TY - JOUR
T1 - Convergence of electronic bands for high performance bulk thermoelectrics
AU - Pei, Yanzhong
AU - Shi, Xiaoya
AU - Lalonde, Aaron
AU - Wang, Heng
AU - Chen, Lidong
AU - Snyder, G. Jeffrey
N1 - Funding Information:
Acknowledgements This work was supported by NASA-JPL and the DARPA Nano Materials programme; the work at SIC-CAS was supported by CAS. We thank J.-P. Fleurial, S. Bux, D. Zoltan and F. Harris for measurements of transport properties at NASA’s Jet Propulsion Laboratory and at ZT Plus Inc.
PY - 2011/5/5
Y1 - 2011/5/5
N2 - Thermoelectric generators, which directly convert heat into electricity, have long been relegated to use in space-based or other niche applications, but are now being actively considered for a variety of practical waste heat recovery systems-such as the conversion of car exhaust heat into electricity. Although these devices can be very reliable and compact, the thermoelectric materials themselves are relatively inefficient: to facilitate widespread application, it will be desirable to identify or develop materials that have an intensive thermoelectric materials figure of merit, zT, above 1.5 (ref. 1). Many different concepts have been used in the search for new materials with high thermoelectric efficiency, such as the use of nanostructuring to reduce phonon thermal conductivity, which has led to the investigation of a variety of complex material systems. In this vein, it is well known that a high valley degeneracy (typically Currency sign6 for known thermoelectrics) in the electronic bands is conducive to high zT, and this in turn has stimulated attempts to engineer such degeneracy by adopting low-dimensional nanostructures. Here we demonstrate that it is possible to direct the convergence of many valleys in a bulk material by tuning the doping and composition. By this route, we achieve a convergence of at least 12 valleys in doped PbTe 1-&permil-x Se x alloys, leading to an extraordinary zT value of 1.8 at about 850-‰kelvin. Band engineering to converge the valence (or conduction) bands to achieve high valley degeneracy should be a general strategy in the search for and improvement of bulk thermoelectric materials, because it simultaneously leads to a high Seebeck coefficient and high electrical conductivity.
AB - Thermoelectric generators, which directly convert heat into electricity, have long been relegated to use in space-based or other niche applications, but are now being actively considered for a variety of practical waste heat recovery systems-such as the conversion of car exhaust heat into electricity. Although these devices can be very reliable and compact, the thermoelectric materials themselves are relatively inefficient: to facilitate widespread application, it will be desirable to identify or develop materials that have an intensive thermoelectric materials figure of merit, zT, above 1.5 (ref. 1). Many different concepts have been used in the search for new materials with high thermoelectric efficiency, such as the use of nanostructuring to reduce phonon thermal conductivity, which has led to the investigation of a variety of complex material systems. In this vein, it is well known that a high valley degeneracy (typically Currency sign6 for known thermoelectrics) in the electronic bands is conducive to high zT, and this in turn has stimulated attempts to engineer such degeneracy by adopting low-dimensional nanostructures. Here we demonstrate that it is possible to direct the convergence of many valleys in a bulk material by tuning the doping and composition. By this route, we achieve a convergence of at least 12 valleys in doped PbTe 1-&permil-x Se x alloys, leading to an extraordinary zT value of 1.8 at about 850-‰kelvin. Band engineering to converge the valence (or conduction) bands to achieve high valley degeneracy should be a general strategy in the search for and improvement of bulk thermoelectric materials, because it simultaneously leads to a high Seebeck coefficient and high electrical conductivity.
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U2 - 10.1038/nature09996
DO - 10.1038/nature09996
M3 - Article
C2 - 21544143
AN - SCOPUS:79955610065
VL - 473
SP - 66
EP - 69
JO - Nature
JF - Nature
SN - 0028-0836
IS - 7345
ER -