Enhancement in thermoelectric performance of single step synthesized Mg doped Cu2Se: An experimental and theoretical study

Copper selenide (Cu2Se) is a simple binary compound which exhibits very fascinating thermoelectric properties, due to which it has been widely studied till very recently. This work highlights that the doping in Cu2Se only affect the electronic transport while the thermal transport is not significantly influenced due to the liquid like dynamics of the Cu ions in the lattice that results in significant thermal instabilities to an extent that the effect of doping is negligible. Our experiments show that an enhanced ZT similar to 1.6 at 860 K was achieved in Mg-doped Cu2Se, synthesized employing a facile single-step reactive spark plasma sintering technique, which is both fast and scalable. The experimental results indicate that Mg-doping in Cu2Se leads to a significant enhancement in its electrical conductivity, which is primarily responsible for the significant improvement in the ZT. However, the lattice thermal conductivity was found to remain relatively unchanged, irrespective of the Mg-doping concentration, which is also in agreement with our DFT calculations.