functional predict that the bottom of the conduction band consists of a very low intensity sulfur p-band that may be easily overlooked in experiments because of the high intensity onset that appears 0.5 eV higher in energy. The intensity of absorption into the sulfur p-band is found to be of the same magnitude as contributions from defects and disorder. Our findings suggest the need to re-examine the value of the fundamental bandgap of pyrite presently in use in the literature. If the contribution from the p-band has so far been overlooked, the substantially lowered bandgap would partly explain the discrepancy with the OCV. Furthermore, we show that more states appear on the surface within the low energy sulfur p-band, which suggests a mechanism of thermalization into those states that would further prevent extracting electrons at higher energy levels through the surface. Finally, we speculate on whether misidentified states at the conduction band onset may be present in other materials.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2013. Vol. 25, no 46, 465801- p.
Keyword [en]
Pyrite, FeS2, Band gap, Solid state, Surface, Condensed matter
National Category
Condensed Matter Physics
URN: urn:nbn:se:liu:diva-100153DOI: 10.1088/0953-8984/25/46/465801ISI: 000326674700021PubMedID: 24141033OAI: diva2:660453
Swedish Research Council, 621-2011-4249
Available from: 2013-10-29 Created: 2013-10-29 Last updated: 2013-12-09Bibliographically approved

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