The optical, electronic, and electroluminescent properties of novel poly(p-phenylene)-related polymers

A variety of novel, soluble, conjugated PPP- and PPV-related polymers have been synthesized using a synthetic approach that allows for the tailoring of the chemical structure of the polymer backbone. The absorption and emission properties of the materials can be tuned over a wide range of the visible spectrum. The materials were characterized in terms of molecular weight and phase behavior. The localization of the energy levels of the polymers has been determined with quantum mechanical calculations and experimentally with optical methods and cyclovoltametry. The mobilities of charge carriers measured in the microwave conductivity experiment are on the order of 10^-7 m²/(V·s) with an activation energy of ca. 0.06 eV. Photoluminescence (PL) quantum yields in solution are generally higher than 60%; in the solid state values even of up to 73% are observed. If the conjugation is interrupted every tenth phenyl unit, mobilities are reduced by a factor of about 2 and PL efficiences are significantly increased. A range of electroluminescent devices partly containing additional electron- and hole-transporting layers were also investigated. We obtain internal EL efficiencies of up to 4% in the blue region.