Orange and red emitting OLEDs based on phenothiazine polymers

Abstract

Two novel polymers PQP(poly(3, 7-N-octyl phenothiozinyl cyanoterephthalylidene)) and PQM (poly(3, 7-N-octyl phenothiozinyl cyanoisophthalylidene)) containing phenothiazine were synthesized for application in red and orange light-emitting diodes. The synthesized polymers were characterized using UV-visible, photoluminescence and electroluminescence (EL) spectroscopy. The single-layer EL devices of indium tin oxide(ITO)/PQP(or PQM)/Mg : Ag and multi-layer devices of ITO/PQP(or PQM): N, N′-diphenyl-N, N′-bis(3-methylphenyl) -[1, 1′-biphenyl]-4, 4′ -diamine(TPD) (44 nm)/2, 9-dimethyl-4, 7-diphenyl -1, 10-phenanthroline (BCP, 5 nm)/tris(8-hydroxyquinolinato) aluminium(AlQ3, 20 nm)/Mg : Ag were fabricated. The EL spectra from the devices based on PQP peaked at the wavelength of 664 nm and covered red and infrared regions. The maximal brightness was measured to be about 60 cd m−2 at the applied voltage of 17 V. The devices based on PQM gave bright orange light-emission peaking at 608 nm and the maximal luminance was 150 cd m−2 at the applied voltage of 14 V.