Design, Synthesis, and Characterization of a Novel c-Donor-nc-Bridge-cAcceptor Type Block Copolymer for Optoelectronic Applications

A novel conjugated block copolymer system containing a donor-type conjugated block (c-D) covalently connected to an acceptor type conjugated block (c-A) via a nonconjugated and flexible bridge chain (nc-B), also called a DBA type block copolymer, has been designed, synthesized, and characterized for potential cost-effective and high-efficiency optoelectronic applications such as solar cells. Specifically, D is a regio-regular para-2-ethylhexyloxy-substituted polyphenylenevinylene (or EH-RO-PPV), A is a regio-regular polyphenylenevinylene with sulfone (SO2) acceptor moiety and a linear oxydecane (-OC10H21) group substituted on every phenylene unit, and B contains an aliphatic chain with two or four methylene units. The size of each block can be controlled via synthetic feed ratio of the monomer and the terminator. The measured average molecular weights of D, A, and DBA based on gel permission chromatography are in good agreements with the molecular weights calculated using the monomer:terminator synthetic feed ratios. Preliminary optoelectronic device studies revealed an order of magnitude better improvement in photoelectric power conversion efficiency of DBA over the corresponding D/A blend under identical fabrication and testing conditions. Such improvements could be attributed to more efficient photo induced charge separation and charge transport in DBA versus in D/A blends. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1149-1160