A Label‐Like Monolithic Organic Thermoelectric Generator Enabled by Local Inkjet Doping of Aligned Polymer Films

Abstract The proliferation of distributed microelectronics and sensors necessitates adaptable, scalable, and cost‐effective power supplies. Organic thermoelectric generators (TEGs) that promise to harness heat sustainably and cost‐effectively are seen as pivotal elements in shaping future sensor infrastructures. Recent strides in morphological control through the alignment of conjugated polymer backbones have enhanced the thermoelectric performance of doped organic semiconductors to record values, matching expectations for real applications. However, the hurdles in crafting and deploying organic TEGs effectively exploiting aligned polymer films remain unexplored. This work presents a design and fabrication method to incorporate aligned films into a thin label‐like TEG. Thin films of regioregular poly(3‐hexylthiophene) (P3HT) and poly(2,5‐bis((7‐butoxyheptyl)thiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT‐⁸O) are aligned via high‐temperature rubbing technique inducing a high degree of anisotropy in their charge transport properties. The crystal structure and anisotropy of the films are exploited to realize monolithic TEGs by patterning conductive thermoelements via local inkjet doping of films transferred on ultrathin parylene substrates. The TEGs based on aligned P3HT and PBTTT‐⁸O exhibit exceptional TEG power factors of 0.33 and 1.04 nW cm⁻² K⁻², respectively. Lastly, as a proof‐of‐concept use case for the TEGs, a thermoelectrically‐powered volume‐indicating label is presented as a potential application in the healthcare and food industries.