Engineering high-performance BiSeTe ultra-thin film on flexible FEP

Flexible thermoelectric (TE) devices hold great promise for powering wearable electronics by harvesting the temperature difference between human skin and the environment. Conventional Bi2Te3, although efficient, suffers from rigidity and limited suitability for flexible applications, while organic alternatives typically lack sufficient TE performance. Here, we demonstrate an n-type BiSeTe thin film deposited on a flexible fluorinated ethylene propylene (FEP) substrate, incorporating a Cr buffer layer, achieving a room-temperature power factor of ∼3.9 μW.cm−1.K−2, which is within the range reported for flexible thin-film TE devices on polymer substrates. The film exhibits excellent mechanical resilience, retaining 90 % of its initial conductivity after 5000 bending cycles, and shows high thermal stability over 50 heating–cooling cycles with deviations below 1.5 %. A four-leg n-type prototype generates 10 mV and 70 nW at ΔT = 40 K, demonstrating its potential for powering low-energy wearable sensors. This work presents a scalable inorganic thin-film TE platform that effectively balances mechanical flexibility, device stability, and practical energy conversion performance for wearable and localized power generation applications.