New Design Improves Thermoelectric Semiconductor

Guest_Jim_* - May 3, 2012 11:18AM in Science & Technology

Many processes are imperfect and waste energy by generating unwanted heat. Car engines and electronics are two examples. As just improving efficiency is not always easy, researchers are working on thermoelectric materials that convert heat differences into electricity. Researchers at Boston College and MIT have recently found a way to significantly improve the efficiency of one of these materials.

Silicon germanium, SiGe, is a semiconducting alloy that has been used for its thermoelectric properties for years. Some NASA missions actually use it in their radioisotope thermoelectric generators. The researchers applied a technique used in the thin-film semiconductor industry called 3D modulation-doping strategy which increased electrical conductivity while decreasing thermal conductivity.

Ideally a thermoelectric material will conduct electricity well, but not heat. The reason heat cannot be allowed to flow well is because a temperature difference is needed to generate an electric current. If the heat is able to quickly diffuse through the material, there will no longer be a temperature difference.

While the increase in performance is important, the process also reduced the amount of germanium used in the alloy by 30%. Germanium is not cheap, so this kind of reduction helps make the thermoelectric material more economically viable.