Stretchable wearable thermoelectric generator from <i>in situ</i> reaction wavy tellurium films

Recent years have witnessed substantial advancements in wearable thermoelectric generators (TEGs) leveraging 2D thin-film structures. However, the rational design of TEGs that harmonizes high output performance, stretchability, and comfort remains a challenge. Herein, p-type and n-type thermoelectric units are alternately arranged on a flexible tellurium (Te) film using a solvothermal method combined with an in situ reaction. This methodology facilitates the fabrication of a wearable wavy structure TEG with an impressive stretchability of up to 300%. The effect of the geometric parameters of the wavy structure on TEG performance is explored. The designed TEG with three p–n pairs (TEG-3pn) achieves an open-circuit voltage output of 50.46 mV at a temperature difference of 60 K. Demonstrations of thermal energy harvesting from the human wrist and a hot water cup underscored the TEG's efficient exploitation of vertical temperature gradients and its versatility for diverse applications. This work provides a straightforward and practical strategy for designing thin-film-based 3D TEGs, addressing both structural considerations and the impact of geometric parameters on performance.