  We theoretically investigate the enhancement of thermoelectric cooling
performance in thermoelectric devices made of materials with inhomogeneous
thermal conductivity, beyond the usual practice of enhancing thermoelectric
figure of merit ZT. The dissipation of Joule heat in such thermoelectric
devices is asymmetric which can give rise to better thermoelectric cooling
performance. Although the thermoelectric figure of merit and the
coefficient-of-performance are only slightly enhanced, both the maximum cooling
power and the maximum cooling temperature difference can be enhanced
significantly. This finding can be used to increase the heat absorption at the
cold end. The asymmetric dissipation of Joule heat also leads to thermal
rectification.
