Description: Thermoelectric devices are critical to multiple NASA missions for power conversion with radioisotope sources. At present, commercially available TE devices typically offer limited heat-to-electricity conversion efficiencies, well below the fundamental thermodynamic limit, calling for the development of higher efficiency materials. The team of MicroXact Inc. and Virginia Tech is proposing to develop a revolutionary high efficiency thermoelectric material fabricated on completely new fabrication principles. The proposed material and device will provide NASA with much needed highly efficient (ZT>1.6), macroscopically thick (from 100s of micrometers to over a millimeter) thermoelectric material that will permit >15% conversion efficiency of thermoelectric generation when using high grade space-qualified sources. The proposed material is comprised of PbTe/PbSe three-dimensional "wells" of PbTe/PbSe quantum dot superlattices (QDS) fabricated by a conformal coating of a structured silicon substrate with electrochemical Atomic Layer Deposition (eALD). In Phase I of the project the feasibility of the approach will be demonstrated by proving ZT>1.6. In Phase II the team will fabricate the thermoelectric generator, and will demonstrate conversion efficiencies exceeding 15%. After Phase II, MicroXact will commercialize the technology.

Benefits: The largest immediate NASA application of the proposed thermoelectric materials is the radioisotope thermoelectric generator, already being used in a large number of NASA missions. The unmatched efficiency combined with the light weight of the proposed material will provide the competitive advantage to MicroXact sufficient for successful market penetration, and will result in significant savings to NASA. Other potential NASA applications include energy recovery from processors and other electronics. The proposed concept, when developed and commercialized, is expected to cause a significant impact on the cost, safety and reliability of future NASA missions.

The proposed ultraefficient thermoelectric materials and devices are expected to find applications in automotive and aviation industry (to reduce the fuel consumption), as well as in electronic device cooling (microprocessors, focal plane arrays, etc.), food storage/processing (wine cellars, refrigerant-free refrigerators). Automotive applications are expected to be the most important market for the proposed technology due to both the large size and readiness of the market.