Exciton transport in organic dye layers for photovoltaic applications.

Abstract The mean free path length for excitons was determined in flat organic dye films. From simulations of the photocurrent response of solar cells, consisting of n-type perylene tetracarboxy diimide and a p-type organic dye, we found an exciton diffusion length of 30±10 nm for zinc phthalocyanine (ZnPc), and 7±3 nm for zinctetra-(octylphenyl)-porphyrin (ZnTOPP). The value for ZnTOPP was independently confirmed by the luminescence quenching observed in ZnTOPP layers doped with a variable concentration of quenchers. The results show the direct correlation between the photovoltaic yield of a macroscopic device and the process of energy migration on a molecular scale.