Boosting thermoelectric performance of BiCuSeO by improving carrier mobility through light element doping and introducing nanostructures

BiCuSeO oxyselenides are promising thermoelectric materials because of their high stability and high thermoelectric performance. Here, a new approach is proposed that Li and Ca are incorporated into BiCuSeO to achieve synergistically optimized electrical and thermal transport properties. Arising from partial substitutions of Bi3+ by Ca2+ and Li+, the carrier concentration significantly increased because of massively introduced hole carriers. More importantly, we reveal that the carrier mobility can be enhanced by light element Li doping arising from largely reduced carrier scattering. The largest carrier mobility value reaches 8.06 cm2V−1s−1, which is significantly enhanced as compared with previously reported doped BiCuSeO. As a result, the electrical conductivity increases to 288 Scm−1 and the power factor reaches as high as 804 μW m−1K−2 at room temperature in Bi0.84Li0.08Ca0.08CuSeO, which is about 288 and 53 folds as compared with pristine BiCuSeO, respectively. Furthermore, Li and Ca codoping not only leads to dual-atomic point-defects scattering, but also can effectively scatter high-frequency phonons through introducing calcium oxide nanoprecipitates, resulting in a low lattice thermal conductivity (0.54 Wm−1K−1 at 873 K). The combination of optimized power factor and thermal conductivity contributes to a high thermoelectric figure of merit ZT (∼0.9 at 873 K) in Bi0.88Li0.06Ca0.06CuSeO. This study provides a new pathway for enhancing thermoelectric performance of BiCuSeO via light element doping and introducing nanostructures.