Browsing by Author "Shih, Ping-I"

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A novel fluorene-triphenylamine hybrid that is a highly efficient host material for blue-, green-, and red-light-emitting electrophosphorescent devices
(2007-11-23)
Shih, Ping-I
;
Chien, Chen-Han
;
Wu, Tang-Iy
;
Shu, Ching-Fong
;
應用化學系
TFTPA (tris[4-(9-phenylfluoren-9-yl)phenyl]amine), a novel host material that contains a triphenylamine core and three 9-phenyl-9-fluorenyl peripheries, was effectively synthesized through a Friedel-Crafts-type substitution reaction. Owing to the presence of its sterically bulky 9-phenyl-9-fluorenyl groups, TFTPA exhibits a high glass transition temperature (186 degrees C) and is morphologically and electrochemically stable. In addition, as demonstrated from atomic force microscopy measurements, the aggregation of the triplet iridium dopant is significantly diminished in the TFTPA host, resulting in a highly efficient full-color phosphorescence. The performance of TFTPA-based devices is far superior to those of the corresponding mCP- or CBP-based devices, particularly in blue- and red-emitting electrophosphorescent device systems. The efficiency of the FIrpic-based blue-emitting device reached 12% (26 cd A(-1)) and 18 lm W-1 at a practical brightness of 100 cd m(-2); the Ir(piq)(2)acac-based red-emitting device exhibited an extremely low turn-on voltage (2.6 V) and a threefold enhancement in device efficiency (9.0 lm W-1) relative to those of reference devices based on the CBP host material.
Bright-white light-emitting devices based on a single polymer exhibiting simultaneous blue, green, and red emissions
(2007-01-23)
Chuang, Chu-Ying
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Shih, Ping-I
;
Chien, Chen-Han
;
Wu, Fang-Iy
;
Shu, Ching-Fong
We have developed efficient white-light-emitting polymers through the incorporation of low band gap green-light-emitting benzothiadiazole and red-light-emitting bisthiophenylbenzothiadiazole moieties into the backbone of a blue-light-emitting bipolar polyfluorene copolymer. Partial energy transfer from the blue-fluorescent polyfluorene backbone to the green- and red-fluorescent components resulted in individual emissions from the three emissive species. By carefully controlling the concentrations of the low-energy-emitting species in the resulting copolymers, the emission of white light, with contributions from each of the three primary colors, was achieved. Efficient polymer light-emitting devices prepared using these copolymers exhibited luminance efficiencies as high as 4.87 cd/A with color coordinates (0.37, 0.36) that were very close to the ideal CIE chromaticity coordinates for pure white light (0.33, 0.33). In addition, the color coordinates remained almost unchanged over a range of operating potentials. A mechanistic study suggested that energy transfer from the fluorene segments to the low band gap units, rather than charge trapping, was the main operating process involved in the electroluminescent process.
Carbazole-Based Ladder-Type Heptacylic Arene with Aliphatic Side Chains Leading to Enhanced Efficiency of Organic Photovoltaics
(2011-05-10)
Cheng, Yen-Ju
;
Wu, Jhong-Sian
;
Shih, Ping-I
;
Chang, Chih-Yu
;
Jwo, Pei-Chi
By utilizing Friedel-Crafts cyclization, we have successfully designed and synthesized a ladder-type heptacyclic carbazole-dicyclopentathiophene (CDCT-C8) unit in which two outer thiophene subunits are covalently fastened to the central 2,7-carbazole core. The nitrogen-directing effect of the carbazole unit facilitates the intrarnolecular cydization and thereby suppresses the acid-induced dehydration, allowing us to incorporate two octyl side chains on the cyclopentadiene rings in good chemical yield. The distannyl-CDCT-C8 building block was copolymerized with benzothiadiazole (BT), dithienylbenzothiadiazole (DTBT), dithienyldiketopyrrolopyrrole (DTDPP) and quinoxaline (QX) units by Stile polymerization to afford four alternating donor acceptor copolymers, PCDCTBT-C8, PCDCTDTBT-C8, PCDCTDTDPP-C8 and PCDCTQX-C8, respectively. The device based on the PCDCTBT-C8:PG7IBM (1:3 in wt%) blend exhibited a V(oc) of 0.74 V, a J(sc) of 10.3 mA/cm(2), a FF of 60%, delivering an impressive PCE of 4.6%. This value represents one of the best performances among carbazole-based conjugated polymers in the literatures. The corresponding PCDCTBT-C8 :PC(71)BM blend showed a high hole mobility of 1.2 x 10(-3) cm(2) V(-1) s(-1), which is in good agreement with its high current density and fill factor. This improved performance is associated with the modification of the aliphatic side chains on the CDCT structure to optimize the interchain interactions for enhanced charge transporting. The devices based on PCDCTDTBT-C8, PCDCTDTDPP-C8 and PCDCTQX-C8 polymers also displayed promising efficiencies of 3.5%, 2.4%, and 1.8%, respectively.
