Browsing by Author "Shih, Hung-Min"

Now showing 1 - 4 of 4

Exciplex Electroluminescence Induced by Cross-Linked Hole-Transporting Materials for White Light Polymer Light-Emitting Diodes
(2011-08-09)
Cheng, Yen-Ju
;
Liao, Ming-Hung
;
Shih, Hung-Min
;
Shih, Ping-I
;
Hsu, Chain-Shu
A new class of cross-linkable N,N,N,N'-tetrapheny1-1,1'-biphenyl-4,4'-diame (TPD)-based hole-transporting materials (HTMs), DV-OMe-TPD, DV-Me-TPD, and DV-F-TPD, were designed and synthesized. Two vinyl groups in the TPD units are used for thermal cross-linking, whereas methoxy, methyl and fluoro groups are introduced to modulate the HOMO energy levels of the HTMs. These HTMs are thermally cross-linked to overcome interfacial mixing, realizing solution-processed polyfluorene (PFO)-based devices (ITO/cross-linked HTMs/PFO/CsF/ Al). Besides the characteristic blue emission of PFO, the devices exhibited a red emission whose energy is highly dependent on the HOMO energy of the cross-linked HTM used in the device. This result suggests that the red electroluminescence is derived from the exciplex generated by the adjacent hole and electron at the cross-linked HTM/fluorenone heterojunction interface. By doping small amount of 4,7-bis(9,9-dihexylfluoren-2-yl)-2,1,3-benzothiadiazole (BFBT) into the emissive layer (EML) to compensate green emission, the devices with the configuration of ITO/PEDOT:PSS/DV-Me-TPD/PFO doped with BEBT/CsF/Al exhibited white electroluminescence comprising three primary colors simultaneously. The 0.04 wt % doped device achieved a maximum luminous efficiency of 5.28 cd/A, which represents the highest efficiency for WPLEDs reported so far on the basis of the exciplex strategy. This device showed CIE chromaticity coordinates of (0.82, 0.42) which are close to the ideal white point (0.33, 0.33). We have demonstrated that integrating cross-linked triarylamine-based HTMs with fluorenone defects in PFO to induce exciplex electroluminescence can provide a useful way for realizing WPLED devices.
High-performance poly(2,3-diphenyl-1,4-phenylene vinylene)-based polymer light-emitting diodes by blade coating method
(2011-08-03)
Liao, Yung-Ming
;
Shih, Hung-Min
;
Hsu, Kuang-Hui
;
Hsu, Chain-Shu
;
Chao, Yu-Chiang
A new series of super high brightness and luminance efficient poly(2,3-diphenyl-1,4-phenylene vinylene) (DP-PPV)-based electroluminescent (EL) polymers containing methoxy or long branched alkoxy chains were synthesized via Gilch polymerization. The branched alkoxy groups were introduced to enhance solubility for blade and spin-coating processes. Monomers of DMeO-PPV and m-Ph-PPV were used to increase steric hindrance and prevent close packing of the main chain. By controlling the feeding ratio of different monomers during polymerization, DP-PPV derivatives with high molecular weight were obtained. All synthesized polymers possess high glass transition temperatures and thermal stabilities. The maximum photoluminescent emissions of the thin films are located between 544 and 547 nm. Cyclic voltammetry analysis reveals that the band gaps of these light-emitting materials are in the range of 2.75 -2.84 eV. Blade coating was used to fabricate multilayer polymer light-emitting diodes. A multilayer electroluminescent device with the configuration of ITO/PEDOT:PSS/TFB/P1/TPBi/LiF/Al exhibited a very high luminescence efficiency (10.96 cd A(-1)). The maximum brightness of the multilayer EL device ITO/PEDOT:PSS/TFB/P3/CsF/Al reached up to 78,050 cd m(-2) with a low turn-on voltage (4.0 V). For further investigation, polymer P3 was blended with DPPFBNA to achieve white light-emitting device; the multilayer devices generated a maximum brightness of 1085 cd m(-2) and a luminance efficiency of 0.75 cd A(-1), with CIE coordinates (0.28, 0.33) at 11 V. (C) 2011 Elsevier Ltd. All rights reserved.
