Manipulation of Solubility and Interstitial Defects for Improving Thermoelectric SnTe Alloys

Much effort has recently been directed at advancing thermoelectric SnTe as an alternative to PbTe. Effective methods include energy band convergence, nanostructures, and substitutional and interstitial defects. Among these strategies, it is shown that CdTe alloying effectively reduces the energy offset between valence bands for an enhanced thermoelectric figure of merit, zT. However, its solubility of only ∼6% might limit this effect on a full zT optimization in SnTe–CdTe alloys. Here, we show an effective approach for increasing CdTe solubility up to ∼20%, with the help of the existence of 5% GeTe. This leads the valence bands to be further converged for improving electronic performance. In addition, Cu2Te alloying is used to create interstitial defects for reducing the lattice thermal conductivity. Eventually, the increase of CdTe solubility and the creation of Cu interstitials enable a significantly enhanced zT, indicating the importance of solubility manipulation for engineering the band structure in thermoelectric SnTe alloys.