Intrinsically Stretchable Organic Thermoelectric Polymers Enabled by Incorporating Fused‐Ring Conjugated Breakers

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 20; no. 37; pp. e2401966 - n/a
• Main Authors: Tseng, Chi‐Chun, Wang, Kuang‐Chieh, Lin, Po‐Shen, Chang, Chi, Yeh, Li‐Lun, Tung, Shih‐Huang, Liu, Cheng‐Liang, Cheng, Yen‐Ju
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.09.2024
• Subjects: amorphous segment; Copolymers; doping; Ferric chloride; fused‐ring; organic thermoelectrics; Polymers; Power factor; Strain; Stretchability; Thermoelectric materials; Thermoelectricity; doping; fused‐ring; organic thermoelectrics; stretchability; amorphous segment
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202401966

While research on organic thermoelectric polymers is making significant progress in recent years, realization of a single polymer material possessing both thermoelectric properties and stretchability for the next generation of self‐powered wearable electronics is a challenging task and remains an area yet to be explored. A new molecular engineering concept of “conjugated breaker” is employed to impart stretchability to a highly crystalline diketopyrrolepyrrole (DPP)‐based polymer. A hexacyclic diindenothieno[2,3‐b]thiophene (DITT) unit, with two 4‐octyloxyphenyl groups substituted at the tetrahedral sp3‐carbon bridges, is selected to function as the conjugated breaker that can sterically hinder intermolecular packing to reduce polymers’ crystallinity. A series of donor–acceptor random copolymers is thus developed via polymerizing the crystalline DPP units with the DITT conjugated breakers. By controlling the monomeric DPP/DITT ratios, DITT30 reaches the optimal balance of crystalline/amorphous regions, exhibiting an exceptional power factor (PF) value up to 12.5 µW m−1 K−2 after FeCl3‐doping; while, simultaneously displaying the capability to withstand strains exceeding 100%. More significantly, the doped DITT30 film possesses excellent mechanical endurance, retaining 80% of its initial PF value after 200 cycles of stretching/releasing at a strain of 50%. This research marks a pioneering achievement in creating intrinsically stretchable polymers with exceptional thermoelectric properties. The introduction of a conjugated breaker DITT imparts stretchability to a highly crystalline diketopyrrolepyrrole (DPP)‐based polymer. The doped DITT30 polymer demonstrates an outstanding PF value of up to 12.5 µW m−1 K−2 and exhibits excellent mechanical endurance, retaining 80% of its initial PF value after undergoing 200 cycles of stretching and releasing at a strain of 50%.