Synthesis and characterization of poly(carbazolyl-2,7-vinylene) derivatives for organic light-emitting diode applications

Novel electroluminescent polymers, poly[N-(3,4-bis(decyloxy)phenyl)carbazolyl-2,7-vinylene)] (PCzV) and poly[N-(3,4-bis(decyloxy)phenyl)carbazolyl-2,7-vinylene)-co-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene}] (PCzV-co-MEH-PPV), which is a series of fully conjugated poly(N-dialkoxyphenylcarbazolyl-2,7-vinylene) derivatives with meta- and para-decyloxy phenyl moieties as a pendant group, were synthesized using the Gilch polymerization method. The resulting polymers were highly soluble in common organic solvents and could be easily spin-coated onto an indium-tin oxide coated glass substrate to obtain high quality optical thin films. The weight-average molecular weight (Mw) and polydispersity of PCzV and PCzV-co-MEH-PPV were 3.86×104 and 1.60 and 7.99×104 and 2.05, respectively. Organic light-emitting diodes (OLEDs) were fabricated with the following structures: ITO/PEDOT:PSS/emitting polymer/cathode configurations using either double-layer Ba/Al or triplelayer tris(8-hydroxyquinolinato)aluminum (Alq3)/LiF/Al cathode structures. The maximum brightness and current efficiency were 5,965 cd/m2 and 0.43 cd/A at 10 V.