Molecular orientations, electronic properties and charge transfer timescale in a Zn-porphyrin/C70 donor–acceptor complex for solar cells

Here we demonstrate that a molecular dye film composed by a single layer of C70 and a single layer of Zn-tetraphenyl-porphyrin (ZnTPP) adsorbed atop can be grown on large substrates using molecular beam epitaxy. The electrostatic interactions between the constituent molecules drive the formation of this ordered donor–acceptor layer. The overlapping between the π∗ orbitals of ZnTPP and C70 allows the delocalisation of the excited electrons from the excited molecule on a timescale of ∼6 fs. Generally, the ZnTPP/C70 film, acting as a p–n junction, delocalise more efficiently the excited electrons as compared to pure ZnTPP films on a timescale that competes effectively against loss processes, suggesting its application for a more efficient solar energy conversion in organic-based devices.