A pair
of n-type Bi2Te3–x
Se
x
and p-type (Bi,Sb)2Te3 is known as a promising candidate for assembling a
high thermoelectric efficiency module operating at near room temperature.
While the dimensionless figure of merit (zT) of p-type
(Bi,Sb)2Te3 is commonly larger than 1.0, n-type
Bi2Te3–x
Se
x
has a lower zT value of ∼0.8
at room temperature. Here, we aim to enhance the zT of n-type Bi2Te3–x
Se
x
through the energy filtering effect
that can improve the Seebeck coefficient by adding Au. In the Bi2Te2.8Se0.2 + 5 at % Au composite, the
Seebeck coefficient is significantly improved, and the electrical
resistivity does not change significantly, leading to an approximately
twice as high power factor as that of the non-Au-added one at near
room temperature. Also, the addition of Au suppresses the thermal
conductivity. These advantages result in a maximum zT of over 1.0 at room temperature and average zT value
of 1.05 at T = 300–400 K, an ∼75% improvement,
which is comparable to those of the reported n-type Bi2Te3-based materials. Also, Au addition shows no negative
effect on the mechanical properties as well as high-temperature stability
of Bi2Te3–x
Se
x
. These results indicate that Au addition is a promising
method to improve the thermoelectric properties of n-type Bi2Te3–x
Se
x
used for assembling a practical thermoelectric module operating
at near room temperature.