Ultra-flexible β-Cu2-δSe-based p-type printed thermoelectric films

Flexibility in a printed thermoelectric (TE) material is vital for low-cost manufacturing of shape-conformable TE devices. In this work, a one-pot facile method was adapted to prepare a Cu-Se-based printable ink. The ink was printed on flexible substrates followed by sintering to let β-Cu2-δSe phase be formed. The film is found to be exceptionally flexible with a change in film resistance < 30 % after 100 bending cycles. The performance of the flexible film then was enhanced by substituting ´Se` with ´S`. At room temperature (RT), a power factor of 250 µWm−1K−2 with a thermal conductivity κ of 0.52 Wm−1K−1 is attained in the 10 at.% S substituted film. Figure-of-merit ZT values of 0.15 at RT and 0.21 at 375 K are achieved. For ∆T of 45 K, a maximum power output of 0.32 μW with an open-circuit voltage VOC of 12 mV is demonstrated using a TE-generator (Flex-TEG) with two thermocouples made of the prepared material.