FRET-assisted deep-blue electroluminescence from planar, intercalated oligofluorene side-chains in a new polymer/layered silicate hybrid

A facile and robust approach for fabricating structured, blue-emitting polymer hybrids is explored by grafting poly(styrene) incorporating ?-conjugated terfluorene side-chains, to fluoromica silicate layers through surface-initiated nitroxide-mediated polymerization [1]. The hybrids exhibit blue photoluminescence quantum yield as high as 0.90 in the solid, and significantly enhanced thermal and chemical stabilities with respect to the organic precursors. The successful assessment of the hybrid material as efficient emitter in a light-emitting device is accomplished, and we shed light onto the not straightforward mechanism responsible for its emission. The layered hybrid approach allows us to achieve, at the same time, planarization and chemical and photo- stability of short oligo(fluorene)s whose emissive properties are enhanced thanks to exciton localization. Lying-flat intercalated terfluorene moieties are sensitized by non planar conformers grafted onto the outer polymer chains, that envelop the silicates, through a resonant energy transfer mechanism. Single layer solution processable device displays deep blue electroluminescence with an external quantum efficiency of 1.2 %, maximum luminance close to 1000 cd/m2, chromaticity coordinates of (0.16;0.11) and low efficiency roll-off thanks to the separation of the emissive region from the charge transport one.