Exciton diffusion and dissociation in conjugated polymer/fullerene heterostructures

Time-resolved luminescence spectroscopy has been used to investigate exciton diffusion in thin films of poly(p-phenylene vinylene) (PPV) based derivatives. Exciton density distribution upon photoexcitation in polymer/fullerene heterostructures has been modeled and exciton diffusion length values of 5 nm and 6 nm are estimated for two different PPV derivatives, which differ by three orders of magnitude in charge carrier mobility due to reduced energetic disorder. Hence, the exciton diffusion length is not correlated to the charge carrier mobility in this class of materials.