“Semi-Random” Multichromophoric rr-P3HT Analogues for Solar Photon Harvesting

Abstract

We introduce a new family of semi-random alkylthiophene-based copolymers, which broadly absorb sunlight due to the randomized incorporation of small amounts of acceptors in the polymer backbone. The so-called semi-random structure is defined by a random polymerization that is based on a restricted linkage pattern of the monomers due to regiospecific placement of the reactive functional groups. As a consequence, the polymers are designed to retain a higher degree of structural order than purely random analogues. We have described a family of semi-random donor-acceptor copolymers based on regioregular poly(3-hexylthiophene) (P3HT). In our preliminary investigations, we have found that the attractive properties of P3HT are retained, and despite the randomized polymerization, semicrystalline polymers with high charge carrier mobilities are realized. In addition, broad and intense spectral absorption is achieved with only a limited content (10-17.5%) of acceptor units in the polymer backbone using a simple polymerization method based on easily synthesized monomers. Rigorous optimization of bulk-heterojunction solar cells based on these promising polymers is underway, along with more detailed characterization of the polymer electronic structures and synthesis of tailored structural analogues.