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 Ag$_2$(Se$_{1-x}$S$_x$)$_{1.05}$-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 Ag$_2$Se 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 weightnormalized 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.