High-performance screen-printed Ag-doped Bi0.5Sb1.5Te3 films with superior flexibility via polymer interlayer strategy

A polymer interlayer strategy was developed for screen-printed Bi 2 Te 3 -based films. • The film retains 94.16% conductivity after 5000 bending cycles at 15 mm. • Ag doping yields a high power factor of 3040.59 μW·m –1 ·K –2 at 423 K. Screen-printed Bi 2 Te 3 -based films are promising for large-scale flexible thermoelectric applications in wearable devices, however, the bending stability of such films is severely limited by the poor adhesion between the film and the commonly used polyimide substrate. To address this issue, this work introduces a polymer interlayer with low-softening-point between the thermoelectric film and the substrate to form a robust, molecular-scale bonded interface during sintering, which effectively mitigates bending-induced delamination and cracking of the Bi 2 Te 3 -based film. Consequently, the Ag-doped Bi 0.5 Sb 1.5 Te 3 film exhibits excellent mechanical stability, retaining over 94.16 % of the initial conductivity after 5000 bending cycles at a bending radius of 15 mm. Furthermore, Ag doping optimizes electrical performance by simultaneously increasing carrier concentration through cationic substitution and promoting a highly ordered lamellar structure that suppresses grain boundary scattering. This dual effect yields a superior power factor of 3040.59 μW·m –1 ·K –2 at 423 K. A thermoelectric generator fabricated from five film legs achieves a maximum output power density of 24.30 μW·mm –2 at a temperature difference of 30 K, demonstrating the practical viability of this approach for wearable applications. Download: Download high-res image (349KB) Download: Download full-size image