Realizing synergistic optimization of thermoelectric properties in n-type BiSbSe₃ polycrystals via co-doping zirconium and halogen

BiSbSe₃ is a promising thermoelectric material due to its ultralow thermal conductivity. Here, we demonstrate that it is possible to enhance the thermoelectric performance of n-type BiSbSe₃ by co-doping of zirconium and halogen (chlorine or bromine). Doping Zr induces the band convergence and resonant level, acting to enhance the effective mass. Halogen doping at Se site can further optimize the carrier density while maintaining high carrier mobility by reducing deformation potential. Thus, the synergistic optimization of effective mass, carrier density, and carrier mobility is realized in Zr and halogen co-doped BiSbSe₃. After Zr and halogen co-doping, the lattice thermal conductivity is effectively reduced by the increased scattering centers. Consequently, a maximum ZT of ∼0.83 at 800 K and an average ZT of ∼0.48 at 300–800 K are obtained in 3%Zr and 1%Br co-doped BiSbSe₃. Our investigation illustrates a feasible strategy to synergistically optimize the thermoelectric properties in n-type BiSbSe₃ polycrystals via co-doping effective elements.