Browsing by Author "Wu, Ying-Hsien"

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Electroluminescent main-chain copolymers containing phosphorescent benzimidazole-based iridium complexes as copolymerization backbone units or dopants
(2010-06-01)
Huang, Wei-Sheng
;
Wu, Ying-Hsien
;
Lin, Hong-Cheu
;
Lin, Jiann T.
;
材料科學與工程學系
A series of novel electroluminescent main-chain copolymers containing fluorene-1,4-bis(9-octyl-9H-carbarzol-3yl)-2,5-dioctyloxy-benzene (BCB) segments and phosphorescent benzimidazole-based iridium (Ir) complexes in the backbones were synthesized by Suzuki coupling reaction. The relative intensity of phosphorescence and fluorescence were affected by the energy transfer and back transfer efficiencies between the polymer backbones and the iridium units as evidenced by solid state PL and EL spectra. PLED devices with a configuration of TTO/PEDOT: PSS (70 nm)/Ir-copolymers (P3-P10) or Ir-doped copolymers (P1-P2 doped with Ir-complex 4) (60-80 nm)/TPBI (40 nm)/LiF (1 nm)/Al (120 nm) were fabricated, where electroluminescence (EL) efficiencies depended on the chemical constituents and the triplet energies of the copolymers. PLED devices based on Ir-containing copolymer P8 or copolymer P2 doped with 5 mol% Ir-complex 4 exhibited white-light emissions with EL properties of eta(ext,max) = 0.93%, eta(c,max) = 1.88 cd A(-1), and L(max) = 1960 cd m(-2) from the former (P8), and eta(ext,max) = 4.09%, eta(c,max) = 10.94 cd A(-1), and L(max) = 4870 cd m(-2) from the latter (P2 doped with Ir-complex 4), respectively. The CIE coordinates, color-rendering index (CRI) and correlated color temperature (CCT) of the two PLED devices were (0.33, 0.30) at 13 V, 74 and 5966 K for the former, and (0.35, 0.32) at 15 V, 82 and 6147 K for the latter, respectively.
Highly branched green phosphorescent tris-cyclometalated iridium(III) complexes for solution-processed organic light-emitting diodes
(2009-07-01)
Huang, Wei-Sheng
;
Lin, Chia-Wei
;
Lin, Jiann T.
;
Huang, Jen-Hsien
;
Chu, Chih-Wei
A series benzoimidazole-based dendritric complexes of iridium dendrimers containing Frechet-type dendrons with peripheral fluorenyl surface groups have been synthesized. These iridium dendrimers are green-emitting with high phosphorescence quantum yield, and can be spin-coated as films of good quality. From cyclic voltammograms (CV), high onset potentials at 1.42-1.58 V due to the peripheral fluorene group were observed. Device from a second generation dendrimer 17 with structure of ITO/PEDOT:PSS/CBP: 20 wt% 17/TPBI/LiF/Al (PEDOT:PSS = poly(ethylene dioxythiophene): polystyrenesulfonate and CBP = bis(N-carbazolyl)biphenyl) has the best performance: maximum external quantum efficiency of 13.58% and maximum current efficiency of 45.7 cd/A. Space-charge-limited current (SCLC) flow technique was used to measure the mobility of charge carriers in the blend films of the compounds in CBP. Blend films of higher generation dendrimers have lower hole mobility, albeit with higher device efficiencies. (C) 2009 Elsevier B.V. All rights reserved.
Synthesis, characterization, and photophysics of electroluminescent fluorene/dibenzothiophene- and fluorene/dibenzothiophene-S,S-dioxide-based main-chain copolymers bearing benzimidazole-based iridium complexes as backbones or dopants
(2009-11-27)
Huang, Wei-Sheng
;
Wu, Ying-Hsien
;
Hsu, Ying-Chan
;
Lin, Hong-Cheu
;
Lin, Jiann T.
A series of electroluminescent copolymers containing fluorene-2,8-disubstituted dibenzothiophene (PFD), fluorene-2,8-disubstituted dibenzothiophene-SS-dioxide (PFDo) and phosphorescent benzimidazole-based iridium (Ir) complexes in the backbones were synthesized by the Suzuki coupling reaction. The thermal stabilities, HOMO/LUMO levels and triplet energy gap (ET) values were enhanced with increasing contents of dibenzothiophene ( D) or dibenzothiophene-S,S-dioxide (Do) segments in the copolymers. The relative intensities of phosphorescence and fluorescence were affected by the energy transfer and back transfer efficiencies between the polymer backbones and iridium units as evidenced by solid state PL and EL spectra. PLED devices with a configuration of ITO/PEDOT:PSS (50 nm)/metal-free copolymers (P1-P5), Ir-copolymers (P7-P13) and Ir-doped copolymers (P3 doped with Ir-complexes 6 and 8) (60-80 nm)/TPBI (40 nm)/LiF (1 nm)/Al (120 nm) were fabricated, and the electroluminescence (EL) efficiencies depended on the chemical constituents and triplet energies of the copolymers. The space-charge-limited current (SCLC) flow technique was used to measure the charge carrier mobilities of these copolymers, where both hole and electron mobilities were in the following order: the metal-free copolymers (P2, P3 and P5) > Ir-doped copolymers (P3+3 or 10 mol% Ir-complex 6) > Ir-copolymers (P7, P8, P12 and P13). (C) 2009 Elsevier Ltd. All rights reserved.