Efficient and robust charge-transporting polymers for highly efficient polymer light-emitting diodes
(2009-03-22)
Huang, Fei
;
Cheng, Yen-Ju
;
Liu, Michelle S.
;
Shih, Ping-I
;
Shu, Chingfong
Efficient non-doped blue-light-emitting diodes incorporating an anthracene derivative end-capped with fluorene groups
(2009)
Wu, Chen-Hao
;
Chien, Chen-Han
;
Hsu, Fang-Ming
;
Shih, Ping-I
;
Shu, Ching-Fong
We have synthesized and characterized a novel blue-emitting material, 2-tert-butyl-9,10-bis[40-(9-ptolylfluoren- 9-yl) biphenyl-4-yl] anthracene (BFAn), containing an anthracene core end-capped with 9-phenyl-9-fluorenyl groups. The presence of the sterically congested fluorene groups imparts BFAn with a high thermal decomposition temperature (T(d) = 510 degrees C) and results in its forming a stable glass (T(g) = 227 degrees C). Atomic force microscopy measurements revealed that BFAn forms high-quality amorphous films and possesses good morphological stability after annealing. Organic light-emitting diodes (OLEDs) featuring BFAn as the emitter exhibited an excellent external quantum efficiency of 5.1% (5.6 cd A(-1)) with Commission Internationale de L'Eclairage coordinates of (0.15, 0.12) that are very close to the National Television Standards Committee's blue standard. The power efficiency of our BFAn-based devices reached as high as 5.7 lmW(-1), making them superior to other reported non-doped deep-blue OLEDs.
Efficient white-light-emitting diodes based on poly(N-vinylcarbazole) doped with blue fluorescent and orange phosphorescent materials
(2006-06-19)
Shih, Ping-I
;
Shu, Ching-Fong
;
Tung, Yung-Liang
;
Chi, Yun
;
應用化學系
We have fabricated polymer white-light-emitting devices possessing a single emitting layer containing a hole-transporting host polymer, poly(N-vinylcarbazole), and an electron-transporting auxiliary, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, doped with a blue-light-emitting amino-substituted distyrylarylene fluorescent dye and an orange-light-emitting osmium phosphor. The doubly doped device exhibited an intense white emission having Commission Internationale de l'Eclairage coordinates of (0.33, 0.34), a high external quantum efficiency of 6.12% (13.2 cd/A), and a maximum brightness of 11 306 cd/m(2). The color coordinates remained unchanged over a range of operating voltages, even at luminance as high as 1x10(4) cd/m(2). (c) 2006 American Institute of Physics.
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
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Shih, Hung-Min
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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.
Highly efficient non-doped blue-light-emitting diodes based on an anthrancene derivative end-capped with tetraphenylethylene groups
(2007-11-05)
Shih, Ping-I
;
Chuang, Chu-Ying
;
Chien, Chen-Han
;
Diau, Eric Wei-Guang
;
Shu, Ching-Fong
A novel blue-emitting material, 2-tert-butyl-9,10-bis[4-(1,2,2-triphenylvinyl)phenyl]anthracene (TPVAn), which contains an anthracene core and two tetraphenylethylene end-capped groups, has been synthesized and characterized. Owing to the presence of its sterically congested terminal groups, TPVAn possesses a high glass transition temperature (155 degrees C) and is morphologically stable. Organic light-emitting diodes (OLEDs) utilizing TPVAn as the emitter exhibit bright saturated-blue emissions (Commission Internationale de L'Eclairage (CIE) chromaticity coordinates of x = 0.14 and y = 0.12) with efficiencies as high as 5.3% (5.3 cd A(-1)) - the best performance of non-doped deep blue-emitting OLEDs reported to date. In addition, TPVAn doped with an orange fluorophore served as an authentic host for the construction of a white-light-emitting device that displayed promising electroluminescent characteristics: the maximum external quantum efficiency reached 4.9% (13.1 cd A(-1)) with CIE coordinates located at (0.33, 0.39).
