Low Intensity Conduction States in FeS₂: Implications for Absorption, Open-Circuit Voltage and Surface Recombination
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 ∼0.95 eV. Absorption experiments show l...
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IOP Publishing
2018
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| Online Access: | http://hdl.handle.net/1721.1/118360 https://orcid.org/0000-0002-6833-3480 https://orcid.org/0000-0002-7043-5048 https://orcid.org/0000-0001-8345-4937 https://orcid.org/0000-0002-2688-5666 |
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| author | Armiento, R Chan, M K Y Lazic, Predrag Herbert, Francis William Sun, Ruoshi Chakraborty, Rupak Buonassisi, Anthony Yildiz, Bilge Ceder, Gerbrand Hartman, Katy |
| author2 | Massachusetts Institute of Technology. Department of Materials Science and Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Materials Science and Engineering Armiento, R Chan, M K Y Lazic, Predrag Herbert, Francis William Sun, Ruoshi Chakraborty, Rupak Buonassisi, Anthony Yildiz, Bilge Ceder, Gerbrand Hartman, Katy |
| author_sort | Armiento, R |
| collection | MIT |
| description | 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 ∼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. |
| first_indexed | 2024-09-23T07:59:51Z |
| format | Article |
| id | mit-1721.1/118360 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T07:59:51Z |
| publishDate | 2018 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | mit-1721.1/1183602023-02-26T02:17:22Z Low Intensity Conduction States in FeS₂: Implications for Absorption, Open-Circuit Voltage and Surface Recombination Armiento, R Chan, M K Y Lazic, Predrag Herbert, Francis William Sun, Ruoshi Chakraborty, Rupak Buonassisi, Anthony Yildiz, Bilge Ceder, Gerbrand Hartman, Katy Massachusetts Institute of Technology. Department of Materials Science and Engineering Massachusetts Institute of Technology. Department of Mechanical Engineering Massachusetts Institute of Technology. Department of Nuclear Science and Engineering Lazic, Predrag Herbert, Francis William Sun, Ruoshi Chakraborty, Rupak Hartman, Katherine Buonassisi, Anthony Yildiz, Bilge Ceder, Gerbrand 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 ∼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. 2018-10-04T18:52:30Z 2018-10-04T18:52:30Z 2013-10 2013-04 2018-09-24T12:59:58Z Article http://purl.org/eprint/type/JournalArticle 0953-8984 1361-648X http://hdl.handle.net/1721.1/118360 Lazić, P et al. “Low Intensity Conduction States in FeS₂: Implications for Absorption, Open-Circuit Voltage and Surface Recombination.” Journal of Physics: Condensed Matter 25, 46 (October 2013): 465801 © 2013 IOP Publishing Ltd https://orcid.org/0000-0002-6833-3480 https://orcid.org/0000-0002-7043-5048 https://orcid.org/0000-0001-8345-4937 https://orcid.org/0000-0002-2688-5666 http://dx.doi.org/10.1088/0953-8984/25/46/465801 Journal of Physics: Condensed Matter Creative Commons Attribution 3.0 Unported license http://creativecommons.org/licenses/by/3.0/ application/pdf IOP Publishing IOP Publishing |
| spellingShingle | Armiento, R Chan, M K Y Lazic, Predrag Herbert, Francis William Sun, Ruoshi Chakraborty, Rupak Buonassisi, Anthony Yildiz, Bilge Ceder, Gerbrand Hartman, Katy Low Intensity Conduction States in FeS₂: Implications for Absorption, Open-Circuit Voltage and Surface Recombination |
| title | Low Intensity Conduction States in FeS₂: Implications for Absorption, Open-Circuit Voltage and Surface Recombination |
| title_full | Low Intensity Conduction States in FeS₂: Implications for Absorption, Open-Circuit Voltage and Surface Recombination |
| title_fullStr | Low Intensity Conduction States in FeS₂: Implications for Absorption, Open-Circuit Voltage and Surface Recombination |
| title_full_unstemmed | Low Intensity Conduction States in FeS₂: Implications for Absorption, Open-Circuit Voltage and Surface Recombination |
| title_short | Low Intensity Conduction States in FeS₂: Implications for Absorption, Open-Circuit Voltage and Surface Recombination |
| title_sort | low intensity conduction states in fes₂ implications for absorption open circuit voltage and surface recombination |
| url | http://hdl.handle.net/1721.1/118360 https://orcid.org/0000-0002-6833-3480 https://orcid.org/0000-0002-7043-5048 https://orcid.org/0000-0001-8345-4937 https://orcid.org/0000-0002-2688-5666 |
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