Modulation of the Electronic Structure and Phonon Transport of SnTe for High Thermoelectric Performance
Lead chalcogenides are the best performers for thermoelectric power generation at mid-high temperatures; however, environmental concern about Pb limits its use in large-scale thermoelectric applications. SnTe, a IV-VI narrow band gap semiconductor, can be an alternative of PbTe due to its similar crystal structure and valence band characteristics.1 The journey of SnTe, as a potential thermoelectric material begins with In doped SnTe where In creates resonance level. This has been further optimized via lattice thermal conductivity reduction in SnTe1-xSex.2 Another constraint of SnTe is the large energy separation between the light and heavy hole valence bands which restricts the contribution of heavy hole mass to the Seebeck coefficient. Doping of Mg and Ag in SnTe significantly tunes the electronic structure of SnTe, which decreases energy difference between the light hole and heavy hole valence bands, leading to enhanced Seebeck coefficient and thermoelectric efficiency.3,4 Co-doping of the In and Ag in SnTe yields synergistic enhancement in Seebeck coefficient and power factor over a broad temperature range because of the introduction of resonance state and convergence of valence bands.1 Moreover, pristine SnTe exhibits κlat of ~2.88 Wm-1K-1 at room temperature, while theoretical limit for minimum lattice thermal conductivity (κmin) is ~0.5 Wm-1K-1. We have successfully reduced lattice thermal conductivity of SnTe near to its theoretical minimum limit, κmin, via Sb alloying which spontaneous form nanodomains of Sb-rich layered intergrowth SnmSb2nTe3n+m compounds.5
1. Banik, A.; Shenoy, U. S.; Waghmare, U. V.; Biswas, K. J. Am. Chem. Soc. 2016, 138, 13068.
2. Banik, A.; Biswas, K. J. Mater. Chem. A 2014, 2, 9620-9625.
3. Banik, A.; Shenoy, U. S.; Anand, S.; Waghmare, U. V.; Biswas, K. Chem. Mater. 2015, 27, 581.
4. Banik, A.; Biswas, K. J. Solid State Chem. 2016, 242, 43.
5. Banik, A.; Vishal, B.; Perumal, S.; Datta, R.; Biswas, K. Energy Environ. Sci. 2016, 9, 2011-2019.