Endohedral fullerene as acceptor: A DFT study on charge trans- fer states of Sc3N@C80-porphyrin complex

C\textbf{60} fullerene and its derivatives are the most popular acceptors which are used in molecular/polymeric complexes used in organic photovoltaics. Endohedral fullerenes are shown to produce long lived charge separated states. The Sc\textbf{3}N@C\textbf{80}, the third most abundant fullerene after C\textbf{60 }and C\textbf{70}, has a larger cage with a radius of 4.1 Ang. We have carried out a DFT study on the electronic structure of ground and charge transfer states of a model Sc\textbf{3}N@C\textbf{80}-Zn tetraphenyl porphyrin cofacial complex. The C\textbf{80 }cage used in our calculations has icosahedral symmetry. We find that the lowest charge transfer state with a hole on the porphyrin and an electron on the Sc\textbf{3}N@C\textbf{80 }is at 2.1 eV above the ground state. The calculations show that dif- ferent orientations of the Sc\textbf{3}N unit to the porphyrin plane do not significantly alter the electronic structure. The electronic structure of the complex and its components along with the exciton binding energies will be presented.