Precise Microstructural and Stoichiometric Control Advances Flexible Ag₂Te Thin-Film Thermoelectrics for Wearable...

Ag₂Te has emerged as a promising n-type flexible thermoelectric material for harvesting body heat in wearable electronics. However, previously reported thin films have suffered from low carrier mobility and limited power factor of < 10 µW cm^-1 K^-2. Here, we present a two-step evaporation strategy on polyimide substrates at 280°C, followed by post-annealing at 250°C, enabling precise microstructural and stoichiometric control. This approach yields Ag₂Te films with an exceptional room-temperature carrier mobility of 4756 cm² V^-1 s^-1 and a power factor of 17.9 µW cm^-1 K^-2, outperforming both prior thin-film and bulk counterparts. The resulting devices exhibit excellent flexibility and rapid transient voltage response across temperature differences of 10-40 K, delivering power density up to 11 W m^-2. Integrated into robotic systems and light emitting diode arrays, these films enable thermally triggered actuation and sensing, underscoring their potential for efficient, adaptable, and self-powered applications in next-generation Internet of Things devices and sensor networks.