A Facile Etching‐Exfoliation Method for High‐Performance Flexible Ag ₂ Se Based Thermoelectric Films

ABSTRACT Ag ₂ Se‐based films are promising candidates for flexible thermoelectric devices (F‐TEDs) owing to their excellent electrical transport properties near room temperature. Through compositional engineering and orientation control, Ag ₂ Se flexible films have achieved thermoelectric performance comparable to high‐cost Bi ₂ Te ₃ materials. However, current fabrication methods often rely on complex processes and expensive equipments, hindering large‐scale commercialization. Here, we report a facile, low‐cost, and environmentally robust approach to fabricate highly oriented Ag ₂ Se films. Through rational post‐treatments, the crystalline structure and chemical composition are finely tuned to achieve an optimal balance between carrier concentration and mobility. As a result, the Ag ₂ Se films exhibit a competitive average power factor of ∼27 µW cm ⁻¹ K ⁻² (298–393 K) together with excellent mechanical flexibility. Furthermore, an in‐plane device delivers an outstanding normalized power density of 3.4 µW cm ⁻² K ⁻² at a temperature difference of 10 K, outperforming most reported F‐TEDs. Importantly, this simple yet effective fabrication strategy offers a scalable pathway toward the commercialization of high‐performance and flexible thermoelectric technologies.