Flexible Ag<sub>2</sub>Se-based thin-film thermoelectrics for sustainable energy harvesting and cooling.

Chen, Wenyi; Li, Meng; Wang, Xiaodong; Otte, Joseph; Zhang, Min; Zhang, Chengyang; Cao, Tianyi; Hu, Boxuan et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

The high cost and complexity of fabrication limit the large-scale application of flexible inorganic thermoelectric materials. Currently, Bi<sub>2</sub>Te<sub>3</sub>-based materials are the only commercially viable option, but the inclusion of Te significantly increases production costs. This study presents a simple and cost-effective method for fabricating flexible Ag<sub>2</sub>Se films, employing a combination of solvothermal synthesis, screen printing, and spark plasma sintering. The incorporation of a small amount of Te improves film density and facilitates Te diffusion doping, leading to Ag<sub>2</sub>Se films with a high power factor of 25.7 μW cm<sup>-1</sup> K<sup>-2</sup> and a figure of merit (ZT) of 1.06 at 303 K. These films exhibit excellent flexibility, retaining 96% of their performance after 1000 bending cycles at a 5 mm bending radius. Additionally, we design a flexible thermoelectric device featuring a triangular p-n junction structure based on these films. This device achieves a normalized power density of 4.8 μW cm<sup>-2</sup> K<sup>-2</sup> at a temperature difference of 20 K and a maximum cooling of 29.8 K with an input current of 92.4 mA. These findings highlight the potential of this fabrication method for developing thermoelectric materials and devices for energy harvesting and cooling applications.