Effect of the controllable molecular ordering in a new polymer on carrier transport and photovoltaic properties

The functionalized soluble poly(p-phenylene vinylene) derivative bearing polar molecules (nlo-ppv) was designed and synthesized to investigate effects of molecular orientation in single-layer polymer photovoltaic devices. The active molecule is the 4-(n-butyl-n-2-hydroxyethyl)-1-nitro-benzene group on the copolymer. The grafting of the molecule with a donor/transmitter/acceptor structure, possessing a large ground state dipole moment, enables their orientation by a dc-electric field. An internal electric field in such layer facilitates exciton dissociation and improves charge transport. We report increase of the external quantum efficiency by a factor of 1.5 to 2 upon orientation. The associated effects on the carrier injection and transport depending on the orientation direction were evidenced.