Cyano-Functionalized Fused Bithiophene Imide Dimer-Based n-Type polymers for High-Performance Organic Thermoelectrics.

Doped n-type polymers usually exhibit low electrical conductivities and thermoelectric power factors (PFs), restricting the development of high-performance p-n junction-based organic thermoelectrics (OTEs). Herein we report the design and synthesis of a new cyano-functionalized fused bithiophene imide dimer (f-BTI2), CNI2, which synergistically combines the advantages of both cyano and imide functionalities, thus leading to substantially higher electron deficiency than the parent f-BTI2. On the basis of this novel building block, a series of n-type donor-acceptor and acceptor-acceptor polymers were successfully synthesized, all of which show good solubility, deep-lying frontier molecular orbital levels, and favorable polymer chain orientation. Among them, the acceptor-acceptor polymer PCNI2-BTI delivers an excellent electrcial conductivity up to 150.2 S cm -1 and a highest PF of 110.3 μW m -1 K -2 in n-type OTEs, attributed to the optimized polymer electronic properties and film morphology with improved molecular packing and higher crystallinity assisted by solution-shearing technology. The PF value is the record of n-type polymers for OTEs to date. This work demonstrates a facile approach to designing high-performance n-type polymers and fabricating high-quality films for OTE applications. This article is protected by copyright. All rights reserved.