Effect of Diffusion on Charge Transport in Organic Photovoltaic Blends

Charge transport is one of the key factors in the operation of organic photovoltaic devices. Non-fullerene acceptor materials have recently attracted significant attention in organic photovoltaics due to their great potential to realize high power conversion efficiencies. In this paper, we investigate the effect of diffusion on charge transport in a variety of binary and ternary organic photovoltaic materials, including both polymer:fullerene and polymer:non-fullerene blends. It is shown that the temperature dependent current density voltage characteristics from the drift-diffusion simulations incorporating the extended Gaussian disorder model (EGDM) are more consistent with experimental data in comparison with those obtained from the only drift model for all these material systems. Furthermore, it is found that the effect of diffusion on charge transport is more pronounced at low voltages and seems to be negligible when the applied voltage exceeds 1 V. The deviation of calculated curves from experimental measurements gradually increases with increasing temperature. It is of great importance to the influence of diffusion effect on charge transport in both polymer:fullerene and polymer:non-fullerene blends.