Three-Stage Thin-Film Superlattice Thermoelectric Multistage Microcoolers with a ΔT max of 102 K

Abstract

Te 3 -based superlattice (SL) thermoelectric (TE) devices are an enabling technology for high-power and low-temperature applications, which include low-noise amplifier cooling, electronics hot-spot cooling, radio frequency (RF) amplifier thermal management, and direct sensor cooling. Bulk TE devices, which can pump heat loads on the order of 10 W/cm 2 , are not suitable in these applications due to their large size and low heat pumping capacity. Recently, we have demonstrated an external maximum temperature difference, DT max , as high as 58 K in an SL thin-film p-n couple. This state-of-the-art couple exhibited a cold-side minimum temperature, T cmin , of À30.9°C. We regularly attain DT max values in excess of 53 K, in spite of the many significant electrical and thermal parasitics that are unique to thin-film devices. These measurements do not use any complex thermal management at the heat sink to remove the heat flux from the TE deviceÕs hot side. We describe here multistage SL cooling technologies currently being developed at RTI that can provide useful microcooling cold-side temperatures of 200 K. This effort includes a three-stage module employing independently powered stages which produced a DT max of 101.6 K with a T cmin of À75°C, as well as a novel two-wire three-stage SL cascade which demonstrated a T cmin of À46°C and a DT max of nearly 74 K. These RTI modules are only 2.5 mm thick, significantly thinner than a similar commercial three-stage module (5.3 mm thick) that produces a DT max of 96 K. In addition, TE coolers fabricated from these thin-film SL materials perform significantly better than the extrapolated performance of similar thickness bulk alloy materials.

Generation of Nanosized Particles during Mechanical Alloying and Their Evolution through the Hot Extrusion Process in Bismuth-Telluride-Based Alloys

“…As a result, only miniature modules with cooling surfaces of a few millimetres have been manufactured using thin-film thermoelectrics. 4,5 In contrast, bulk nanosized materials would present no practical difficulties for manufacturing processes for larger modules, but so far there is very limited information 6 indicating successful development of reliable technology based on such materials. On the other hand, there are several well-established micropowder metallurgy technologies resulting in decent thermoelectric material performance.…”

Superlattice-based thin-film thermoelectric modules with high cooling fluxes

“…Electrical constant resistance has a marked impact on the performance of thin thermoelectric modules since the magnitude of the contact resistance can be comparable to that of thermoelectric element itself. Bulk thermoelectric materials cannot be thinned below a few hundred microns, resulting in the modest maximum cooling flux of approximately 10 W cm −2 (refs 27 , 28 ). Epitaxial semiconductor films can be grown much thinner, resulting in a higher maximum cooling flux for thin-film modules.…”

Time-Dependent Finite-Volume Model of Thermoelectric Devices

“…This approach requires rewriting the ODEs (10)- (12), (26) in terms of bulk quantities such as resistances and capacitances. For example, (11), (12) become…”

“…Recent experimental and application interest in thermoelectric materials has been in thin films [5], [6] and the design of microscale energy converters [7]- [10]. Modern thermoelectric devices for specialist applications are often cascaded or multi-stage [11], [12] to optimize efficiency, Manuscript meaning that the Seebeck coefficient must be modeled as having a temperature dependence. This highlights the need for accurate models to guide design and experiment.…”