A tailorable Au–TiN hybrid plasmonic nanocomposite with tunable optical functionality has been demonstrated.

No abstract

This work presents an experimental investigation of enhancing surface plasmon polariton coupling to semiconductor emission by tailoring metal film thickness.

Organometallic phosphors are an important class of emissive materials used in high-efficiency organic light-emitting devices. However, problems of low photostability arise for blue-emitting phosphors due to chemical and environmental degradation, and to triplet quenching processes. Various approaches have been developed to improve the photostability of such phosphors including development of new organometallic molecules and control of host-dopant composition in thin films. Here, we demonstrate a different approach to improving the photostability of blue organometallic phosphors that uses localized surface plasmon resonances to increase the triplet recombination rate. The increased recombination rate improves the photostability of the phosphor due to the reduction in triplet quenching pathways. We show that the lifetime of phosphorescence is decreased significantly by nanoparticle-based plasmonic surfaces, which improves the photostability of the blue organometallic phosphor by up to a factor of 3.6. Other plasmonic surfaces are also tested and exhibit less significant photostability improvements due to reduced spectral overlap of the plasmonic modes with the emitter and lower mode confinement. The use of plasmonic surfaces to improve phosphor photostability at blue wavelengths is distinct from other approaches because it involves modification to the local electromagnetic environment of the phosphor rather than modifications to the phosphor molecular structure or to the emitting material composition.

Phosphorescence from heavy-atom-free organic conjugated molecules is weak at room temperature due to the low probability of radiative recombination from the triplet state. In this study, the relative intensity of phosphorescence compared to fluorescence from a room-temperature, dual-emission organic molecule N,N′-bis­(1-naphthalenyl)-N,N'-bis­(phenyl)­benzidine doped in a poly­(9-vinylcarbazole) matrix on different plasmonic surfaces is investigated. A variety of different plasmonic surfaces are used to modify the ratio of phosphorescence to fluorescence: discrete Ag nanoparticle layers; discrete Au nanoparticle layers; porous Ag films; porous bimetallic Au/Ag films. The scattering of plasmonic surfaces is tuned to overlap with either the shorter wavelength fluorescence emission of the organic molecule or the longer wavelength phosphorescence emission of the organic molecule by employing metal layers with different compositions. An enhanced relative intensity of phosphorescence is experimentally observed from the organic molecular films on plasmonic surfaces compared to that on glass and planar metallic surfaces. Two mechanisms, radiative decay rate modification and excitation enhancement in the polymer host, are hypothesized to account for the relative phosphorescence intensity enhancement. The results indicate that plasmonic structures can not only enhance the absolute fluorescence/phosphorescence of luminescent materials, as reported by many previous studies, but also modify the relative weight of phosphorescence compared to fluorescence of a heavy-atom-free organic molecules at room temperature. The findings of this work demonstrate that plasmonic surfaces can be used as an external method to manipulate triplet emission from heavy-atom-free organic molecules.