The role of diffusion of excitons in organic photorefractive materials

Abstract

A theory of photorefractive (PR) effect in organic PR materials based on exciton formation, diffusion, and dissociation in organic polymer semiconductors is presented. The exact numerical and approximate analytical solutions of the model indicate that an increase in the exciton diffusion constant reduces the amplitude of the resulting space-charge electric field. The model also shows that a space-charge field is produced even in the absence of traps, and particular combinations of the detrapping rates and the trap depths could be used to enhance the space-charge field. It is suggested that an organic semiconductor with a smaller exciton diffusivity and traps with optimal detrapping rates would be a better candidate for photorefractivity.