Multi-cations compound Cu2CoSnS4: DFT calculating, band engineering and thermoelectric performance regulation

The existence of multiple converged valence bands and low sound velocity are found in Cu2CoSnS4. Cu/M co-substitution for Cobalt is guided to improve its thermoelectric properties. Ultimately, an unprecedented high ZT of 0.8 at 800 K had been achieved due to the improved electrical properties from enhanced effective mass and the depressed lattice thermal conductivity by weakening of covalent-bonding.286