Modelling exciton diffusion in disordered conjugated polymers

We present a combined quantum-chemical and Monte Carlo approach for calculating exciton transport properties in disordered organic materials starting from the molecular scale. We show that traps and energetic disorder are the main limitations for exciton diffusion in conjugated polymers. An analytical model for exciton hopping in a medium of sites with uncorellated energetic disorder gives a quantitative description on the dependence of the diffusion length to both the energetic disorder strength and temperature. We demonstrate how traps and energetic disorder can pin down the diffusion length in conjugated polymers to values below 10 nm.