  We report a group of unusually big molecular orbitals in the C60/pentacene
complex. Our first-principles density functional calculation shows that these
orbitals are very delocalized and cover both C60 and pentacene, which we call
superintermolecular orbitals or SIMOs. Their spatial extension can reach 1 nm
or larger. Optically, SIMOs are dark. Different from ordinary unoccupied
molecular orbitals, SIMOs have a very weak Coulomb and exchange interaction.
Their energy levels are very similar to the native superatomic molecular
orbitals in C60, and can be approximately characterized by orbital angular
momentum quantum numbers. They have a distinctive spatial preference. These
features fit the key characters of charge-generation states that channel
initially-bound electrons and holes into free charge carriers. Thus, our
finding is important for C60/pentacene photovoltaics.
