Strong enhancement of roomerature thermoelectric properties of Cu-doped Bi₂Te_2.7Se_0.3

We investigate thermoelectric properties of Cu-doped Bi2Te2.7Se0.3 fabricated using a simple doping process and spark plasma sintering. Through precise control of Cu doping, it is found that Cu atoms preferentially occupied Bi sites and then intercalated into the van der Waals gap with an increasing Cu content. Electrical transport properties of Cu-doped samples were systemically controlled using this mechanism. At the same time, thermal conductivities of the Cu-doped samples were reduced by the enhancement of point defect phonon scattering due to the Cu atoms. Compared to that of pristine samples, the dimensionless thermoelectric figure of merit ("ZT") of 0.98 at 323 K for the Cu-doped sample was increased by more than 92% owing to these synergetic effects. Furthermore, the shift of maximum ZT to room temperature provides advantages for enlarging the applications of thermoelectric effects at room temperature.