Vibronic couplings in derivatives for organic photovoltaics

Vibronic coupling constants (VCCs) and reorganisation energies of C 60 derivative anions including [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) are evaluated. The results are analysed in terms of the vibronic coupling density. As long as the electronic state is conserved, the VCCs are similar to those in C 60 - . The VCCs are large when (1) the distribution of LUMO is large around the substituent or (2) the structure of the orbital is significantly changed by the symmetry lowering, which would be unsuitable for an organic photovoltaic material from the viewpoint of vibronic couplings.