Enhancement of thermoelectric performance by tuning selenium content in the Cu2SnSe3 compound

To investigate the thermoelectric properties, we have attempted to tune selenium content in Cu2SnSe3-delta (-0.04 <= delta <= 0.1) compounds synthesized via the conventional solid-state reaction. Electrical and thermal properties are presented in the low and near room temperature regime (10-350 K). The lowest electrical resistivity is observed for the compound with delta = 0.08. The electron-phonon coupling and the presence of small polarons are experimentally validated from temperature-dependent electrical and thermal transport data. A decrease in the Seebeck coefficient along with carrier concentration is observed, verifying the linear electron band dispersion. A downward shift of the Fermi level deep into the valence band is realized in the case of non-stoichiometric samples, thereby reducing the Seebeck coefficient. A maximum power factor of similar to 50 mu WmK(-2) is achieved for the sample with delta = 0.04, which is about twice that of the pristine compound. The highest ZT of similar to 0.01 is obtained for the compound with delta = 0.08. The observed results suggest that stoichiometry plays a vital role in tuning the thermoelectric properties in the Cu2SnSe3 compound.