Enhancement of the thermoelectric figure of merit in a quantum dot due to the Coulomb blockade effect

We investigate the figure of merit of a quantum dot (QD) in the Coulomb blockade regime. It is found that the figure of merit ZT may be quite high if only single-energy level in the QD is considered. On the other hand, with two or multienergy levels in the QD and without the Coulomb interaction, the ZT is strongly suppressed by the bipolar effect due to small level spacing. However, in the presence of the Coulomb interaction, the effective level spacing is enlarged and the bipolar effect is weakened, resulting in ZT to be considerably high. Thus, it is more likely to find a high efficient thermoelectric QDs with large Coulomb interaction. By using the parameters for a typical QD, the ZT can reach over 5.