zT factors in Ag- and Na-doped SnSe: Chemical potentials, relaxation times and predictions for other dopant species

The chemical potential μ and relaxation time τ of SnSe doped with Ag and Na have been investigated by a methodology that combines first-principles calculations with solutions of the Boltzmann transport equation under the relaxation time approximation. The best comparison with experimental data avail...

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Bibliographic Details
Published in:Journal of alloys and compounds 2018-08, Vol.757, p.70-78
Main Authors: Meléndez, Juan J., González-Romero, Robert L.
Format: Article
Language:English
Subjects:
Approximation
Boltzmann transport equation
Chemical potential
Dopants
Doping
Electric properties
First principles
Mathematical analysis
Organic chemistry
Relaxation time
Scattering
Semiconductor doping
SnSe
Temperature
Temperature dependence
Thermal conductivity
Thermoelectrical performance
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Summary:The chemical potential μ and relaxation time τ of SnSe doped with Ag and Na have been investigated by a methodology that combines first-principles calculations with solutions of the Boltzmann transport equation under the relaxation time approximation. The best comparison with experimental data available is obtained for temperature-dependent μ and τ in both cases. The chemical potential relative to the Fermi energy is found to be independent on the particular doping species, and similar to that of pure SnSe. The relaxation time shows the same trend in all cases at temperatures below 550 K, which suggests that the same scattering mechanism is active in the pure and doped systems. As for the thermal conductivity, the analysis of the experimental results reveals that it is the same for both dopants below roughly 550 K as well, but higher than that of pure SnSe. From these findings, estimations of zT values for other dopants, namely Ge and S, are made. The results indicate that doping with S yields very poor figures of merit while doping with Ge could yield better thermoelectrical performance than that reported for Na-doped SnSe. •The effect of Ag- and Na-doping on the transport coefficients of SnSe is studied.•Doping does not change the chemical potential relative to the Fermi energy.•The scattering mechanism for charge carriers seems to be unaffected by doping.•The thermal conductivity is also roughly unchanged by doping.•Higher zT factors could be found in Ge-SnSe; S-doping yields a poorer performance.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2018.05.042