Highly Efficient Polymer White-Light-Emitting Diodes Based on Lithium Salts Doped Electron Transporting Layer
(2009-01-19)
Huang, Fei
;
Shih, Ping-I
;
Shu, Ching-Fong
;
Chi, Yun
;
Jen, Alex K. -Y.
A Li(2)CO(3)-doped water/alcohol-soluble neutral conjugated polymer is used as the electron-injection layer in a solution-processed polymer OWLED with very high efficiency. A maximum forward viewing luminous efficiency of 36.1 cd A(-1) and a power efficiency of 23.4 lm W(-1) were achieved, values comparable to those reported I-or the state-of-the-art vacuum deposited small-molecule OWLEDs.
Highly efficient red organic light-emitting devices based on a fluorene-triphenylamine host doped with an Os(II) phosphor
(2008-06-09)
Wu, Chen-Hao
;
Shih, Ping-I
;
Shu, Ching-Fong
;
Chi, Yun
;
應用化學系
We report highly efficient red-light-emitting devices based on a fluorene-triphenylamine tris[4-(9-phenylfluoren-9-yl)phenyl]amine (TFTPA) host doped with an osmium phosphor. The sterically hindered fluorene peripheries provided a compatible environment for the osmium dopant and alleviated concentration quenching of the phosphor at high doping levels. Increasing the doping concentration from 7 to 21 wt % dramatically decreased the driving voltage of the TFTPA-based devices, leading to improved power efficiency. The 21 wt % Os-doped device exhibited maximum luminous and powder efficiencies of 29.9 cd/A and 25.2 lm/W, combined with high efficiencies at high brightness. At 1000 cd/m(2) the efficiencies remained 29.2 cd/A and 22.2 lm/W. (C) 2008 American Institute of Physics.
Highly efficient white-electrophosphorescent devices based on polyfluorene copolymers containing charge-transporting pendent units
(2007)
Wu, Fang-Iy
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Shih, Ping-I
;
Tseng, Ya-Hsien
;
Shu, Ching-Fong
;
Tung, Yung-Liang
We have developed an efficient green-emitting polymer (FTO-BT5) through the incorporation of low-bandgap 2,1,3-benzothiadiazole (BT) moieties into the backbone of a blue-light-emitting polyfluorene copolymer (PF-TPA-OXD), which contains hole-transporting triphenylamine (TPA) and electron-transporting oxadiazole (OXD) pendent groups. A polymer light-emitting device based on this BT-containing copolymer exhibited very bright green emission having Commission Internationale d'E'nclairage (CIE) chromaticity coordinates (0.32, 0.61); the maximum brightness was 10232 cd m(-2) and the maximum luminance efficiency was 8.9 cd A(-1). In addition, a highly efficient three-band white-light-emitting diode was prepared using PF-TPA-OXD as a blue-light-emitting host doped with this green-light-emitting FTO-BT5 copolymer and a red-light-emitting Os phosphor Os(fppz). Without co-doping any other electron-and/or hole-transporting molecules, this white-light-emitting device reached a maximum external quantum efficiency of 4.1% (8.3 cd A(-1)) at a luminance of 402 cd m(-2) and a current density of 4.8 mA cm(-2). When the luminance increased from 26 cd m(-2) (0.36, 0.32) to 5258 cd m(-2) (0.33, 0.31), the corresponding CIE chromaticity coordinates remain almost unaltered and very close to the emission of pure white light; the value of eta(ext) remained above 3% in this high-luminance region.
