Modulation doping promoted ultrahigh electron mobility and enhanced thermoelectric performance in PbTe

Modulation doping was proven to be a quite effective strategy to realize high electrical conductivity at a relative low charge carrier concentration in bulk thermoelectric materials. In this work, we used lightly doped PbTe-0.1 %Cu with minimal ionized impurity scattering as matrix material and PbS-0.8 %Cu with adequate electron concentration as electron reservoir to construct a modulation doping scenario. Such modulation doped PbTe/PbS heterostructures were characterized with high-angle angular dark field scanning transmission electron microscopy (HAADF-STEM). We achieved significantly improved carrier mobility in modulation doped (PbTe)1-x(PbS)x than homogeneously doped PbTe materials reported in literatures; meanwhile, we also obtained obviously reduced lattice thermal conductivity owing to the strong phonon scattering by the dislocation arrays at PbTe/PbS phase boundaries. An ultrahigh room temperature (323 K) figure of merit ZTRT ∼0.63 as well as remarkable average ZTavg ∼1.17 at 323–773 K were simultaneously realized in the sample (0.1 %Cu-PbTe)0.9(0.8 %Cu-PbS)0.1, both of which are among the highest ones for all reported PbTe-based thermoelectric materials so far.