Exciton diffusion length and charge mobility in donor and acceptor materials in organic photovoltaics: Tetrabenzoporphyrin and silylmethyl[60] fullerene

Exciton diffusion length and charge mobility in donor and acceptor materials are important factors for the energy conversion efficiency of organic voltaics. Here, we theoretically analyze these quantities for tetrabenzoporphyrin (BP) and silylmethyl[60] fullerene (SIMEF) that have been exploited for the donor and acceptor of interpenetrating heterojunction organic solar cells. The exciton diffusion length and the charge mobility are calculated by means of density functional theory (DFT) and Fermi's golden rule. The exciton diffusion length in the BP single crystal is found to be a few hundred nm. The charge mobility in the BP and SIMEF crystals exhibits a significant anisotropy.