Interface Engineering to Enhance the Efficiency of Conventional Polymer Solar Cells by Alcohol-/Water-Soluble C-60 Materials Doped with Alkali Carbonates
(2013-06-12)
Lai, Yu-Ying
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Shih, Ping-I
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Li, Yi-Peng
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Tsai, Che-En
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Wu, Jhong-Sian
Two new C-60-based n-type materials, EGMC-OH and EGMC-COOH, functionalized with hydrophilic triethylene glycol groups (TEGs), have been synthesized and employed in conventional polymer solar cells. With the assistance of the TEG-based surfactant, EGMC-OH and EGMC COOH can be dissolved in highly polar solvents to implement the polar/nonpolar orthogonal solvent strategy, forming an electron modification layer (EML) without eroding the basis of ITO/PEDOT:PSS/P3HT:PC61M/EML/Ca/Al configuration with the insertion of the EGMC OH and EGMC COOH EML between the active layer and the electrode have thus been successfully realized by cost-effective solution processing techniques. Moreover, the electron conductivity of the EML can be improved by incorporating alkali carbonates into the EGMC-COOH EML. Compared to the pristine device with a PCE of 3.61%, the devices modified by the Li2CO3-doped EGMC-COOH EML achieved a highest PCE of 4.29%. Furthermore, we demonstrated that the formation of the EGMC-COOH EML can be utilized as a general approach in the fabrication of highly efficient multilayer conventional devices. With the incorporation of the EGMC-COOH doped with 40 wt % Li2CO3, the PCDCTBT-C8:PC17BM-based device exhibited a superior PCE of 4.51%, which outperformed the corresponding nonmodified device with a PCE of 3.63%.
Lithium salt doped conjugated polymers as electron transporting materials for highly efficient blue polymer light-emitting diodes
(2008-12-15)
Huang, Fei
;
Shih, Ping-I
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Liu, Michelle S.
;
Shu, Ching-Fong
;
Jen, Alex K. -Y.
Highly efficient blue polymer light-emitting diodes (PLEDs) are fabricated using a conjugated polymer, poly[9,9-bis(2-(2-(2-diethanol-amino-ethoxy) ethoxy) ethyl) fluorene-alt-4, 4(')-phenylether] as an electron transporting layer (ETL). It was found that the performance of these blue-emitting devices could be greatly improved if the ETL was doped with LiF or Li(2)CO(3) salts. A bis[(4,6-di-fluorophenyl)-pyridinato-N, C(2)] (picolinate) Ir(III) (FIrpic) complex based blue phosphorescent PLED exhibited a maximum luminance efficiency of 20.3 cd/A with a luminance of 1600 cd/m(2) at the current density of 7.9 mA/cm(2) and drive voltage of 8.0 V.
Novel carbazole/fluorene hybrids: Host materials for blue phosphorescent OLEDs
(2006-06-22)
Shih, Ping-I
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Chiang, Chih-Long
;
Dixit, Ajay Kumar
;
Chen, Ching-Kun
;
Yuan, Mao-Chuan
A series of carbazole/fluorene (CBZm-Fn) hybrids were effectively synthesized through Friedel-Crafts-type substitution of the carbazole rings. These compounds were thermally and morphologically stable host materials for OLED applications. Efficient blue phosphorescent OLEDs were obtained when employing CBZ1-F2 as the host and Firpic as the guest.
Novel host material for highly efficient blue phosphorescent OLEDs
(2007)
Shih, Ping-I
;
Chien, Chen-Han
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Chuang, Chu-Ying
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Shu, Ching-Fong
;
Yang, Cheng-Han
We report the synthesis and characterization of a novel silane - fluorene hybrid, triphenyl-(4-(9-phenyl- 9H-fluoren-9-yl) phenyl) silane (TPSi-F), used as the host material for blue phosphorescent devices. TPSi-F is constructed by linking p-substituted tetraphenylsilane to the fluorene framework through a non-conjugated, sp(3)-hybridized carbon atom (C- 9) to enhance thermal and morphological stabilities, while maintaining the much needed higher singlet and triplet energy gap. Highly efficient sky-blue phosphorescent OLEDs were obtained when employing TPSi-F as the host and iridium(III) bis[(4,6-difluorophenyl) pyridinato-N,C-2'] (FIrpic) as the guest. The maximum external quantum efficiency (max. E. Q. E.) of this device reached as high as 15% (30.6 cd A(-1)). Furthermore, upon switching the guest from FIrpic to a new blue phosphor FIrfpy, better blue-emitting OLEDs were produced with a max. E. Q. E. of 9.4% (15.1 cd A(-1)). These TPSi-F based blue phosphorescent devices show a 2-fold enhancement in device efficiency compared with reference devices based on the conventional host material 1,3-bis(9-carbazolyl) benzene (mCP).
