Abstract
The synthesis, characterisation, and device performance of a series of cyclopentadithiophene (CPDT)-naphthalenediimide (NDI) donor-acceptor-donor (D-A-D) polymers is reported. The monomers with various alkyl chains are synthesised via direct arylation using palladium complex catalyst. The monomers are then polymerised by oxidative polymerisation using FeCl 3 to provide high molecular weight polymers (M n = 21,800-76,000). The polymer films show deep-red absorption including near-infrared region up to 1100 nm to give optical bandgap of approximately 1.16 eV. The polymers exhibit only n-type semiconducting properties giving the highest electron mobility of 9 × 10 -3 cm 2 V -1 s -1 in organic field-effect transistors (OFETs). Organic photovoltaic (OPV) devices are fabricated from solutions of the polymers as acceptors and poly(3- hexylthiophene) (P3HT) as a donor. © 2014 Elsevier B.V. All rights reserved.