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novel bipolar copolymer combining hole-transporting units, electron-transporting units and light-emitting units (Alq) had been synthesized via free radical copolymerization of N-vinylcarbazole and Alq monomer containing phenothiazine group. The chemical structure and composition of the copolymer were characterized by H NMR, C NMR, FT-IR spectroscopy, and elemental analysis as well as gel permeation chromatography (GPC). The number-average molecular weight ( M) and polydispersity of these copolymers with different Alq contents were around 20000 and 1.4, respectively. The DSC and TGA measurements indicated that the copolymer has excellent thermal stability and high glass transition temperatures ( T). The optical properties of the copolymer in solution and solid state were investigated by UV-vis and photoluminescence (PL) spectra. Additionally, the effects of Alq content, concentration, excitation wavelength and solvent on PL spectra were studied and the results indicated that there exists efficient energy transfer in the process of photoluminescence. The introduction of carbazole and phenothiazine, as hole-transporting groups and energy transfer stages, provides an effective way to improve carries transporting property and energy transfer efficiency, consequently improving luminescence properties of Alq-based copolymer. [ABSTRACT FROM AUTHOR]

Abstract: A series of bipolar copolymers containing quinoline aluminum moieties and N-vinylcarbazole segments exhibited excellent photoluminescence performance and improved hole-transporting ability, were used as light-emitting materials to fabricate polymeric light-emitting devices (PLEDs). Six simple devices with structure of ITO/PEDOT (40nm)/copolymer (80nm)/CsF (1.5nm)/Al (120nm) were fabricated by solution spin-coating. These devices gave dominant yellow-green emission from quinoline aluminum with excellent stability. Together with electrochemical data, the electroluminescence (EL) mechanism of the devices was studied. Moreover, effects of substituted group and quinoline aluminum''s content on the EL properties of the devices were investigated in detail. The results indicate that the device based on the copolymer (P2-1) with substituted group of carbazole and 2mol% quinoline aluminum possess optimal EL properties with a maximum luminance of 487cd/m2 and a peak current efficiency of 0.545cd/A. [Copyright &y& Elsevier]