A Facile Etching-Exfoliation Method for High-Performance Flexible Ag₂Se Based Thermoelectric Films

Ag₂Se-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, Ag₂Se flexible films have achieved thermoelectric performance comparable to high-cost Bi₂Te₃ 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 Ag₂Se 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 Ag₂Se 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.