Large Voltage Generation of Flexible Thermoelectric Nanocrystal Thin Films by Finger Contact

This paper demonstrates that thermal energy radiated from a human finger can be converted efficiently into electricity by a nanocrystal (NC) thin film that substantially suppresses thermal conduction, but still allows electric conduction. The converting efficiencies of the chalcogenide NC thin films with dimensions 40 μm × 20 μm × 20 nm, prepared on flexible substrates by a solution process, are maximized by adjusting the NC size. A Seebeck coefficient of S = 1829 μV K^-1, and a dimensionless thermoelectric figure-of-merit, ZT = 0.68 are achieved at ambient temperature for p- and n-type NC thin films, respectively. A thermoelectric array consisting of p- and n-type NC thin films generates a voltage of 645 mV for a temperature gradient of 10 K. Furthermore, the donut-shaped pn array can generate a voltage of 170 mV from the heat supplied by an individual's finger.