Thermoelectric energy conversion is based on the Seebeck
effect and allows for the generation of electricity
directly from a supply of thermal energy. The conversion
efficiency is governed by the thermoelectric figure of merit
(ZT), ZT = S2
rT/j, where S is the Seebeck coefficient, r is
the electrical conductivity, j is the thermal conductivity,
and T is the absolute temperature at operation [1,2]. The
ZT value directly affects the efficiency of thermoelectric
conversion, i.e., larger ZT means higher efficiency. Recent
advances in material science provide a path to achieve high
ZT values by coordinating the conflicts among S, r and j.
Tailoring the material structures is considered an effective
approach to facilitate independent control of Seebeck coef-
ficient and electrical conductivity [3–6].
Within the last years, a progressive improvement in the
ZT value at room temperature has been demonstrated