Optical and electroluminescent properties of novel poly(aryl ether)s with isolated carbazole and p-quaterphenyl fluorophores

We report the optical and electroluminescent properties of four novel poly(aryl ether)s (P1-P4) consisting of alternate isolated hole-transporting [carbazole or 3,6-bis(styryl)carbazole] and electron-transporting [dicyano-p-quaterphenyl or bis(trifluoromethyl)-p-quaterphenyl] fluorophores. The photoluminescence (PL) spectra of the four polymeric films show maximum peaks around 407-413 nm for P1, P2 and 442447 nm for P3, P4. The PL spectra of P1similar toP4 are dependent on the composition of the two isolated fluorophores. According to the observation of relative quantum yield in poor solvent (cyclohexane), P2 containing more bulky trifluoromethyl groups in p-quaterphenyl segments prevented aggregate quenching processes more than P1. Compared with P1 and P2 with carbazole segments, P3 and P4 with 3,6-bis(styryl)carbazole segments exhibited less interchain interaction and a low threshold electric field in a single-layer device. The p-quaterphenyl and carbazole [or 3,6-bis(styryl)carbazole] segments were regarded as electron-transporting and hole-transporting units, respectively, in the single-layer light-emitting diodes (Al/P1-P4/ITO). In the double-layer device (ITO/MEH-PPV/P2/Al), the maximum luminance was doubled, and the threshold electric fields diminished because P2 functioned as an electron-transporting and hole-blocking layer. Furthermore, the voltage-tunable multicolor emission from orange to green was observed. (C) 2003 Wiley Periodicals, Inc.