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Published September 14, 2014 | public
Journal Article

Optimum Carrier Concentration in n-Type PbTe Thermoelectrics

Abstract

Taking La- and I-doped PbTe as an example, the current work shows the effects of optimizing the thermoelectric figure of merit, zT, by controlling the doping level. The high doping effectiveness allows the carrier concentration to be precisely designed and prepared to control the Fermi level. In addition to the Fermi energy tuning, La-doping modifies the conduction band, leading to an increase in the density of states effective mass that is confirmed by transport, infrared reflectance and hard X-ray photoelectron spectroscopy measurements. Taking such a band structure modification effect into account, the electrical transport properties can then be well-described by a self-consistent single non-parabolic Kane band model that yields an approximate (m*T)^(1.5) dependence of the optimal carrier concentration for a peak power factor in both doping cases. Such a simple temperature dependence also provides an effective approximation of carrier concentration for a peak zT and helps to explain, the effects of other strategies such as lowering the lattice thermal conductivity by nanostructuring or alloying in n-PbTe, which demonstrates a practical guide for fully optimizing thermoelectric materials in the entire temperature range. The principles used here should be equally applicable to other thermoelectric materials.

Additional Information

© 2014 WILEY-VCH Verlag GmbH & Co. Received: March 20, 2014. Revised: April 8, 2014. Published online: May 7, 2014. Y.P. acknowledges the Recruitment Program of Global Experts (1000 Plan) of China, the program for professor of special appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning, Pujiang project of Shanghai Science and Technology Commission (13PJ1408400) and the Bayer-Tongji Eco-Construction & Material Academy (TB20140001) for funding support. G.J.S. acknowledges NASA-JPL and DARPA Nano Materials Program for funding support. Z.M.G. would like to acknowledge the Molecular Materials Research Lab (MMRC) at Caltech for use of instruments for optical data in this work. W.G.Z. is a recipient of a fellowship from the Carl Zeiss-Stiftung and acknowledges financial support through the Excellence Initiative (DFG/GSC 266). The HAXPES instrument at beam line P09 is jointly operated by the University of Würzburg (R. Claessen), the University of Mainz (C. Felser), and DESY. Funding by the Federal Ministry of Education and Research (BMBF) under Contract Nos. 05KS7UM1, 05K10UMA, 05KS7WW3, and 05K10WW1 was gratefully acknowledged. This article was modified after initial online publication to correct errors in the byline and affiliation. In the original version, Andrei Gloskovskii appeared in the affiliation section, but was inadvertently omitted from the byline. The affiliation for Benjamin Balke has also been corrected.

Additional details

Created:
August 20, 2023
Modified:
October 18, 2023