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Ho C.-L.,Hong Kong Baptist University | Ho C.-L.,University Grants Committee of | Chi L.-C.,National Taiwan University | Hung W.-Y.,National Taiwan Ocean University | And 9 more authors.
Journal of Materials Chemistry | Year: 2012

The synthesis, isomerism, photophysics and electrophosphorescent characterization of some functional cyclometallated iridium(iii) complexes containing 2-[2-(N-phenylcarbazolyl)]pyridine and 2-[3-(N-phenylcarbazolyl)] pyridine molecular frameworks are described. A carbazole-based coplanar molecule (CmInF) obtained through the intramolecular ring closure of aryl substitutions at the C3 and C6 positions exhibits a high triplet energy (ET = 2.77 eV), morphological stability (Tg = 195 °C) and hole mobility in the range of up to 5 × 10-3 cm2 V-1 s-1. Highly efficient multi-color electrophosphorescent devices have been successfully achieved employing CmInF as the universal host material doped with phosphorescent dopants of various colors under the same device configuration of ITO/PEDOT:PSS (300 Å)/TCTA (250 Å)/CmInF: dopant (250 Å)/TAZ (500 Å)/LiF/Al (PEDOT:PSS = poly(ethylene dioxythiophene):polystyrene sulfonate; TCTA = 4,4′,4′′-tri(N- carbazolyl)triphenylamine; TAZ = 3-(4-biphenylyl)-4-phenyl-5-(4-tert- butylphenyl)-1,2,4-triazole). Through the mixing of two phosphorescent dopants of complementary colors, we also fabricated a two-color white organic light-emitting device (WOLED) with the same device structure consisting of 12 wt% FIrpic and 0.3 wt% (Mpg)2Ir(acac) co-doped into CmInF as a single-emitting-layer, which exhibits peak WOLED efficiency of 13.4% (23.4 cd A-1) and 11.2 lm W-1 with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.33, 0.37). In addition, the use of such device structure in full-color OLEDs has the advantages of simplifying manufacturing process and reducing production cost that are the critical issues of commercialization. Source

Chen S.,Hong Kong University of Science and Technology | Chen S.,University Grants Committee of | Tan G.,Hong Kong Baptist University | Tan G.,University Grants Committee of | And 4 more authors.
Advanced Functional Materials | Year: 2011

A novel yellowish-green triplet emitter, bis(5-(trifluoromethyl)-2-p- tolylpyridine) (acetylacetonate)iridium(III) (1), was conveniently synthesized and used in the fabrication of both monochromatic and white organic light-emitting diodes (WOLEDs). At the optimal doping concentration, monochromatic devices based on 1 exhibit a high efficiency of 63 cd A -1 (16.3% and 36.6 lm W-1) at a luminance of 100 cd m -2. By combining 1 with a phosphorescent sky-blue emitter, bis(3,5-difluoro-2-(2-pyridyl)phenyl)-(2-carboxypyridyl)iridium(III) (FIrPic), and a red emitter, bis(2-benzo[b]thiophen-2-yl-pyridine)(acetylacetonate) iridium(III) (Ir(btp)2(acac)), the resulting electrophosphorescent WOLEDs show three evenly separated main peaks and give a high efficiency of 34.2 cd A-1 (13.2% and 18.5 lm W-1) at a luminance of 100 cd m-2. When 1 is mixed with a deep-blue fluorescent emitter, 4,4′-bis(9-ethyl-3-carbazovinylene)-1,1′-biphenyl (BCzVBi), and Ir(btp)2(acac), the resulting hybrid WOLEDs demonstrate a high color-rendering index of 91.2 and CIE coordinates of (0.32, 0.34). The efficient and highly color-pure WOLEDs based on 1 with evenly separated red, green, blue peaks and a high color-rendering index outperform those of the state-of-the-art emitter, fac-tris(2-phenylpyridine)iridium(III) (Ir(ppy)3), and are ideal candidates for display and lighting applications. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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