Phosphine-Oxide-Containing Bipolar Host Material for Blue Electrophosphorescent Devices
(1970-01-01)
Hsu, Fang-Ming
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Chien, Chen-Han
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Shih, Ping-I
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Shu, Ching-Fong
;
應用化學系
"We report highly efficient blue electrophosphorescent organic light-emitting diodes (OLEDs) incorporating a bipolar host, 2,7-bis(diphenylphosphine oxide)-9-(9-phenylcarbazol-3-yl)-9-phenylfluorene (PCF), doped with iridium(III) bis[(4,6-difluorophenyl)pyridinato-NC2']picolinate (FIrpic). PCF, which contains diphenylphosphine oxide groups appended onto a carbazole/fluorene hybrid, displays both electron- and hole-tran sporting characteristics, resulting in a low turn-on voltage (2.6 V) and greatly improved power efficiencies. In addition, the sterically hindered structure of PCF provides a compatible environment for the FIrpic dopant, alleviating concentration quenching of the phosphor at high doping levels. The device doped with 28 wt % FIrpic exhibited maximum EL efficiencies of 30.8 cd/A and 26.2 lm/W (at 121 cd/m(2)) /m(2), Even at a high brightness of 1000 cd/m(2) the efficiencies remained high (26.9 cd/A and 19.6 lm/W)."
Polyfluorene presenting dipolar pendent groups and its application to electroluminescent devices
(2007-06-01)
Chien, Chen-Han
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Shih, Ping-I
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Wu, Fang-Iy
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Shu, Ching-Fong
;
Chi, Yun
We have synthesized a blue-light-emitting polyfluorene derivative (PF-TPAOXD) that presents sterically hindered, dipolar pendent groups functionalized at the C-9 positions of alternating fluorene units. The incorporation of the dipolar side chains, each comprising an electron-rich triphenylamine group and an electron-deficient oxadiazole group connected through a pi-conjugated bridge, endows the resultant polymer with higher highest occupied molecular orbital and lower lowest unoccupied molecular orbital energy levels, which, consequently, lead to an increase in both hole and electron affinities. An electroluminescent device incorporating this polymer as the emitting layer exhibited a stable blue emission with a maximum brightness of 2080 cd/ m(2) at 12 V and a maximum external quantum efficiency of 1.4% at a brightness of 137 cd/m(2). Furthermore, atomic force microscopy measurements indicated that the dipolar nature of PF-TPAOXD, in contrast to the general nonpolarity of polydialkylfluorenes, provided a stabilizing environment allowing the polar organometallic triplet dopant to be dispersed homogeneously. We also fabricated an electrophosphorescent device incorporating PF-TPAOXD as the host material doped with a red-emitting osmium complex to realize red electroluminescence with Commission Internationale de l'Eclairage color coordinates of (0.66, 0.34). The resulting device exhibited a maximum external quantum efficiency of 7.3% at a brightness of 1747 cd/m(2) and a maximum brightness of 7244 cd/ m(2). (C) 2007 Wiley Periodicals, Inc.
