The Ultrafast Photophysics of Pentacene Coupled to Surface Plasmon Active Nanohole Films

Pentacene, a model organic semiconductor, is shown to couple with surface plasmon (SP) active silver nanohole films to produce enhanced excited-state absorption. In addition, the dynamics of triplet formation and decay on a subpicosecond time scale are altered due to the coupling of the excited state with the resonant SP, possibly involving the interplay between singlet fission and triplet-triplet annihilation. Shifting the resonance of the SP with respect to the pentacene excitations and introducing a dielectric spacer between pentacene and metal lead to changes in the spectra and dynamics that can be explained qualitatively. These results are compared with recent literature reports of molecule/plasmon hybridization and are placed in context with efforts to utilize SPs for enhanced solar energy conversion.