Copper Sulfides: Earth‐Abundant and Low‐Cost Thermoelectric Materials

The depletion of nonrenewable energy sources insisted the search for new types of energy solutions. Thermoelectric conversion is one possible energy solution which converts waste heat into useful electricity. In the past several years, thermoelectric research developed many novel materials. Among these, most of the practically useful materials with better performance are based on Bi, Pb, Te, and Sb, but are toxic and expensive. There is a need of earth‐abundant, low‐cost, and less‐toxic compounds with superior thermoelectric performance so as to realize the large‐scale commercial applications. Recent studies have identified eco‐friendly thermoelectric materials based on the alloys of copper and sulfur, suggesting an alternative to the well‐established expensive thermoelectric materials. These compounds exhibit interesting electronic properties with better thermoelectric efficiency ( zT ). The structural properties permit to decouple electrical and thermal conductivities, which is an essential requirement to get improved efficiency. Several approaches, such as phase tuning, doping, nanostructure/microstructure designing, compound formation, etc., are chosen to increase the performance. On the whole, the present review summarizes the strategies and techniques that have been adopted to improve the thermoelectric behavior of copper sulfides and its compounds.