Printed origami thermoelectric generator achieves > 20 Wm^-² from low-grade heat via material and process design

Printing facilitates low-cost thermoelectric generators to power battery-free internet-of-things devices, wearables, and Industry 4.0 systems. However, scaling up requires printable thermoelectric materials with good mechanical properties and high performance. Here, we report a high-performance Ag₂(Se_1-xS_x)_1.05-based n-type printed thermoelectric film through a combination of engineering non-stoichiometric defects and sulfur substitution. An optimal sulfur substitution of 2 at. % facilitates an excellent flexibility and a power factor of~16 µWcm^-1 K^-2 at 360 K, a 65 % increase compared to a pristine Ag₂Se film. A fully printed origami-thermoelectric generator produces a maximum power output $P_{\max }$ of 907 µW at a temperature difference of 80 K. A record-high power density p_d of 21 W m^-2 (corresponding to 800 µW g^-1 as a weight-normalized power density) is achieved, twice that of previously reported origami-thermoelectric generators. These results highlight cost-effective manufacturing of thermoelectric generators with the capability to power next-generation autonomous electronic devices.