Ground and excited state properties of dye attached fullerenes

C$_{60}$ fullerene and its derivatives are the most popular acceptors which are used in molecular/polymeric complexes used in organic photovoltaics. We have studies C60 molecule functionalized with two dye molecules: DPP and TBTDT. Using density functional theory and large polarized all electron Gaussian basis, we optimized the structures of the C$_{60}$-DPP and C$_{60}$-TBTDT molecules. The electronic structure of C$_{60}$ changes upon functionalization with the dye molecules. The electron affinity of the functionalized fullerene increases. The optical spectra of the functionalized molecules will be presented. Inspection of molecular orbitals of these systems indicates that the HOMO level is localized on the dye whereas the LUMO is on the C$_{60}$ molecule. We have also calculated several lowest CT excited states where the charge transfer takes place from the HOMO on the dye to the LUMO on the C$_{60}$ molecule.