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Charge-Transporting Polymers based on Phenylbenzoimidazole Moieties



A series of novel styrene functionalized monomers with phenylbenzo[d]imidazole units and the corresponding homopolymers are prepared. These side-chain polymers show high glass-transition temperatures that even exceed the corresponding value for the common electron-transporting material 1,3,5-tris(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBI). Similar electronic behavior between the polymers and TPBI is shown. The polymers are used as matrices for phosphorescent dopants. The fabricated devices exhibit current efficiencies up to 38.5 cd A−1 at 100 cd m−2 and maximum luminances of 7400 cd m−2 at 10 V with a minimum turn-on voltage as low as 2.70 V in single-layer devices with an ITO/PEDOT:PSS anode (ITO = indium tin oxide, PEDOT:PSS = poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate)) and a CsF/Ca/Ag cathode.