Ultrafast and Long-Range Energy Transfer from Plasmon to Molecular Exciton

By using a model interface consisting of a metallic grating and zinc phthalocyanine (ZnPc) molecules, we temporally and spatially resolve the energy transfer process from plasmon to molecular exciton via the plasmon-induced resonance energy transfer mechanism. It is found that the energy transfer can occur within 30 fs for a distance of 20 nm. The energy transfer range is much larger than that of typical hot carrier transfer and molecule-to-molecule energy transfer processes. Hence, this ultrafast and long-range plasmon-induced energy transfer channel is especially useful for boosting the exciton/free carrier generation yield in semiconductor layers. Moreover, the enhancement in the exciton production yield does not diminish even when the photon energy is lowered toward the optical absorption edge of ZnPc. Therefore, the observed energy transfer process can extend the optical absorption to frequencies below the optical bandgap of the molecule.