Efficient blue light emission in crosslinked poly(fluorene) multilayer devices

Triple layer light emitting diodes (LEDs) are fabricated from hole transporting crosslinked aryl amine polymers and an emissive polyfluorene homo and copolymers with an oxadiazole electron transporting layer are fabricated using solution spin casting techniques. Most of the triple layer devices are deep blue in color, show high efficiencies and luminances and low operating voltages. Results are interpreted in terms of balanced charge injection and charge blocking leading to greater recombination efficiencies. The maximum external efficiencies for most of the 3-layer devices exceed 1%.