Effect of Te and In Co-doping on Thermoelectric Properties of Cu2SnSe3 Compounds

Recently, Cu2SnSe3-based compounds, as a new environment-friendly thermoelectric material, have attracted worldwide attentions. However, the pristine Cu2SnSe3 compound possesses relatively low carrier concentration and thus an inferior electronic transport properties. To optimize the thermoelectric properties of Cu2SnSe3-based compounds, herein, two series of Cu2SnSe3-xTex (x=0-0.2) and Cu2Sn1-yInySe2.9Te0.1 (y=0.005-0.03) samples were synthesized through traditional melting-annealing technique combined with plasma activated sintering (PAS). The role of Te and In co-doping on the thermoelectric properties of Cu2SnSe3-based compounds were systematically investigated. The solubility limit of Te in the Cu2SnSe3-xTex compounds is around 0.10. The substitution of Te on Se site significantly increases the effective mass of charge carrier from 0.2m(e) for pristine Cu2SnSe3 compound to 0.45m(e) for Cu2SnSe2.9Te0.1 compound, which improves the power factor of the material. Cu2SnSe2.99Te0.01 compound attains the maximum power factor of 1.37 mu W.cm(-1).K-2 at 300 K. To further improve the electronic transport properties of the material, Cu2SnSe2.9Te0.1 was chosen as the matrix and In was selected to dope on Sn site. We found that doping with In significantly improves the carrier concentration of Cu2SnSe3-based compounds from 5.96x10(18) cm(-3) for Cu2SnSe2.9Te0.1 to 2.06x10(20) cm(-3) for Cu2Sn0.975In0.025Se2.9Te0.1, which promotes the participation of multiple valence bands in the electronic transport. All these produce the great enhancements on the electrical conductivity, effective mass of charge carriers and power factor. As a result, Cu2Sn0.995In0.005Se2.9Te0.1 compound obtains the maximum power factor of 5.69 mu W.cm(-1).K-2 at 473 K. Due to the significant improvement of electrical transport performance and the decrease in lattice thermal conductivity, the maximum ZT of 0.4 is achieved for Cu2Sn0.985In0.025Se2.9Te0.1 compound at 773 K, which is 4 times higher than that of pristine Cu2SnSe3 compound.