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1.
Organic light-emitting device (OLED) was fabricated using the novel red phosphorescent heteroleptic tris-cyclometalated iridium complex, bis(2-phenylpyridine)iridium(III)[2(5′-methylphenyl)-4-diphenylquinoline] [Ir(ppy)2(dpq-5CH3)], based on 2-phenylpyridine (ppy) and 2(5′-methylphenyl)-4-diphenylquinoline (dpq-5CH3) ligand. Generally, the ppy ligand in heteroleptic iridium complexes plays an important role as “sensitizer” in the efficient energy transfer from the host (CBP; 4,4,N,N′-dicarbazolebiphenyl) to the luminescent ligand (dpq-5CH3). We demonstrated that high efficiency through the “sensitizer” can be obtained, when the T1 of the emitting ligand is close to T1 of the sensitizing ligand. The device containing Ir(ppy)2(dpq-5CH3) produced red light emission of 614 nm with maximum luminescence efficiency and power efficiency of 8.29 cd/A (at 0.09 mA/cm2) and 5.79 lm/W (at 0.09 mA/cm2), respectively. 相似文献
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We report single dopant single emissive layer white organic electroluminescent (EL) device based on the heteroleptic tris-cyclometalated iridium(III) complex, Ir(dfppy)2(pq), as the guest, where dfppy and pq are 2-(2,4-difluorophenyl) pyridine and 2-phenylquinoline, respectively, and 1,4-phenylenesis(triphenylsilane) (UGH2) as the host. The maximum luminous and power efficiencies of the device were 11.00 cd/A (J = 0.05 mA/cm2) and 5.60 lm/W (J = 0.001 mA/cm2), respectively. The CIE coordinates of the device with Ir(dfppy)2(pq) are (0.443, 0.473) and the EL spectrum of device shows emission band at 473 and 544 nm, at the applied voltage of 12 V. The similar phosphorescent decay rate of two ligands can lead to emit luminescence in two ligands at the same time. 相似文献
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We demonstrated efficient white electrophosphorescence with a heavily doped phosphorescent blue emitter and a triplet exciton blocking layer (TEBL) inserted between the hole transporting layer (HTL) and the emitting layer (EML). We fabricated white organic light-emitting diodes (WOLEDs) (devices A, B, C, and D) using a phosphorescent red emitter; bis(2-phenylquinolinato)-acetylacetonate iridium III (Ir(pq)2acac) doped in the host material; N,N′-dicarbazolyl-3,5-benzene (mCP) as the red EML and the phosphorescent blue emitter; bis(3,5-Difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl) iridium III (FIrpic) doped in the host material; p-bis(triphenylsilyly)benzene (UGH2) as the blue EML. The properties of device B, which demonstrate a maximum luminous efficiency and external quantum efficiency of 26.83 cd/A and 14.0%, respectively, were found to be superior to the other WOLED devices. It also showed white emission with CIEx,y coordinates of (x = 0.35, y = 0.35) at 8 V. Device D, which has a layer of P-type 4,4′,4″-tri(N-carbazolyl)triphenylamine (TCTA) material between the HTL and TEBL, was compared with device A to determine the 430 nm emission peak. 相似文献
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Dielectric properties of organic light-emitting diodes were investigated using ITO/Alq3/Al device. In spite of various advantages in organic light-emitting diodes, a fundamental study on physical properties is not yet sufficient. Dielectric properties are used for studying fundamental physical properties of materials through a frequency-dependent response. We have investigated magnitude and phase of impedance, electrical conductivity, and the dielectric loss depending on a bias-voltage variation using ITO/Alq3(60 nm)/Al device. The device shows a frequency-dependent response such that a major contribution is resistive below time constant and capacitive above time constant. Also, the device shows a voltage-dependent electrical conductivity in low-frequency region. A bulk resistance rapidly decreases as the frequency increases above 1 MHz. The dielectric loss shows that there appears an interfacial polarization in low-frequency region, and an orientational polarization in high-frequency region. 相似文献
