Low‐Cost, Energy‐Saving, Room‐Temperature Synthesis of Ductile Thermoelectric Semiconductors

Flexible thermoelectric has recently attracted great attention in wearable technologies. Ag 2 (Se,S)‐based ductile materials are promising candidates for flexible thermoelectric applications. However, conventional melting methods with high‐temperature routes (>1000°C), which are commonly employed for the synthesis of these materials, are energy‐intensive and limited in achieving precise control over composition and homogeneity. In this work, a simple chemical reaction route was employed to synthesize Ag 2 (Se,S)‐based materials at room temperature, enabling highly homogeneous distribution and good chemical stoichiometric control. Among the S‐substituted compositions, Ag 2 Se 0.7 S 0.3 exhibited the best thermoelectric performance, and excess Ag was subsequently incorporated to regulate carrier transport. Although the Ag‐excess bulk sample achieved a zT value of 0.54 at 340 K due to reduced thermal conductivity, its power factor remained limited. Hot‐rolling deformation was therefore introduced to promote an anisotropic microstructure with grain alignment, which facilitates carrier transport and increases carrier mobility. The optimized Ag 2.05 Se 0.7 S 0.3 film achieved a maximum power factor of 13.88 µW cm −1 K −2 at 340 K. Furthermore, a six‐leg in‐plane thermoelectric device fabricated from this material delivered a normalized maximum power density of 0.44 W m − 1 under Δ T = 37.4 K, demonstrating the potential of this cost‐effective and energy‐saving room‐temperature synthesis strategy for flexible thermoelectric applications.