Synthesis and properties of hyperbranched fluorescence/phosphorescence hybrid copolymers for white polymer light emitting devices

Abstract A series of hyperbranched fluorescence/phosphorescence hybrid copolymers with 9,9-dioctylfluorene and bis(1-phenyl-isoquinoline)(acetylacetonato)iridium(III) (Ir(piq)2acac) as the branches and the three-dimensional structured spiro[3,3]heptane-2,6-dispirofluorene (SDF, 10 mol %) as the core have been synthesized by adjusting the feeding ratios of Ir(piq)2acac (0.02–0.05 mol %). The copolymers showed good thermal and spectral stability, and amorphous film morphology because of the hyperbranched structures. The 2,7-substituted fluorenes of SDF were incorporated into the π-system of the polyfluorene branches, and remained the Forster resonance energy transfer (FRET) efficiency from fluorene segment to Ir(piq)2acac unit. The copolymers exhibited efficient electroluminescent characters, and white-light emission was achieved in PFSDF-Ir4 (Ir(piq)2acac 0.04 mol %)-based single layer device with CIE coordinates at (0.30, 0.34), a maximum luminance of 6777.3 cd/m2 (at 18.3 V), and a maximum current efficiency of 4.0 cd/A.