Tailoring Charge Transport Properties of Anthracene-Based Polymers by Modification of Thiophene-Based Comonomers

Anthracenes have become a rising star in organic semiconducting materials owing to the high stability and superior mobility. In spite of solution processability for large area fabrication, anthracene-based polymers lag far behind small-molecule counterparts in terms of molecular diversity and carrier mobility. Herein, we synthesized two anthracene-based polymers via Stille reaction by incorporation of two structurally similar units bithophene and cyclopentadithiophene. Anthracene-bithophene alternating polymer (PAnBT) polymer was calculated to take a twisted backbone conformation, showing very poor mobility of 3.6x10-4 cm2 V-1 s-1 with relatively low crystallinity and coarse film morphology. In contrast, anthracene-cyclopentadithiophene alternating polymer (AnCPDT) polymer was calculated to adopt a planar backbone conformation and displayed significantly improved mobility up to 2.2x10-2 cm2 V-1 s-1 with relatively high crystallinity and smooth film morphology, which is one of the highest mobilities for anthracene-based polymers. The different substitution positions of alkyl chains account for the varied polymer backbone conformations, resulting into a big discrepancy in film microstructures and charge carrier mobilities. This work demonstrates that design of planar backbone conformation is beneficial to improve charge transport characteristics for anthracene-based polymers.