High Thermoelectric Performance in n-Doped Silicon-Based Chalcogenide Si2Te3

Juneja, Rinlde and Pandey, Tribhuwan and Singh, Abhishek K (2017) High Thermoelectric Performance in n-Doped Silicon-Based Chalcogenide Si2Te3. In: CHEMISTRY OF MATERIALS, 29 (8). pp. 3723-3730.

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Abstract

Achieving large thermoelectric figure of merit in a low-cost material, having an appreciable degree of compatibility with the modern technology is required to convert waste heat into electrical energy efficiently. Using first principles density functional theory and semiclassical Boltzmann transport theory, we report high thermoelectric performance of a silicon-based chalcogenide Si2Te3. Previously unknown ground state structure of Si2Te3 was obtained by finding out the 8 most energetically favorable sites for Si in a unit cell of 12 Te and 8 Si atoms. Out of total C(28,8) combinations of structures, the search was narrowed down to 15 by using Wyckoff positions of space group P (3) over bar 1c. The minimum energy configuration having layered structure exhibits combination of desirable electronic and transport properties for an efficient thermoelectric material, including confinement of heavy and light bands near the band edges, large number of charge carrier pockets and low conductivity effective mass for n-type carriers. These features result into high thermopower and electrical conductivity leading to high power factor for n-type carriers. Furthermore, Si2Te3 possesses low frequency flat acoustical modes, which leads to low phonon group velocities and large negative Gruneisen parameters. These factors give rise to low lattice thermal conductivity below 2 W/mK at 1000 K. The combination of these excellent inherent electronic, transport and phononic properties renders an unprecedented ZT of 1.86 at 1000 K in n-doped Si2Te3, which is comparable to some of the best state-of-the-art thermoelectric materials. Our work presents an important advance in a long-standing search for the silicon-based thermoelectrics having exceptionally good energy conversion efficiency, and which could be integrated to the existing electronic devices.

Item Type:	Journal Article
Publication:	CHEMISTRY OF MATERIALS
Additional Information:	Copy right for this article belongs to the AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	03 Jun 2017 09:41
Last Modified:	03 Jun 2017 09:41
URI:	http://eprints.iisc.ac.in/id/eprint/57107

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