High Thermoelectric Performance in Non‐Toxic Earth‐Abundant Copper Sulfide

A new type of high performance thermoelectric material Cu2-xS composed of non-toxic and earth-abundant elements Cu and S is reported. Cu2-xS surprisingly has lower thermal conductivity and more strikingly reduced specific heat compared to the heavier Cu2Se, leading to an increased zT to 1.7. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.