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The effects of buffer layers, including LiF, LiCl, NaF, NaCl, NaI, KI, RbF, RbCl, CsF, CsCl, MgF2, CaF2, BaF2, and BaCl2 on electron injection and device performance in organic light-emitting diodes based on tris-(8-hydroxyquinoline) aluminum, were investigated systematically. The insertion of the buffer layers at the organic/cathode interface not only reduced the operating voltage, but also enhanced the luminance and efficiency, which is attributed to the improvement of electron injection efficiency. It was found that the efficiency of the electron injection was closely related to the inherent properties of the buffer layer, such as its melting point (MP) and dielectric constant (ε), as well as with the buffer layer's interface with the metallic electrode through the effective work function (WF). Low MP, low ε and low WF values result in an effective improvement in the injection of the electrons, and thus to the device performance. The electroluminescent performance was further improved by the introduction of calcium between the buffer layer and the aluminum electrode. 相似文献
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Phosphorescent organic light-emitting diodes (PHOLEDs) with an emitting layer of 4,4′-N,N′-dicarbazole-biphenyl codoped with phosphor fac-tri(phenylpyridine)iridium(III) [Ir(ppy)3] and fluorophore N,N’-dimethy-quinacridone (DMQA) are investigated. Predominant emission from DMQA due to the efficient energy transfer from Ir(ppy)3 to DMQA is observed. Such an energy transfer results in the transition of Ir(ppy)3 triplet to DMQA singlet, which reduces the Ir(ppy)3 exciton lifetime and hence suppresses the triplet-triplet annihilation and triplet-polaron annihilation of Ir(ppy)3 excitons, leading to dramatical reduction of the efficiency roll-off of the PHOLEDs. This transition of triplet to singlet strategy provides a method to improve the efficiency roll-off of the PHOLEDs. 相似文献
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A series of red-phosphorescent iridium (III) complexes 1-4 based on 5-benzoyl-2-phenylpyridine derivatives was synthesized. Their photophysical and electrophosphorescent properties were investigated. Multilayered OLEDs were fabricated with a device structure ITO/4,4′,4″-tris(N-(naphtalen-2-yl)-N-phenyl-amino)triphenylamine (60 nm)/4,4′-bis(N-naphtylphenylamino)biphenyl (20 nm)/Ir(III) complexes (8%) doped in 4,4′-N,N′-dicarbazolebiphenyl (30 nm)/2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (10 nm)/tris(8-hydroxyquinolinyl)aluminum(III) (20 nm)/Liq (2 nm)/Al (100 nm). All devices exhibited efficient red emissions. Among those, in a device containing iridium complex 1 dopant, the maximum luminance was 14200 cd/m2 at 14.0 V. Also, its luminous, power, and quantum efficiency were 10.40 cd/A, 3.44 lm/W and 9.21% at 20 mA/cm2, respectively. The peak wavelength of the electroluminescence was 607 nm, with CIE coordinates of (0.615, 0.383) at 12.0 V, and the device also showed a stable color chromaticity with various voltages. 相似文献
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Kyoung Soo Yook 《Thin solid films》2010,518(15):4462-2496
High efficiency phosphorescent white organic light-emitting diodes (PHWOLEDs) were developed by using a spirofluorene based phosphine oxide (SPPO1) as a host material in blue emitting layer. A stack structure of red:green/blue with an interlayer was used and the device performances of PHWOLEDs were investigated according to host composition in red:green emitting layer and the interlayer thickness. The use of SPPO1 as a host in the blue emitting layer resulted in a high quantum efficiency of 13.5% and a current efficiency of 27.6 cd/A with a color coordinate of (0.37, 0.43). 相似文献
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Yong Hwan Park 《Thin solid films》2007,515(12):5084-5089
The synthesis and photophysical study of efficient phosphorescent heteroleptic tris-cyclometalated iridium(III) complexes having two different (C^N) ligands are reported. In order to improve the luminescence efficiency by avoiding triplet-triplet (T-T) annihilation, new heteroleptic tris-cyclometalated iridium complexes, Ir(ppy)2(dpq), Ir(ppy)2(dpq-3-F) and Ir(ppy)2(dpq-CF3), are designed and prepared where ppy, dpq, dpq-3-F and dpq-CF3 represent 2-phenylpyridine, 2,4-diphenylquinoline, 2-(3-fluorophenyl)-4-phenylquinoline, and 4-phenyl-2-(4-(trifluoromethyl)phenyl)quinoline, respectively. Ppy ligands and dpq derivatives can act as a source of energy supply. When new heteroleptic tris-cyclometalated iridium complex, Ir(ppy)2(dpq-3-F) is placed in the lowest excited state, the excitation energy is neither quenched nor deactivated but quickly intermolecularly transferred from two ppy ligands to one luminescent dpq-3-F ligand. Such transfer can occur because the triplet energy level of Ir(ppy)3 is higher than that of Ir(dpq-3-F)3 and because Ir(dpq-3-F)3 was known to have a shorter lifetime than that of Ir(ppy)3. As a result, Ir(ppy)2(dpq-3-F) shows strong emission band at 620 nm from dpq-3-F ligand in the end. Thus it allows more reddish luminescent color and improves the luminescence by the decrease of quenching or energy deactivation by decreasing the number of the luminescent ligand. To analyze luminescent mechanism, we calculated these complexes theoretically by using computational method. 相似文献
