Browsing by Author "Hwang, SW"

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Color-saturated and highly efficient top-emitting organic light-emitting devices
(2005-05-01)
Hsu, SF
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Lee, CC
;
Hwang, SW
;
Chen, HH
;
Chen, CH
Color-saturated and highly efficient top-emitting organic light-emitting devices (OLEDs) were developed. The device structure studied was glass/reflective silver/indium-tin oxide (ITO; 50, 75, 100, 125 and 150 nm, respectively)/organic electroluminescent (EL) stack/calcium (200 angstrom)/ silver (150 angstrom). By changing the thicknesses of ITO from 50-150 nm in the reflective ITO/Ag anode, different emissive colors from bluish green to orange can be obtained from aluminum tris(8-hydroxyquinoline) (Alq(3)) emitter. By using 2-{2-(t-butyl)-6-[(E)-2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinoline-9-yl)-1-ethenyl]-4H-4-pyranliden}malonitrile (DCJTB), 10-(1,3-benzothiazol-2-yl)- 1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H, 11H-pyrano[2,3-f]pyrido[3,2,1-ij]quinoline-11-one (C-545T) and p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-ph) as dopants, highly saturated red, green, and blue (RGB) emissions with Commission Internationale de L'Eclairage chromaticity coordinates of (0.64, 0.36), (0.14, 0.75) and (0.14, 0.08) were obtained, respectively. (c) 2004 Elsevier B.V. All rights reserved.
Effects of substrate treatment on the electroluminescence performance of flexible OLEDs
(2004-11-01)
Lee, SN
;
Hsu, SF
;
Hwang, SW
;
Chen, CH
;
友訊交大聯合研發中心
Electroluminescence (EL) performance of flexible organic light-emitting device (FOLED) has been found to be highly dependent upon the morphology of the surface of the indium thin oxide (ITO)/plastic substrate as well as the patterning and processing conditions of the substrate. We will present evidence showing that luminance efficiency of FOLED can be greatly improved by pretreatment. Surface analysis of the ITO/PET by means of atomic force microscope (AFM) and optical microscope will be compared with that of the ITO/glass and the influence of flexible OLEDs substrate treatment by various methods on EL performance will also be discussed. (C) 2004 Elsevier B.V. All rights reserved.
Efficient white organic light emitting devices with dual emitting layers
(2005-09-22)
Wu, YS
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Hwang, SW
;
Chen, HH
;
Lee, MT
;
Shen, WJ
In this paper, a new white organic light-emitting device (OLED) with the structure of indium tin oxide/CFx/1,4-bis[N-(1-naphthyl)-N'-phenylamino]-biphenyl (NPB) (30 mn)NPB: 2,8-di(t-butyl)-5,11-di[4-(t-butyl)phenyl]-6,12-diphenylnaphthacene (20 nm; 1.6 %)/2-methyl-9,10-di(2-naphthyl) anthracene: p-bis(p-NN-di-phenyl-aminostyryl)benzene (40 nm, 3%)/aluminum tris(8-hydroxyquinoline) (20 nm)/LiF (1 nm)/Al (200 mn) has been investigated. The device showed white emission with a high-luminous yield of 9.75 cd/A at 20 mA/cm(2), but its Commission Internationale de l'Eclairage chromaticity coordinates appeared to change from (0.34, 0.42) at 6 mA/cm(2) to (0.27, 0.37) at 200 mA/cm(2) due to the shift of recombination zone. The change of color with drive current was suppressed by introduction of an electron-blocking layer of NPB along with a hole-blocking layer of aluminum (III) bis(2-methyl-8-quinolinato)4-phenylphenolato to the white OLED which successfully confined the recombination site and achieved a luminous yield of 9.9 cd/A at 20 mA/cm(2). (c) 2005 Elsevier B.V All rights reserved.
