Superior thermoelectric performance in non-stoichiometric Cu3SbSe4 system: Towards synergistic optimization of carrier and phonon transport

Abstract

To investigate the effect of cation disorders to modulate thermoelectric performance of Cu3SbSe4 system, we attempted to tune copper content in Cu3+xSbSe4 (x = -0.06, -0.04, 0, 0.04, 0.06, and 0.08) system synthesized via solid-state reaction route. Considering the asymmetry in charge and phonon transport properties, intentional deviations from the proper stoichiometry successfully enhance the electrical transport and reduce the phonon transport simultaneously. The self-doping effect induced by the off stoichiometry in Cu3SbSe4 provides acceptor levels, thereby elevating the electrical conductivity. Modulating the Fermi level within the valence band, we could realize a power factor to the highest value of ∼232 µW/mK2 for the sample with x = -0.06 at 210 K. Considerable reduction in thermal conductivity is the key factor in enhancing the figure of merit to a maximum value of ∼0.033 (at 350 K) for the sample with x = 0.06, which about three times higher than that of the pristine sample. The present study demonstrates that non-stoichiometry plays a substantial role in modulating the thermoelectric transport of the Cu3SbSe4 system.