Neophytou, Neophytos, Zianni, Xanthippi, Kosina, Hans, Frabboni, Stefano, Lorenzi, Bruno and Narducci, Dario (2014) Power factor enhancement by inhomogeneous distribution of dopants in two-phase nanocrystalline systems. Journal of Electronic Materials, Volume 43 (Number 6). pp. 1896-1904. doi:10.1007/s11664-013-2898-z ISSN 0361-5235.

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Abstract

In this work, we describe a novel idea that allows for high thermoelectric power factors in two-phase materials that are heavily doped with an inhomogeneous distribution of dopants. We show that a concurrent increase of the electrical conductivity and Seebeck coefficient and a consequent increase of the power factor can be achieved in such systems. To explain the concept, we employ a semiclassical one-dimensional model that considers both electron and phonon transport through a series connection of two-phases of the material. We discuss microscopic characteristics of the material and the formation of the two phases (grains and grain boundaries in our case) by the inhomogeneous distribution of dopants in the polycrystalline material. Our theoretical investigation reveals that: (1) the improvement in the Seebeck coefficient can be attributed to carrier filtering due to the energy barriers at the grain boundaries, and to the difference in the lattice thermal conductivity of the grains and grain boundaries, and (2) the improvement in the electrical conductivity is a result of a high Fermi level in the grains. This allows high energy carriers to contribute to transport, which increases the impurity scattering limited mean-free-path, and increases the conductivity in the grains and thus in the whole material. Such an unexpected concurrent increase of the electrical conductivity and the Seebeck coefficient was recently observed in heavily boron-doped polycrystalline silicon of grain sizes <100 nm in which a silicon-boride phase is formed around the grain boundaries. We provide a simple 1D model that explains the behavior of this system, indicating processes that can take place in heavily doped nanocrystalline materials.

Item Type:	Journal Article
Divisions:	Faculty of Science, Engineering and Medicine > Engineering > Engineering
Journal or Publication Title:	Journal of Electronic Materials
Publisher:	Springer New York LLC
ISSN:	0361-5235
Official Date:	June 2014
Dates:	Date Event June 2014 Published 26 November 2013 Available 29 October 2013 Accepted 12 July 2013 Submitted
Volume:	Volume 43
Number:	Number 6
Page Range:	pp. 1896-1904
DOI:	10.1007/s11664-013-2898-z
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access (Creative Commons)

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