RELATIONSHIP BETWEEN STRUCTURE AND ELECTROLUMINESCENCE OF OLIGO(Y-PHENYLENEVINYLENE)S

The preparation of LEDs with poly(p-phenylenevinylene) (PPV) as emitti ng material is well established, However, due to the presence of a dis tribution of conjugated chain lengths in the polymer, systematic inves tigations of the electroluminescence with polymeric materials are diff icult, as far as the optical emission is concerned. We are studying th e relationship between structural variation of substituted oligo(p-phe nylenevinylene)s and their electroluminescent behaviour using a series of distyrylbenzenes with a variety of substituents in order to invest igate their influence on the electroluminescence (EL). Furthermore, we synthesized a homologous series of monodisperse oligo(2,5-dipropoxy-1 ,4-phenylenevinylene)s with up to 11 repeating units. This series cove rs the spectrum from monomer to polymer. The influence on the EL can b e investigated by preparing single layer LEDs using vapor deposition o r spincoating of the oligomers in a polystyrene (PS) matrix. The compa rison of photoluminescence (PL)- and EL-spectra shows that the photoph ysical properties of the oligomers are strongly altered by aggregation phenomena. (C) 1998 Elsevier Science B.V.