  Identification of novel materials with enhanced thermoelectric (TE)
performance is critical for advancing TE research. In this direction, this is
the first report on TE properties of low-cost, nontoxic, and abundant
core-shell Cu@Cu2O nanocomposites (NCs) synthesized using a facile and cheap
solution-phase method. They show ultralow thermal conductivity of nearly 10-3
of copper bulk value, large thermopower ~0.373 mVK-1, and consequently, a TE
figure of merit (ZT) of 0.16 at 320 K which is larger than those of many of the
potential TE materials such as PbTe, SnSe and SiGe, showing its potential for
TE applications. The ultralow thermal conductivity is mainly attributed to the
multiscale phonon scattering from intrinsic defects in Cu2O, grain boundaries
(GBs), lattice-mismatched interface as well as dissimilar vibrational
properties. The large thermopower is associated with sharp modulation in
carrier density of states (DOS) due to charge transfer between Cu and Cu2O
nanoparticles (NPs), and carrier energy filtering.
