Plasmon resonance energy transfer and plexcitonic solar cell.

Plasmon-mediated energy transfer is highly desirable in photo-electronic nanodevices, but the direct injection efficiency of "hot electrons" in plasmonic photo-detectors and plasmon-sensitized solar cells (plasmon-SSCs) is poor. On another front, Fano resonance induced by strong plasmon-exciton coupling provides an efficient channel of coherent energy transfer from metallic plasmons to molecular excitons, and organic dye molecules have a much better injection efficiency in exciton-SSCs than "hot electrons". Here, we investigate enhanced light-harvesting of chlorophyll-a molecules strongly coupled to Au nanostructured films via Fano resonance. The enhanced local field and plasmon resonance energy transfer are experimentally revealed by monitoring the ultrafast dynamical processes of the plexcitons and the photocurrent flows of the assembled plexciton-SSCs. By tuning the Fano factor and anti-resonance wavelengths, we find that the local field is largely enhanced and the efficiency of plexciton-SSCs consisting of ultrathin TiO2 films is significantly improved. Most strikingly, the output power of the plexciton-SSCs is much larger than the sum of those of the individual plasmon- and exciton-SSCs. Our observations provide a practical approach to monitor energy and electron transfer in plasmon-exciton hybrids at a strong coupling regime and also offer a new strategy to design photovoltaic nanodevices.