Ag₂Se/conjugated polyelectrolyte heterojunction films for high-performance flexible thermoelectrics

Silver selenide (Ag₂Se) has emerged as a promising room temperature thermoelectric material due to its intrinsically high performance, tunable electronic structure, and environmental compatibility. To further enhance its thermoelectric performance, a heterojunction engineering strategy is implemented herein by introducing a conjugated polyelectrolyte (CPE) at the Ag₂Se surface. The resulting ion-electron coupling forms an electron-rich interfacial channel that serves as a highly conductive charge transport pathway. Consequently, the planar heterojunction (PHJ) composite film delivers an electrical conductivity (σ) of 2209.7 ± 226.9 S cm^-1 and an impressive power factor (PF) of 2629.3 ± 291.0 µW m^-1 K^-2 at 303 K, representing the highest reported values among Ag₂Se-based composite films. Moreover, flexible thermoelectric generators (TEGs) fabricated from the PHJ film exhibit excellent mechanical flexibility, with only minor resistance changes after repeated bending at 35% curvature. These findings highlight the strong potential of the Ag₂Se/CPE heterojunction film as a high-performance platform for flexible thermoelectric power generation in next-generation wearable electronics.