Ultrahigh performance polyvinylpyrrolidone/Ag2Se composite thermoelectric film for flexible energy harvesting

Flexible thermoelectric generator (f-TEG) has been considered to be a competitive candidate for powering wearable electronics and node sensor of internet-of-things. Herein, we report a polyvinylpyrrolidone (PVP)/Ag 2 Se composite film on nylon membrane prepared by first in-situ synthesis of PVP coated Ag 2 Se nanostructures (NSs), then vacuum assisted filtration of the NSs and finally hot pressing. High-resolution scanning and transmission electron microscope observations reveal that the PVP is located at the wall of pores and most Ag 2 Se grains are with coherent interfaces. Because of the unique microstructure and synergistic effect of the two components, an optimal composite film exhibits an ultrahigh power factor of ~ 1910 μW m −1 K −2 (corresponding ZT ~ 1.1) at 300 K and outstanding flexibility (only a 5.5% decrease in power factor after 1000 times bending around a 4 mm radius rod). An assembled 6-leg f-TEG produces 4.16 μW and the maximum power density is 28.8 W m −2 at a temperature difference of 29.1 K. This work demonstrates that insulating polymer can act as a great additive for improving both the TE properties and flexibility of inorganic TE films via fine design. The as-prepared composite film shows great promise for directly converting low-grade heat into electrical energy near room temperature.