High-Performance Ag-Se-Based n-Type Printed Thermoelectric Materials for High Power Density Folded Generators.

High-performance Ag-Se-based n-type printed thermoelectric (TE) materials suitable for room-temperature applications have been developed through a new and facile synthesis approach. A high magnitude of the Seebeck coefficient up to 220 μV K and a TE power factor larger than 500 μW m K for an n-type printed film are achieved. A high figure-of-merit ∼0.6 for a printed material has been found in the film with a low in-plane thermal conductivity κ of ∼0.30 W m K. Using this material for n-type legs, a flexible folded TE generator (flexTEG) of 13 thermocouples has been fabricated. The open-circuit voltage of the flexTEG for temperature differences of Δ = 30 and 110 K is found to be 71.1 and 181.4 mV, respectively. Consequently, very high maximum output power densities of 6.6 and 321 μW cm are estimated for the temperature difference of Δ = 30 K and Δ = 110 K, respectively. The flexTEG has been demonstrated by wearing it on the lower wrist, which resulted in an output voltage of ∼72.2 mV for Δ ≈ 30 K. Our results pave the way for widespread use in wearable devices.