High-efficiency organic electroluminescent device with multiple emitting units
(2004-09-01)
Chang, CC
;
Hwang, SW
;
Chen, CH
;
Chen, JF
;
電子物理學系
In this paper, we report on the fabrication of multilayer organic light emitting diodes (OLEDs) with high electroluminescent (EL) yield achieved by integrating two units of green-emissive devices in series. The architecture of the device used in the experiment is Indium-Tin-Oxid (ITO)/CuPc/NPB/C545T:Alq(3)/Alq(3)/Mg:Alq(3)/WO3/NPB/C545T:Alq(3)/Alq(3)/LiF/Al. We found the efficiency of the two-unit devices can be controllable by the thickness Of WO3. The two-unit devices with 1-nm-thick WO3 produces the luminance efficiency of 49.2 cd/A at 20 mA/cm(2), which is around four times that of the controlled single-unit device (ITO/CuPc/NPB/C545T:Alq(3)/Alq(3)/LiF/Al). Compared with reported research data, the "amplification effect" discovered in our device is a rather unexpected result. The external quantum efficiency of 12.6%, with near-saturated Commission Internationale d'Eclairage coordinates (CIEx = 0.27, CIEy = 0.68), is one of the best ever reported for a fluorescent dye-doped OLED. We also demonstrate that the electron injection layer of Mg:Alq(3) is a necessary component for the enhancement of EL efficiency. These results may prove to be an effective method to enhance the efficiency as well as the lifetime of current OLEDs.
Highly efficient top-emitting white organic electroluminescent devices
(2005-06-20)
Hsu, SF
;
Lee, CC
;
Hwang, SW
;
Chen, CH
;
應用化學系
We have developed highly efficient white top-emitting organic light-emitting devices with broad emission by modifying both the anode and cathode. To alleviate the undesirable microcavity effect and obtain "broad" white emission, a CFx-coated Ag anode and an index-matching layer (SnO2) capped on a thin Ca/Ag cathode with a maximum transparency of 80% were employed. A top-emitting broad white-light device, based on the dual-layer architecture of light blue and yellow emitters with one of the highest EL efficiencies of 22.2 cd/A (9.6 1m/W) at 20 mA/cm(2) and 7.3 V with Commission Internationale d'Eclairage coordinates of (x = 0.31, y = 0.47), has been demonstrated. (c) 2005 American Institute of Physics.
Highly efficient white organic electroluminescent devices based on tandem architecture
(2005-12-19)
Chang, CC
;
Chen, JF
;
Hwang, SW
;
Chen, CH
;
電子物理學系
Two types of tandem organic light-emitting diodes (OLEDs) with white-light emission have been developed by using Mg:Alq(3)/WO3 as the interconnecting layer. While the Commission Internationale d'Eclairage (CIE) coordinates of the tandem device with individual blue- and yellow-emitting OLEDs was sensitive to the viewing angle and the operating time, the tandem device connecting two white-emitting OLEDs was considerably less. At an optimal WO3 thickness of 5 nm, the tandem two-unit device produced three higher luminance efficiency than that expected of a single-unit device. A maximum efficiency of 22 cd/A was achieved by the tandem device comprised of two white-fluorescent OLEDs, and the projected half-life under the initial luminance of 100 cd/m(2) was over 80 000 h.
Improved performance and stability of organic light-emitting devices with Al-Cu alloy cathode
(2005-02-28)
Chen, IC
;
Hwang, SW
;
Chen, CH
;
應用化學系
;
友訊交大聯合研發中心
We have developed a stable green organic electroluminescent (EL) device by using an Al-Cu alloy as a cathode, which has better performance and reliability than the device with an Al cathode. The device with an Al-Cu alloy cathode achieved an EL efficiency of 3.78 cd/A(2.18 lm/W) at 20 mA/cm(2) and the operating voltage was 5.46 V, while device with Al cathode had an EL efficiency of 3.1 cd/A(1.34 lm/W) and 7.3 V at the same drive condition. The Al-Cu device achieved a 20% decay lifetime (t(80)) of 1234 h at an initial brightness of 756 cd/m(2), which is twice the lifetime of conventional device with the state-of-the-art LiF/Al cathode. (C) 2005 American Institute of Physics.