Tin selenide might considerably exceed the efficiency of current record holding thermoelectric materials made of bismuth telluride. However, it was thought its efficiency became enormous only at temperatures above 500 degrees Celsius. Now measurements at the BESSY II and PETRA IV synchrotron sources show that tin selenide can also be utilised as a thermoelectric material at room temperature – so long as high pressure is applied.
The thermoelectric effect has been known since 1821: with certain combinations of materials, a temperature difference generates an electric current. If one end of the sample is heated, for example using waste heat from a combustion engine, then part of this otherwise lost energy can be converted into electrical energy. However, the thermoelectric effect in most materials is extremely small. This is because to achieve a large thermoelectric effect, heat conduction must be poor, whereas electrical conductivity must be high. However, heat conduction and electrical conductivity are almost always closely associated.
For this reason, the search for thermoelectric materials concentrates on compounds with special crystalline structures such as bismuth telluride (Bi2Te3). Bismuth telluride is one of the best thermoelectric materials known to date. However, both bismuth and tellurium are rare elements, which limit their large-scale use. So the search continues for suitable thermoelectric materials among more abundant non-toxic elements.