Roll‐to‐Roll Manufacturing of Flexible Thermoelectric Semiconductors Using Low‐Level Direct‐Current Sputtering

Direct‐current (DC) sputtering combined with roll‐to‐roll processing offers a highly competitive approach for scaling up the manufacturing of flexible functional thin films. However, its application to less‐conductive functional materials, such as semiconductors, remains limited due to charge buildup and arcing on the target. This study investigates the intrinsic relationships between DC sputtering power and the surface topography, elemental composition, crystallography, and thermoelectric properties of flexible thin‐film semiconductors. We explore low‐level DC power for room‐temperature roll‐to‐roll sputtering of Bi‐Te thermoelectric films, identifying an optimal power window that avoids charge‐buildup effects on the semiconductor target. Low‐power DC sputtering enables controlled crystallographic, microstructural, and compositional characteristics, thereby modulating electrical transport properties and, consequently, thermoelectric performance. As a result, a room‐temperature figure of merit of ∼0.1 is achieved at an optimal power of 0.22 kW while maintaining high‐throughput roll‐to‐roll manufacturability. Device‐level validation is demonstrated using a flexible thermoelectric generator, showing output performance consistent with COMSOL simulations.