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Optimum Carrier Concentration in n‐Type PbTe Thermoelectrics
Author(s) -
Pei Yanzhong,
Gibbs Zachary M.,
Gloskovskii Andrei,
Balke Benjamin,
Zeier Wolfgang G.,
Snyder G. Jeffrey
Publication year - 2014
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201400486
Subject(s) - materials science , doping , thermoelectric effect , effective mass (spring–mass system) , fermi level , condensed matter physics , thermoelectric materials , figure of merit , electronic band structure , electrical resistivity and conductivity , electron mobility , optoelectronics , x ray photoelectron spectroscopy , thermal conductivity , thermodynamics , electron , nuclear magnetic resonance , physics , quantum mechanics , composite material
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.