Towards a new chalcopyrite high-performance thermoelectric semiconductor Cu3InSnSe5 by entropy engineering

A new semiconductor Cu3InSnSe5 is introduced by entropy driven alloying equimolar ratio CuInSe2 and Cu2SnSe3. Cu3InSnSe5 is a p-type semiconductor (Eg ∼0.41 eV) and crystallizes in the chalcopyrite structure with I4_2 m space group. Our density functional theory calculations show that Cu3InSnSe5 exhibits an electronic band structure with multiple valance band peaks, rendering a large density of state effective mass m* of 1.8 me. Therefore, Cu3InSnSe5 has a high power factor of 7.59 μW cm−1 K−2 at 773 K. In addition, Cu3InSnSe5 also has a low lattice thermal conductivity (0.34 W m−1 K−1 at 773 K) owing to its severe lattice distortion arose by entropy enhancement. As a result, the figure of merit reaches as high as 1.08 at 773 K for Cu3InSnSe5. Furthermore, electronic band engineering is adopted to enhance the carrier concentration and m* of Cu3InSnSe5 via the substitution of In for Sn, resulting in ∼28% enhancement in power factor, ∼21% increment in ZT (1.31 at 773 K), and ∼10% enhancement in average ZT (∼ 0.67 at 473 – 773 K) for Cu3In1.01Sn0.99Se5 compared with Cu3InSnSe5 itself. Our work shows Cu3InSnSe5 should be a promising candidate for thermoelectric power generation at medium temperature.