Quantum photocell models consisting of two dipole-dipole coupled donors and the acceptor. Solar radiation (ℏνs ) drives transitions between the valence band state |b〉 and the conduction band state |a_i,(i = 1,2)〉. The curve with double arrows represent dipole-dipole coupled interaction between the conduction band state |a_i,(i = 1,2)〉. The dashed curves represent the transferring channels of electrons. Transitions between level |a_i〉_{i = 1,2} ↔ |c〉, |v〉 ↔ |b〉 are connected to a load.