High performance Ag2Se/Ag/PEDOT composite films for wearable thermoelectric power generators

Herein, we report a Ag2Se/Ag/PEDOT (poly (3,4-ethylenedioxythiophene) composite film with a high thermoelectric performance and superior flexibility. First, we used PEDOT: poly (styrenesulfonate) (PSS) coated Se nanowires (NWs) as templates to prepare PEDOT:PSS coated Ag2Se/Ag composite powders, then Ag2Se/Ag/PEDOT composite films supported on porous nylon membrane were fabricated by vacuum assisted filtration and then hot pressing. An optimum composite film exhibits a high power factor of ∼1442.5 μW m−1 K−2, ultrahigh electrical conductivity (σ) of ∼5957.3 S cm−1 and superior flexibility (only 5.5% decrease in σ after 1000 times bending around a 4 mm radius rod) at RT. A certain amount of Ag phase in the composite film leads to an ultrahigh σ, while the PEDOT located at the interface between Ag and Ag2Se grains and at the surface of the Ag2Se grains causes the composite film with a low thermal conductivity. The excellent flexibility is due to the synergistic effect of the nylon membrane and PEDOT. Moreover, a 4-leg flexible thermoelectric power generator (f-TEG) assembled with the composite film shows a low internal resistance of ∼8 Ω, which makes it very possible to be integrated with a DC/DC converter for continually outputting power. The f-TEG produces a voltage of 5.6 mV and a maximum power of 1.8 μW (power density of 7.47 W m−2) at a temperature gradient of 27 K. This work provides an effective avenue for preparing high-performance flexible thermoelectric film with ultrahigh electrical conductivity.