Polymers derived from 3,6-fluorene and tetraphenylsilane derivatives: Solution-processable host materials for green phosphorescent OLEDs
(2008-06-10)
Yeh, Huan-Chi
;
Chien, Chen-Han
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Shih, Ping-I
;
Yuan, Mao-Chuan
;
Shu, Ching-Fong
We have synthesized two fluorene-based polymeric host materials, P1 and P2, through palladium-catalyzed Suzuki couplings of monomers containing tetraphenylsilane and 3,6-disubstituted fluorene frameworks, respectively. The resultant copolymers exhibited high glass transition temperatures (T-g >= 215 degrees C) and excellent thermal stability. The conjugation lengths of polymers P1 and P2 were effectively confined through the presence of the 3,6-linkages and silane units in the polymer skeleton. The structural features endowed these copolymers with UV-violet emissions in the solid state, together with high triplet energies (E-T = 2.60 eV), which were sufficiently high for PI and P2 to serve as appropriate hosts for green-emitting phosphors. In the case of polymer P2, the incorporation of pendent carbazole groups increased the HOMO level markedly and balanced the rates of charge injection and transportation. Employing P2 doped with green-emitting fac-tris(2-phenylpyridine)iridium as the emissive layer, we fabricated highly efficient polymer light-emitting diodes (32 cd/A, 9.2%) that exhibited significantly enhanced EL performance relative to that of the system employing P1 (14.5 cd/A, 4.2%).
Pt(II) Complexes with 6-(5-Trifluoromethyl-Pyrazol-3-yl)-2,2 '-Bipyridine Terdentate Chelating Ligands: Synthesis, Characterization, and Luminescent Properties
(2008-01-01)
Chen, Jing-Lin
;
Chang, Sheng-Yuan
;
Chi, Yun
;
Chen, Kellen
;
Cheng, Yi-Ming
A series of Pt(II) complexes Pt(fpbpy)Cl (1), Pt(fpbpy)(OAc) (2), Pt(fpbpy)(NHCOMe) (3), Pt(fpbpy)(NHCOEt) (4), and [Pt(fpbpy)(NCMe)](BF(4)) (5) with deprotonated 6-(5-trifluoromethyl-pyrazol-3-yl)-2,2'-bipyridine terdentate ligand are prepared, among which 1 is converted to complexes 2-5 by a simple ligand substitution. Alternatively, acetamide complex 3 is prepared by hydrolysis of acetonitrile complex 5, while the back conversion from 3 to 1 is regulated by the addition of HCl solution, showing the reaction sequence 1 -> 5 -> 3 -> 1. Mullilayer OLED devices are successfully fabricated by using triphenyl-(4-(9-phenyl-9H-fluoren-9-yl)phenyl) silane (TPSi-F) as host material and with doping concentrations of 1 varying from 7 to 100%. The electroluminescence showed a substantial red-shifting versus the normal photoluminescence detected in solution. Moreover, at a doping concentration of 28%, the device showed a saturated red luminescence with a maximum external quantum yield of 8.5% at 20 mA cm(-2) and a peak luminescence of 47543 cd m(-2) at 18.5 V.
Pt-II Complexes with 6-(5-Trifluoromethyl-Pyrazol-3-yl)-2,2 '-Bipyridine Terdentate Chelating Ligands: Synthesis, Characterization, and Luminescent Properties
(2008-01-01)
Chen, Jing-Lin
;
Chang, Sheng-Yuan
;
Chi, Yun
;
Chen, Kellen
;
Cheng, Yi-Ming
A series of Pt-II complexes Pt(fpbpy)Cl (1), Pt(fpbpy)(OAc) (2), Pt(fpbpy)(NHCOMe) (3), Pt(fpbpy)(NHCOEt) (4), and [Pt(fpbpy)(NCMe)](BF4) (5) with deprotonated 6-(5-trifluoromethyl-pyrazol-3-yl)-2,2'-bipyridine terdentate ligand are prepared, among which 1 is converted to complexes 2-5 by a simple ligand substitution. Alternatively, acetamide complex 3 is prepared by hydrolysis of acetonitrile complex 5, while the back conversion from 3 to 1 is regulated by the addition of HCl solution, showing the reaction sequence 1 -> 5 -> 3 -> 1. Mullilayer OLED devices are successfully fabricated by using triphenyl-(4-(9-phenyl-9H-fluoren-9-yl)phenyl) silane (TPSi-F) as host material and with doping concentrations of 1 varying from 7 to 100%. The electroluminescence showed a substantial red-shifting versus the normal photoluminescence detected in solution. Moreover, at a doping concentration of 28%, the device showed a saturated red luminescence with a maximum external quantum yield of 8.5% at 20 mA cm(-2) and a peak luminescence of 47543 cd m(-2) at 18.5 V.