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FRET-Assisted Deep-Blue Electroluminescence in Intercalated Polymer Hybrids

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journal contribution
posted on 12.08.2014, 00:00 by Umberto Giovanella, Giuseppe Leone, Francesco Galeotti, Wojciech Mróz, Francesco Meinardi, Chiara Botta
Polymer/layered silicate nanocomposites (PSNs), obtained through a bottom-up strategy with both free and intercalated poly­(styrene) carrying fluorescent terfluorene side-chains, allow for the fabrication of optically transparent films with controlled morphology and fine-tuning of the organic/inorganic interface properties. The successful assessment of the hybrid material as an efficient emitter in a light-emitting device is reported, and the complex mechanism responsible for its emission is elucidated. The approach allows planarization and chemical and photostabilization of short intercalated oligo­(fluorene)­s whose emissive properties are enhanced thanks to exciton localization. Both photoluminescence and electroluminescence are assisted by a sensitization mechanism exploiting resonant energy transfer from nonplanar, nonintercalated polymer pendant conformers wrapping the silicates. A single-layer, solution-processable, hybrid light emitting diode (LED) displays deep-blue electroluminescence with a record external quantum efficiency, for this class of materials, of 1.2%, maximum luminance of 860 cd/m2, Commission Internationale de l’Eclairage (CIE) 1931 (x, y) chromaticity coordinates of (0.158, 0.114), and low efficiency roll-off thanks to the separation of the emissive region from the charge transport one.