Time filter

Source Type

Chen S.,Hong Kong University of Science and Technology | Chen S.,University Grants Committee of HKSAR | Tan G.,Hong Kong Baptist University | Tan G.,University Grants Committee of HKSAR | 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.


Ho C.-L.,Hong Kong Baptist University | Ho C.-L.,University Grants Committee of HKSAR | 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.

Loading University Grants Committee of HKSAR collaborators
Loading University Grants Committee of HKSAR collaborators