Synthesis of fluorene-based hyperbranched polymers for solution-processable blue, green, red, and white light-emitting devices
(2012-02-15)
Shih, Hung-Min
;
Wu, Ren-Chi
;
Shih, Ping-I
;
Wang, Chien-Lung
;
Hsu, Chain-Shu
For the purpose of making hyperbranched polymer (Hb-Ps)-based red, green, blue, and white polymer light-emitting diodes (PLEDs), three Hb-Ps Hb-terfluorene (Hb-TF), Hb-4,7-bis(9,9'-dioctylfluoren-2-yl)-2,1,3-benzothiodiazole (Hb-BFBT), and Hb-4,7-bis[(9,9'-dioctylfluoren-2-yl)-thien-2-yl]-2,1,3-benzothiodiazole (Hb-BFTBT) were synthesized via [2+2+2] polycyclotrimerization of the corresponding diacetylene-functionalized monomers. All the synthesized polymers showed excellent thermal stability with degradation temperature higher than 355 degrees C and glass transition temperatures higher than 50 degrees C. Photoluminance (PL) and electroluminance (EL) spectra of the polymers indicate that Hb-TF, Hb-BFBT, and Hb-BFTBT are blue-green, green, and red emitting materials. Maximum brightness of the double-layer devices of Hb-TF, Hb-BFBT, and Hb-BFTBT with the device configuration of indium tin oxide/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)/light-emitting polymer/CsF/Al are 48, 42, and 29 cd/m(2); the maximum luminance efficiency of the devices are 0.01, 0.02, and 0.01 cd/A. By using hostguest doped system, saturated red electrophosphorescent devices with a maximum luminance efficiency of 1.61 cd/A were obtained when Hb-TF was used as a host material doped with Os(fptz)(2)(PPh(2)Me(2))(2) as a guest material. A maximum luminance efficiency of 3.39 cd/A of a red polymer light-emitting device was also reached when Hb-BFTBT was used as the guest in the PFO (Poly(9,9-dioctylfluorene)) host layer. In addition, a series of efficient white devices were, which show low turn-on voltage (3.5 V) with highest luminance efficiency of 4.98 cd/A, maximum brightness of 1185 cd/m(2), and the Commission Internationale de l'Eclairage (CIE) coordinates close to ideal white emission (0.33, 0.33), were prepared by using BFBT as auxiliary dopant. (c) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 696-710, 2012
Synthesis of New Blue Anthracene-based Conjugated Polymers and Their Applications in Polymer Light-Emitting Diodes
(2011-06-01)
Shih, Hung-Min
;
Lin, Cheng-Jui
;
Tseng, Shin-Rong
;
Lin, Chih-Hung
;
Hsu, Chain-Shu
A series of anthracene-based conjugated copolymers containing 9,10-bis(6-bromonaphthalen-2- yl)-2-tert-butylanthracene (BNA) and 2,7-diphenyl substituted fluorene (DPPF) moieties are prepared via a palladium-catalyzed Suzuki polymerization. All of the synthesized polymers emit blue light at around 450nm and show good thermal and color stability. Their electro-luminescence spectra remain unchanged at high driving voltage. The double-layer polymer light-emitting diode (PLED) fabricated with ITO/PEDOT: PSS/DPPFBNA3/CsF/Al, produces a maximum brightness of 1 650 cd.m(-2) and has a luminance efficiency of 0.39 cd.A(-1). The ITO/PEDOT: PSS/TFB/DPPFBNA3/CsF/Al multilayer PLED, incorporating a TFB layer to facilitate hole transportation, produces a maximum brightness of 5 371 cd.m(-2) and a luminance efficiency of 1.18 cd.A(-1)