Comparison of influence of intercalation and substitution of Cu on electrical and thermoelectric transport properties of InSe alloys.

Layered post-transition-metal chalcogenides, such as InSe, In 4 Se 3 , SnSe, and SnSe 2 , have recently been investigated as semiconducting electronic materials and thermoelectric materials owing to their adjustable electrical transport properties either by doping or alloying. Herein, the influence of intercalation doping and substitutional doping of Cu in layered InSe alloys on electrical and thermoelectric transport properties was investigated and compared by synthesizing varied compositions of Cu x InSe and In 1- y Cu y Se. It was found that Cu was intercalated in Cu x InSe samples ( x = 0.01 and 0.02) and behaved as an electron donor, resulting in an increase in the electron concentration and a decrease in the activation energy. Therefore, the power factor of Cu x InSe samples was increased compared to that of InSe. In contrast, the substituted Cu in the In site of In 1- y Cu y Se samples ( y = 0.01 and 0.02) acted as an acceptor, and the power factor decreased owing to a decrease in the electron concentration and activation energy. Moreover, a decrease in thermal conductivity was seen for Cu x InSe and In 1- y Cu y Se samples due to increased phonon scattering after the addition of Cu. Consequently, an enhanced thermoelectric figure of merit ( zT ) was only observed for intercalated Cu x InSe samples due to the increased power factor and decreased thermal conductivity, while substituted In 1- y Cu y Se samples only show degraded zT . A maximum zT value of 0.062 was observed for the Cu x InSe ( x = 0.02) sample at 700 K, which showed a 77% enhancement compared to that of InSe.