Optimized thermoelectric performance of flexible Bi_0.5Sb_1.5Te₃ thin film through PbTe incorporation

Being the most widely applied thermoelectric materials near room temperature, (Bi,Sb)₂Te₃ alloys have to face the performance deterioration above 400 K due to their intrinsic narrow bandgap. Increasing the dominant hole concentration and expanding the bandgap have been proven as effective strategies to suppress bipolar excitation through elemental substitution and nanoscale compositing. Herein, PbTe-incorporated Bi_0.5Sb_1.5Te₃ thin films were deposited on flexible polyimide substrates through intermittent magnetron cosputtering. The introduction of tiny amount of PbTe was found to have significant influences on the microstructure and orientation, atomic compositions, and carrier concentration. Profiting from the enhanced carrier concentration and altered effective mass, the descending in Seebeck coefficient above 400 K can be effectively inhibited, accompanied with the distinctly improved electrical conductively. Finally, the highest power factor of 16.38 μW cm⁻¹ K⁻² at 420 K and the highest average power factor of 14.62 μW cm⁻¹ K⁻² in the temperature range of 300–540 K were obtained in the Bi_0.5Sb_1.5Te₃/PbTe composite film containing 0.25% Pb, with the increments of 28.2% and 38.2% from those of the PbTe-free Bi_0.5Sb_1.5Te₃ film, respectively. These values are competitive among the flexible Bi_0.5Sb_1.5Te₃ thin films fabricated from the scalable routes.