  We have theoretically studied the thermoelectric properties of serially
coupled quantum dots (SCQD) embedded in an insulator matrix connected to
metallic electrodes. In the framework of Keldysh Green's function technique,
the Landauer formula of transmission factor is obtained by using the equation
of motion method. Based on such analytical expressions of charge and heat
currents, we calculate the electrical conductance, Seebeck coefficient,
electron thermal conductance and figure of merit (ZT) of SCQD in the linear
response regime. The effects of electron Coulomb interactions on the reduction
and enhancement of ZT are analyzed. We demonstrate that ZT is not a monotonic
increasing function of interdot electron hopping strength ($t_c$). We also show
that in the absence of phonon thermal conductance, SCQD can reach the Carnot
efficiency as $t_c$ approaches zero.
