Blue electroluminescent properties of poly(N-arylcarbazole-2,7-ylene) homopolymers

To investigate electroluminescence behaviors of a series of poly(N-phenyl-2,7-carbazole)s having 2-ethylhexyloxy (PEHOC), triethylene oxide (PTEOC), or diphenylamino (PDPAC) group at the N-phenyl portion, single-layer devices of organic light-emitting diode using the as-prepared polymer as the emitting layer material were fabricated. All the devices showed brightness above 1000cd∕m2 at 10V with moderate luminous efficiencies. The PEHOC (m, p-disubstituted) and PTEOC (p-substituted) devices exhibited a trivial but undesirable redshift due to electro-oxidation and aggregation of the polymer under high driving voltages, while the PDPAC (m-substituted) device displayed a blue electroluminescence [λmax=450nm and CIE (x,y)=0.159,0.173] which had no difference compared with the photoluminescence spectrum.