Transparent and flexible thermoelectric thin films based on copper sulfides

As a promising thermoelectric material, CuS has attracted significant attention due to its high conductivity, abundance of elements, and eco-friendliness. However, the study on CuS-based thermoelectric thin films is still lacking, impeding the advancement of CuS-based thermoelectric devices. Herein, high-quality CuS thin films have been fabricated through a facile vulcanization process. The effects of vulcanization temperature and film thickness on the thermoelectric properties of CuS thin films have been investigated. An optimal high power factor of 73.25 μW/m−1 K−2 is found at 400 K for a 20 nm-thick sample, and the optical transmittance is over 80% in the visible light spectrum. Meanwhile, excellent flexibility of the CuS thin films has been demonstrated. These results demonstrate the high promise of CuS thin films for transparent and flexible thermoelectric device applications.