Nano graphite platelets enhanced blue emission in alternating current field induced polymer based electroluminescence devices using Poly (9,9-dioctylfluorenyl-2,7-diyl) as the emitter

We report a simple way of enhancing blue emission in Poly (9,9-dioctylfluorenyl-2,7-diyl) (PFO) based alternating current field driven electroluminescence devices by mixing graphite nano platelets in the emission layer. Significantly strong and well resolved blue peaks at 437 nm and 470 nm are observed both in the devices' electroluminescence and photoluminescence spectra with the presence of graphite nano platelets. The origin of this strong blue emission has been identified as the PFO's beta-phase formation confirmed by transmission electron microscopy images and UV-Vis absorption spectra. The nano platelets loading in PFO solution can be controlled by the dispersion time in organic solvents. When the loading increases, the green emission in the electroluminescence spectrum can be reduced. This technique has been found useful in the generation of bright white light when illuminating through down conversion phosphor.