n-Type semiconducting polymers as electron acceptors for organic photovoltaics

The aim of this work is to develop some new polymer materials with typical n-type semiconducting properties and low reduction peak potentials. Therefore new organo-soluble copolyquinoxalines were used in polymer blends with poly-[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenvinylene] or regioregular poly-(3-hexylthiophene). The photovoltaic properties of these polymer blends depend on the blend morphology. So the short circuit current density can be improved by better solvent mixtures and by temper processes. But nevertheless the photovoltaic properties are low and a stable and well ordered phase morphology is difficult to obtain with polymer blend systems. Therefore another approach to receive more effective full polymer photovoltaic cells was done. Block copolymers consisting of n-type and p-type sequences in one polymer chain were synthesized. As n-type material a quinoline monomer and as p-type material 3-hexylthiophene were used. The synthesis of these new materials is described. The spectroscopic and cyclovoltammetric investigations clearly indicate their block copolymer structure. The study of their phase morphology and photovoltaic properties is in progress.