Beating the maximum cooling limit with graded thermoelectric materials

摘要

The maximum cooling temperature of a uniform thermoelectric material is limited by its nondimensional figure of merit ZT. Conventionally cascaded stages or materials with a larger figure of merit are needed to obtain a higher cooling temperature. In this letter, the authors prove that the maximum cooling in an optimally graded single-stage device could be much larger than the value predicted based on the highest local ZT of the material. The cooling enhancement is attributed to the redistribution of the Joule heating and Peltier cooling profiles along the current and heat flow directions.