Figure 8 Structure for high-efficiency (50%) organic PV cell based
on a nanostructured substrate onto which thin layers of molecular
multi-junctions are grown and anchored onto the nanostructure
surface. The red circle denotes an electron acceptor; the blue square,
an electron donor; and the yellow circle, a metal nanoparticle.Figure 9 Down-conversion of incident solar photons splits the energy of high-energy photons into two
photons of lower energy that can then be absorbed in the PV device more closely matched to the band gap
energy and thus avoid thermalization (i.e., heating) losses. Up-conversion adds the energies of two lower-
energy incident photons that otherwise would pass through the PV device to produce a single, higher-
energy photon that is equal to or greater than the band gap and can therefore be absorbed.