In situ Synthesized Staggered-Layer-Boosted Flexible Ag2Se and Cu2Se Thin Films for Wearable Thermoelectric Power Generators

Abstract

Flexible thermoelectric generators (TEGs) have been considered as a promising power source for rapidly developing wearable microelectronic devices, but how to integrate high-performance materials and device design to prepare an available wearable TEGs is still challenging. In this study, n-type silver selenide (Ag2Se) and p-type copper selenide (Cu2Se) films are prepared by in situ full metal selenization strategy combined with screen-printing technique, avoiding a high-temperature process and expensive equipments. Further, a 3D structured thermoelectric module with 42 thermoelectric p-n leg pairs is designed and configured by vertically embedding Ag₂Se and Cu₂Se thin films into a 4 mm-thick silicone layer that provides insulation and structural support. The device consistently delivers power, achieving the maximum open-circuit voltage of 113 mV at a temperature difference of 60 K, with a maximum power density of 234.3 µW cm−2. Under bending stress, the flexible TEG still has 81% retention rate of initial power density after 1500 bending cycles, indicating the good bending property. It can also generate a voltage of 3.6 and 7 mV, respectively, when worn on an arm with or without a fan expanding temperature difference. The work highlights a simple method to obtain efficient selenide thermoelectric films for cost-effective flexible 3D structured TE devices.