Light Element Doping and Introducing Spin Entropy: An Effective Strategy for Enhancement of Thermoelectric Properties in BiCuSeO.

The Seebeck coefficient and carrier mobility in reported doped BiCuSeO system are too small, which limits the improvement of thermoelectric performance. Here, we proposed a novel strategy for optimizing thermoelectric performance by increasing Seebeck coefficient and boosting carrier mobility. We demonstrate that light element Li doping boosts carrier mobility (7.39 cm2 V-1 s-1) due to largely reduced carrier scattering, which results in about 2-fold increase in carrier mobility as compared with reported Bi0.875Ba0.125CuSeO through modulation doping or microstructure texturing. Moreover, the Seebeck coefficient remarkably increases by contribution of spin entropy induced by magnetic ions Mn incorporation. The enhancement of Seebeck coefficient coupled with enhanced electrical conductivity result in high power factor. Furthermore, nanoprecipitates and dual-atom point defect leads to a significant reduction of lattice thermal conductivity. Therefore, a high ZT value of 0.9 was achieved at 873 K through optimizing power factor while maintaining low thermal conductivity. Our findings provide a new perspective for designing prospective thermoelectric materials.