Thermoelectric Ag‐Doped Bi ₂ Se ₃ Heterostructure Films for Synergistic Energy Harvesting and Storage in Flexible Electronics

Abstract In response to the high cost and toxicity of traditional Bi ₂ Te ₃ thermoelectric (TE) materials, this study employs a cation doping strategy to significantly optimize the TE performance of Bi ₂ Se ₃ films, achieving a power factor of 252.6 µW m ⁻¹ K ^{− 2} at 440 K, which is the highest value for Bi ₂ Se ₃ ‐based flexible TE films synthesized by wet chemical methods. This improvement is attributed to the increase in electrical conductivity induced by Ag doping and the synergistic effects of energy filtering and doping effects. In addition, the Ag‐doped Bi ₂ Se ₃ film exhibits excellent flexibility and stability with only a 7% decrease in electrical conductivity after undergoing 2000 bends (with a radius of 4 mm). A flexible TE generator constructed based on the film outputs a power density of 123.4 µW cm ^{− 2} at a temperature gradient of 33.5 K, validating its effectiveness in TE conversion. In addition to traditional applications such as wearable and portable energy harvesting and sensing, the film also holds great potential in emerging fields such as photoelectric conversion and electrochemical energy storage systems. The high TE performance, flexibility, cost‐effectiveness, and multifunctional application of the film make it a promising candidate for next‐generation energy conversion and storage technologies.