Individualization of optimal operation currents for promoting multi-stage thermoelectric cooling

Cascading multiple thermoelectric coolers offers a promising approach to promote the cooling capability for a broad scale of applications at low temperatures. The variation in thermoelectric properties versus temperature and the size of each constituent cooler, lead to a challenge in a full realization of cooling capability by an identical operating current for all stages. In this work, it is revealed in a commercial 3-stage thermoelectric cooler that, a further 10% temperature reduction can be realized by individualizing the optimal operating currents for each stage. Even at the lowest achievable temperature (∼191 K) operating under an identical operating current, this work enables a cooling power density as high as 4 kW/m2. This further results in a fast cooling to 191 K in only about 1 min, corresponding to a nearly doubled cooling rate to this temperature. The optimal operating currents for each stage are revealed to be very close to those operated as single-stage devices, thus, enabling a convenient guidance and strategy for promoting the cooling capability of multiple-stage thermoelectric coolers targeting at lower-temperature applications.