Electron mean-free-path filtering in Dirac material for improved thermoelectric performance
Recent advancements in thermoelectric materials have largely benefited from various approaches, including band engineering and defect optimization, among which the nanostructuring technique presents a promising way to improve the thermoelectric figure of merit (zT) by means of reducing the character...
| Main Authors: | , , , , , , |
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| Format: | Article |
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National Academy of Sciences (U.S.)
2018
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| Online Access: | http://hdl.handle.net/1721.1/118460 https://orcid.org/0000-0002-1157-8540 https://orcid.org/0000-0002-9872-5688 https://orcid.org/0000-0002-7055-6368 https://orcid.org/0000-0002-2612-7750 https://orcid.org/0000-0002-1090-4068 https://orcid.org/0000-0002-8803-1017 |
| Summary: | Recent advancements in thermoelectric materials have largely benefited from various approaches, including band engineering and defect optimization, among which the nanostructuring technique presents a promising way to improve the thermoelectric figure of merit (zT) by means of reducing the characteristic length of the nanostructure, which relies on the belief that phonons’ mean free paths (MFPs) are typically much longer than electrons’. Pushing the nanostructure sizes down to the length scale dictated by electron MFPs, however, has hitherto been overlooked as it inevitably sacrifices electrical conduction. Here we report through ab initio simulations that Dirac material can overcome this limitation. The monotonically decreasing trend of the electron MFP allows filtering of long-MFP electrons that are detrimental to the Seebeck coefficient, leading to a dramatically enhanced power factor. Using SnTe as a material platform, we uncover this MFP filtering effect as arising from its unique nonparabolic Dirac band dispersion. Room-temperature zT can be enhanced by nearly a factor of 3 if one designs nanostructures with grain sizes of ∼10 nm. Our work broadens the scope of the nanostructuring approach for improving the thermoelectric performance, especially for materials with topologically nontrivial electronic dynamics. Keywords: Dirac material; electrom mean-free-path filtering; thermoelectrics; nanostructuring approach; electron-phonon interactions |
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