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)/Ag2Se composite film on nylon membrane prepared by first in-situ synthesis of PVP coated Ag2Se 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 Ag2Se 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.