Synthesis and electro-optical properties of electroluminescent polymers containing carbazole unit

A new series of the processable emissive polymers containing dialkylphenylene vinylene and N-ethylcarbazole units was synthesized by Wittig polymerization. The resulting polymers are soluble in organic solvents and spin-cast to make a thin film. A light emitting diode (LED) was fabricated by sandwiching the emissive polymers between indium-tin oxide and aluminum electrodes. Strong emission at 460 and 490 nm were observed from the devices made by the synthesized polymers. The present polymers have the strong absorption band at around 310 nm, which are due to the π–π∗ transition of the conjugated segments of corresponding polymers. I–V curve shows typical rectifying diode characteristics. The forward bias turn-on voltage for the LEDs are 5 V for poly(dihexylPV-Cvz) and 10 V for poly(MEHPV-Cvz), respectively.