Accurate measurement of the exciton diffusion length in a conjugated polymer using a heterostructure with a side-chain cross-linked fullerene layer

Exciton diffusion and photoluminescence quenching in conjugated polymer/fullerene heterostructures are studied by time-resolved photoluminescence. It is observed that heterostructures consisting of a spin-coated poly(p-phenylene vinylene) (PPV)-based derivative and evaporated C-60 are ill-defined because of diffusion of C60 into the polymer, leading to an overestimation of the exciton diffusion length. This artifact is resolved by the use of a novel, thermally side-chain polymerizing and cross-linking fullerene derivative (F2D) containing two diacetylene moieties, forming a completely immobilized electron acceptor layer. With this heterostructure test system, an exciton diffusion length of 5 +/- 1 nm is derived for this PPV derivative from time-integrated luminescence quenching data.