Remarkable Enhancement of Thermoelectric Performance of Semicrystalline Polymer Films upon Incorporating A Nucleating Agent Additive

Nucleating agents are widely recognized for their ability to refine the solid-state morphology and microstructure of semi-crystalline polymers, significantly influencing their physicochemical properties. This study presents a simple yet effective strategy to dramatically improve the thermoelectric properties of semi-crystalline polymer films. By blending less than 1 wt% of the nucleating agent N,N'-(1,4-phenyl)diisonicotinamide (PDA) into Poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT-C14), we induce a controlled modulation of crystallization behavior, resulting in optimized microstructures with reduced structural disorder and improved charge carrier mobility. Systematic analysis of varying PDA concentrations identifies an optimal loading of 0.9 wt%, which yields a remarkable 45% increase in crystallinity relative to pristine PBTTT films. Under optimized doping conditions, the doped PBTTT-C14 film with 0.9 wt% PDA exhibits an exceptional electrical conductivity of 1800 S cm ⁻ ¹ and an optimal power factor of 150 µW m ^− 1 K ^− 2 , representing 105% and 384% improvements, respectively, over the doped pristine PBTTT-C14 film. These enhancements are primarily due to the synergistic effects of polymer chain extension and reduction of grain boundary size, which together mitigate grain boundary resistance and improve charge transport efficiency. Furthermore, the study elucidates the role of ion exchange doping in maintaining a high density of charge carriers without compromising the crystalline structure introduced by PDA. This research not only deepens the understanding of polymer thermoelectrics but also sets the stage for the development of innovative materials that could transform energy conversion technologies and polymer-based electronic devices.