Synthesis of an Indolocarbazole Based Small Molecule: Towards Donor-Acceptor Type Ladder Polymers

Abstract

The use of donor-acceptor (D-A) type ladder polymers as p-type semiconducting materials in optoelectronic devices has received significant attention recently due to the possibilities of increasing the efficiency of organic solar cell devices, while simultaneously decreasing the cost required for device fabrication. As such, the synthesis of an acceptor-donor-acceptor (A-D-A) type small molecule comprised of indolo[3,2-b]carbazole donor units and benzo[c][1, 2, 5]thiadiazole acceptor units is reported. The structure-property relationships of two types of solubilizing alkyl chains were investigated. The resulting A-D-A small molecule provides a general strategy for the synthesis of indolo[3,2-b]carbazole and benzo[c][1, 2, 5]thiadiazole based D-A ladder polymers, which possess significant potential as an electron donor material for organic photovoltaic devices. The synthesis reported here is a facile and versatile method utilizing Suzuki coupling reactions, followed by highly efficient ring closing metathesis reactions to construct a defect-free small molecule, and in the future, D-A type ladder polymers.