Lead-free thermoelectrics: promising thermoelectric performance in p-type SnTe1-xSex system

Lead chalcogenides are the best performers for thermoelectric power generation at mid/high temperatures; however, environmental concern about Pb prevents its use in large-scale thermoelectric applications. SnTe, a Pb-free IV-VI narrow band gap semiconductor, has the potential to be a good thermoelectric material due to its crystal structure and valence band characteristics being similar to those of PbTe. Here, we report the promising thermoelectric performance in high quality crystalline ingots of In-doped SnTe1-xSex (x = 0-0.15) synthesized by a simple vacuum sealed tube melting reaction. First, we have optimized the lattice thermal conductivity of SnTe by solid solution alloying with SnSe. Resonance level formation in the valence band through In doping along with the increase in the contribution of the heavy hole valence band through solid solution alloying significantly improved the Seebeck coefficient, resulting in a promising ZT of similar to 0.8 at 860 K in the Pb-free p-type 1.5 mol% In doped SnTe0.85Se0.15 sample.