Singlet exciton diffusion in MEH-PPV films studied by exciton–exciton annihilation

We report time-resolved photoluminescence studies in MEH-PPV films for a wide range of excitation intensities. The results fit well to a diffusion-limited exciton–exciton annihilation model with an annihilation constant γ = (2.8 ± 0.5) × 10−8 cm3 s−1. This enables us to estimate the exciton diffusion coefficient to be D = (3 ± 1) × 10−3 cm2 s−1. This corresponds to a diffusion length between 5 and 8 nm for one-dimensional diffusion.