  Using first-principles calculations combined with Boltzmann transport theory,
we investigate the effects of topological edge states on the thermoelectric
properties of Bi nanoribbons. It is found that there is a competition between
the edge and bulk contributions to the Seebeck coefficients. However, the
electronic transport of the system is dominated by the edge states because of
its much larger electrical conductivity. As a consequence, a room temperature
value exceeding 3.0 could be achieved for both p- and n-type systems when the
relaxation time ratio between the edge and the bulk states is tuned to be 1000.
Our theoretical study suggests that the utilization of topological edge states
might be a promising approach to cross the threshold of the industrial
application of thermoelectricity.
