Organic solar cells with sensitized phosphorescent absorbing layers

We demonstrate an increase of the exciton diffusion length (L-D) Of a fluorescent donor layer via the process of sensitized phosphorescence, whereby initially generated singlet excitons are transferred to triplet excitons via a properly chosen dopant molecule. Using a poly(p-phenylene vinylene) host doped with the phosphorescent molecule platinum octaethylporphyrin, L-D increases from 4 +/- 1 to 9 +/- 1 nm for an optimal doping of 5 wt%. As a result of the increased L-D, the photocurrent from the doped layer increases by 40%, By doping with the fluorescent, non-metalated analogue octaethylporphyrin, a reduction in photocurrent is shown, providing further evidence of the sensitized phosphorescence mechanism. (C) 2009 Elsevier B.V. All rights reserved.