Polymer electrophosphorescent device: comparison of phosphorescent dye doped and coordinated systems

Abstract

We have synthesized a new polymer, (poly(Ir(ppy)(2)(2-(4-vinylphenyl)pyridine))-co-vinylcarbazole)) [Ir complex copolymer], containing both carbazole and iridium(III) complex as side groups and fabricated electrophosphorescent polymer light emitting devices. The (MLCT)-M-1 transition of Ir complex copolymer is almost same position and absorption intensity of 8% Ir(ppy)(3) doped PVK. At a lower molar concentration of the Ir complex copolymer, the polymer exhibited emission only from the carbazole units. However, with gradual increase in the concentration of the Ir complex copolymer, emission from the Ir complex became dominant. Present results indicated the energy transfer takes place by the intermolecular energy transfer not the intramolecular energy transfer. From the PL and EL of film state, the emission maximum was observed at 512 nm, due to the radiative decay from the (MLCT)-M-3 state to the ground state, confirming almost a complete energy transfer from carbazole to Ir complex. The device showed 4.4% maximum external quantum efficiency and 5.0 lm/W power efficiency and peak luminance of 12,900 cd/m(2). (C) 2002 Elsevier Science B.V. Alt rights reserved.