High-performance jointless all-organic Ohmic junction thermoelectric generators

Organic thermoelectric materials offer unique advantages for wearable electronics (WEDs) due to their flexibility and scalable production. Recent advancements in high-performance n-type materials highlight the potential for developing all-organic thermoelectric devices. This work developed continuous and flexible all-organic thermoelectric films based on p-type and n-type polymers, and carboxymethyl cellulose (CMC). By employing direct drop-coating of PEDOT:PSS-CMC (PHCM) and PBFDO-CMC (PBCM) suspensions, a stable two-dimensional vertical heterojunction was fabricated. The fabricated PHCM and PBCM films demonstrated high electrical conductivity, excellent flexibility, and exceptional mechanical stability. Interestingly, these films exhibit good electrical contact with each other, enabling the construction of thermoelectric modules with n- and p-legs without the need for metal interconnects. Remarkably, the device retained 99 % of its electrical performance after 10,000 bending cycles and demonstrated stability under water immersion for 72 hours. The strong mechanical bonding between the n-leg and p-leg, ensured by the intertwining of cellulose chains, is crucial for wearable applications that are typically subjected to mechanical stress. Finally, the absence of metal interconnects offers a more sustainable pathway for recycling of all-organic wearable thermoelectric generators. This work pioneers a sustainable pathway for flexible electronics, thus advancing wearable energy harvesting and temperature-sensing applications.