Electroluminescent orthofused thiophene dye embedded in polyvinylcarbazole

The photoluminescence and electroluminescence of a molecular precursor of helicene embedded in an active matrix formed by a hole-transporter polymer mixed with an electron transporter molecule are reported. Optimization of the weight ratio between the dye and the matrix is performed by a detailed study of the absolute emission efficiencies obtained by photoexcitation and by charge injection. A 0.17% by weight dye concentration gives the best compromise among energy transfer, transport properties and quenching effects induced by dye aggregation, leading to an external blue electroluminescence efficiency of 0.4% in a single layer device.