Screen printed thermoelectrics: balancing performance, flexibility, and wearable energy harvesting

The increasing consumption of fossil fuels and the harm that industrial waste heat pose to the environment have challenged researchers to develop sustainable and self-powered energy systems. Flexible thermoelectric generators, which use the Seebeck effect to turn heat into electricity, have become attractive power sources for wearable electronics and personalized health monitoring systems. This review aims to provide a comprehensive overview of screen-printed thermoelectric materials and devices, spanning inorganic, organic, and hybrid material systems. The article opens with an overview of thermoelectric principles, device configurations, and thermoelectric materials. It then examines chalcogenide-based inorganic materials, in particular, tellurides and selenides, followed by organic and hybrid thermoelectric materials such as PEDOT:PSS, carbon nanotubes, and organic–inorganic composites. Inorganic chalcogenide-based materials, such as tellurides and selenides, display high power factors and enhanced figures of merit, however, suffers from brittleness and poor mechanical flexibility. Despite their limited thermoelectric efficacy, organic thermoelectric materials are lightweight, flexible, and cost-effective. To improve power output, longevity, and stability under repetitive bending, hybrid thermoelectric materials combine the mechanical compliance of organic matrices along with the high electrical performance of inorganic components. For large-area device production, screen-printing methods have garnered special attention because of their scalability and applicability, combined with flexible substrate compatibility. The review reports recent developments in material design tactics, ink composition, printing parameters, post-processing techniques, as well as configurations of wearable and textile-based thermoelectric generators and device performance. Finally, the existing challenges and prospective research directions toward developing adaptable, sustainable, and highly efficient thermoelectric energy-harvesting devices are discussed.