Organic solar cells with sensitized phosphorescent absorbing layers

We demonstrate an increase of the exciton diffusion length (LD) 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, LD increases from 4 ± 1 to 9 ± 1 nm for an optimal doping of 5 wt%. As a result of the increased LD, 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.