Coupling Between a Molecular Charge-Transfer Exciton and Surface Plasmons in a Nanostructured Metal Grating

The interaction of molecular excitons in organic thin films with surface plasmon polaritons (SPPs) in nanostructured metal electrodes represents a unique opportunity for enhancing the properties of the active layer of a photoconversion device. We present evidence of hybridization between charge-transfer excitons (CTEs) in 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and SPP modes in silver grating nanostructures. Molecular and SPP absorption peaks exhibit avoided crossings in angle-dependent reflectivity experiments, which are verified by electromagnetic-field simulations of the PTCDA-grating structure. Photoluminescence measurements indicate that the radiative decay of the CTE is enhanced. Besides energetic resonance, selective coupling between the SPP and the exciton in this unique case may be aided by the oriented nature of PTCDA into 1-D "molecular stacks" as well as the delocalized nature of the CTE.