Reinforcing bond covalency for high thermoelectric performance in Cu3SbSe4-based thermoelectric material

Here, an effective strategy for weakening electron-phonon coupling to achieve high mobility is proposed and demonstrated to enhance the thermoelectric properties by increasing bond covalency in Cu3SbSe4-MTe (M = Ge/Sn) solid solution systems. We find that GeTe-alloyed Cu3SbSe4 samples possess a higher mobility at the similarly high carrier concentrations and thereby a larger power factor compared with the SnTe-alloyed system. Density function theory calculations suggest that GeTe-alloying facilitates the electrical transport improvement due to the weakening of electron-phonon coupling through increasing bond covalency. Consequently, a high thermoelectric figure of merit (ZT) ∼0.80 at 648 K and a competitive average ZT of 0.41 over 300–648 K can be achieved in 1% GeTe-alloyed Cu3SbSe4. Our study provides a new route of increasing bond covalency to enhance mobility for better thermoelectric materials.