Electronic structure and thermoelectric properties of In4Se3−x (x = 0, 0.25, 0.5, 0.75): First-principles calculations

•Se vacancy affects strongly on the thermoelectric properties of In4Se3−x.•Destroy degree of In–Se bonding determine the electrical behavior of In4Se2.75.•The semiconducting In4Se2.75 has a higher Seebeck coefficient than metallic ones.

Experimentally synthesized n-type In4Se3−x has a high thermoelectric figure of merit (ZT). The effect of Se vacancy on the electronic and thermoelectric properties of In4Se3 has been investigated by first-principles calculations. We find that the position and concentration of Se vacancy affect strongly on the thermoelectric properties of In4Se3. For In4Se2.75, three possible positions of Se vacancy lead to one type structure is semiconductor and other two structures are semimetal. Moreover, the semiconductor-type In4Se2.75 has a larger Seebeck coefficient than the semimetal type ones. The calculated low density of states near the Fermi level of the semimetal-type In4Se2.75 means that their metallicity is not so strong, which is helpful to their Seebeck coefficient. For In4Se2.75, the destroy degree of the In–Se bonding that plays a key role in determining whether the systems are metallic or semiconducting.