Synthesis of carbazole-containing PPV and its application to the electroluminescent devices

Carbazole-containing PPV (CC-PPV) was chemically synthesized and demonstrated to be electroluminescent for application to a light emitting diode (LED). Soluble CC-PPV copolymer was prepared from dialdehyde monomer and diphosphonium salt in a mixed solvent (ethanol/chloroform) by the well-known Wittig reaction. The UV–Vis absorption spectrum of CC-PPV copolymer in chloroform has a maximum absorption wavelength at 408 nm, which is caused by the π–π* transition of the conjugated system. In PL spectrum, maximum wavelength of emission was found at 512 nm. From the thermogravimetric analysis (TGA) it was confirmed that the synthesized CC-PPV has a thermal stability up to 180°C. For the fabrication of a LED, the synthesized CC-PPV was dissolved in toluene to prepare an 1.0 wt% solution and the film cast from this solution was demonstrated to be light-emitting at an applied voltage of 3.7 V.