Fast predictions of exciton diffusion length in organic materials

Diffusion of singlet excitons is one of the main steps in the working of organic photovoltaic devices. Large diffusion lengths increase the chances of an exciton to arrive at an interface where charge separation may occur. The vast amount of organic compounds available requires a simple computational protocol able to estimate this critical parameter. Here we present a protocol that combines quantum chemistry calculations and analytical considerations to estimate the exciton diffusion lengths of several commonly employed organic molecules under different morphological conditions. The results show a relationship between molecular transition dipole moments and improvements in the diffusion length. Importantly, the protocol requires only knowledge of the molecular structure and also permits the prediction of Forster transfers in heterodimers. The method described here may be a useful tool for the rational design of optoelectronic devices.