Development of flexible thermoelectric devices offers exciting opportunities for wearable applications in consumer electronics, healthcare, human–machine interface, etc. Despite the increased interests and efforts in nanotechnology‐enabled flexible thermoelectrics, translating the superior properties of thermoelectric materials from nanoscale to macroscale and reducing the manufacturing costs at the device level remain a major challenge. Here, an economic and scalable inkjet printing method is reported to fabricate high‐performance flexible thermoelectric devices. A general templated‐directed chemical transformation process is employed to synthesize several types of 1D metal chalcogenide nanowires (e.g., Ag2Te, Cu7Te4, and Bi2Te2.7Se0.3). These nanowires are made into inks suitable for inkjet printing by dispersing them in ethanol without any additives. As a showcase for thermoelectric applications, fully inkjet‐printed Ag2Te‐based flexible films and devices are prepared. The printed films exhibit a power factor of 493.8 µW m−1 K−2 at 400 K and the printed devices demonstrate a maximum power density of 0.9 µW cm−2 K−2, both of which are significantly higher than those reported in state‐of‐the‐art inkjet‐printed thermoelectrics. The protocols of metal chalcogenide ink formulations, as well as printing are general and extendable to a wider range of material systems, suggesting the great potential of this printing platform for scalable manufacturing of next‐generation, high‐performance flexible thermoelectric devices.

Thermoelectric modules can convert waste heat directly into useful electricity, providing a clean and sustainable way to use fossil energy more efficiently. Mg3Sb2-based alloys have recently attracted considerable interest from the thermoelectric community due to their nontoxic nature, abundance of constituent elements, and excellent mechanical and thermoelectric properties. However, robust modules based on Mg3Sb2 have progressed less rapidly. Here, we develop multiple-pair thermoelectric modules consisting of both n-type and p-type Mg3Sb2-based alloys. Thermoelectric legs based on the same parent fit in each other in terms of thermomechanical properties, facilitating module fabrication and ensuring low thermal stress. By adopting a suitable diffusion barrier layer and developing a new joining technique, an integrated all Mg3Sb2-based module demonstrates a high efficiency of 7.5% at a temperature difference of 380 K, exceeding the state-of-the-art same-parent thermoelectric modules. Moreover, the efficiency remains stable during 150 thermal cycling shocks (∼225 h), demonstrating excellent module reliability.