Universal description of exciton diffusion length in organic photovoltaic cell.

A physical model of exciton diffusion length in organic photovoltaic cell based on percolation theory and Forster resonant transfer rate is presented here. The calculated results show a good agreement with Monte Carlo simulation and experimental data, indicating that the proposed model can well describe the temperature and material disorder dependences of exciton diffusion length. More importantly, the effect of carrier density on the exciton diffusion length can also be discussed based on our model, specifically, more intensive light illumination will lead to larger exciton diffusion length. Furthermore, according to our analysis, the Gaussian distribution density of states (DOS) can be well replaced by an exponential DOS at certain exciton concentration, which would help us get an analytical model for the exciton diffusion length. [ABSTRACT FROM AUTHOR]