Electronic structure engineering of tin telluride through co-doping of bismuth and indium for high performance thermoelectrics: a synergistic effect leading to a record high room temperature ZT in tin telluride

Abstract

The ever increasing demand for alternative clean energy sources has led to intense research towards the optimization of thermoelectric performance of known systems. In this work, we engineer the electronic structure of SnTe by co-doping it with Bi and In. The co-doping not only results in the formation of two different resonance states and a reduced valence band offset, as in the case of previously reported co-doped SnTe, but also leads to opening of the band gap, which otherwise was closed in the case of Bi and In doped SnTe configurations, leading to suppression of bipolar diffusion. The synergistic action of all these effects leads to an increased Seebeck co-efficient throughout the temperature range and a ZT_max of ∼1.32 at 840 K. This strategy of co-doping two different resonant dopants resulted in a record high room temperature ZT of ∼0.25 at 300 K for SnTe based materials. This work suggests that appropriate combination of dopants to engineer the electronic structure of a material can lead to unpredictable results.