Enhanced thermoelectric performance of Cs doped BiCuSeO prepared through eco-friendly flux synthesis

The synthesis of BiCuSeO oxyselenides by a flux method in air has been investigated. A maximum power factor of 230 μWm−1K−2 and a very low thermal conductivity of 0.42 Wm−1K−1 were obtained, leading to a high ZT value of 0.37 at 680 K for pristine BiCuSeO. With Cs doping, a large enhancement in electrical conductivity coupled with a moderate decrease in Seebeck coefficient lead to a power factor of 340 μWm−1K−2 at 680 K. In addition, Cs doping reduced the thermal conductivity further to 0.35 Wm−1K−1 at 680 K. The combination of higher power factor and reduced thermal conductivity results in a high ZT value of 0.66 at 680 K for Bi0.995Cs0.005CuSeO.