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Sang Eok Jang 《Thin solid films》2010,519(2):906-910
High efficiency simple blue phosphorescent organic light-emitting diodes (PHOLEDs) without any electron injection layer were developed using a spirobifluorene-based phosphine oxide (SPPO13) as a host material in the emitting layer. A high quantum efficiency of 20.3% was obtained from the SPPO13 device, with a common device structure and quantum efficiency of 19% achieved in the simple blue device without any LiF electron injection layer. Efficient electron injection from the Al cathode to the SPPO13, without any electron injection layer, was responsible for the high quantum efficiency in the blue PHOLEDs. 相似文献
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Two oligomers with X-shaped repeating units bearing anthracene and fluorene units were synthesized in a facile procedure, and exhibited high photoluminescence efficiencies, thermal stabilities and good solubility. Their ease of processing enabled spin coating with an electron-transporting bitriazine layer to afford organic light-emitting diodes which displayed a light blue emission with the maximum luminance of 3650 cd/m2 and the current efficiency of 0.69 cd/A at an operation voltage of 10 V. 相似文献
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Hyun Ju KangKum Hee Lee Seok Jae LeeJi Hyun Seo Young Kwan Kim Seung Soo Yoon 《Thin solid films》2011,519(19):6544-6549
A series of phosphorescent Ir(III) complexes 1-4 were synthesized based on aryl(6-arylpyridin-3-yl)methanone ligands, and their photophysical and electroluminescent properties were characterized. Multilayer devices with the configuration, Indium tin oxide/4,4′,4″-tris(N-(naphthalene-2-yl)-N-phenyl-amino)triphenylamine (60 nm)/4,4′-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (20 nm)/Ir(III) complexes doped in N,N′-dicarbazolyl-4,4′-biphenyl (30 nm, 8%)/2,9-dimethyl-4,7-diphenyl-phenathroline (10 nm)/tris(8-hydroxyquinoline)-aluminum (20 nm)/lithium quinolate (2 nm)/ Al (100 nm), were fabricated. Among these, the device employing complex 2 as a dopant exhibited efficient red emission with a maximum luminance, luminous efficiency, power efficiency and quantum efficiency of 16200 cd/m2 at 14.0 V, 12.20 cd/A at 20 mA/cm2, 4.26 lm/W and 9.26% at 20 mA/cm2, respectively, with Commission Internationale de l'Énclairage coordinates of (0.63, 0.37) at 12.0 V. 相似文献
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A high triplet energy phosphine oxide derivative as a host and exciton blocking material for blue phosphorescent organic light-emitting diodes 总被引:1,自引:0,他引:1
Soon Ok Jeon 《Thin solid films》2010,518(14):3716-3720
We have designed and synthesized a blue phosphorescent host material based on a phosphine oxide moiety. 2-(diphenylphosphine oxide)-9,9′-spirobifluorene (SPPO1) was compared with N,N′-dicarbazolyl-3,5-benzene (mCP) as a blue host material in blue phosphorescent organic light-emitting diodes (PHOLEDs). The SPPO1 was effective as a host for blue PHOLEDs and the SPPO1 based blue PHOLEDs showed much higher quantum efficiency than common mCP based blue PHOLEDs. A high quantum efficiency of 16.3% and a current efficiency of 31.4 cd/A were obtained in the blue PHOLED with iridium(III) bis(4,6-(di-fluorophenyl)-pyridinato-N,C2′) picolinate (FIrpic) as a blue phosphorescent dopant. In addition, SPPO1 was also effective as an exciton blocking material for the blue PHOLED. 相似文献
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以具有生物染色作用的中性红染料为主结构,设计合成了两个新型中性红衍生物2-(N-邻苯二甲酰亚胺)-3-甲基-8-二甲胺吩嗪(NRDl)和N,N'-二(3-甲基-8二甲胺-2-吩嗪)-1,4,5,8-萘二酰亚胺(NRD2).实验制作了结构为ITO/NPB(43 nm)/Alq3:dopant(20 nm)/Alq3(32 nm)/Lif(1 nm)/Al(120 nm)的发光器件,在掺杂质量百分比浓度分别为1.0%、2.3%和4.1%时,NRDl的发光峰值分别为582 nm、588 nm和594 nm,在电压为12 V时,发光亮度达到5552cd·m-2,2858 cd·m-2和1985 cd·m-2.在掺杂质量百分比浓度为1.0%时,NRD2的发光峰值为558 nm,在电压为12 V时,发光亮度达到938 cd·m-2. 相似文献
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Li L Yu Z Hu W Chang CH Chen Q Pei Q 《Advanced materials (Deerfield Beach, Fla.)》2011,23(46):5563-5567
Blue, green, and red electrophosphorescent polymer light-emitting diodes have been fabricated on silver nanowire-polymer composite electrode. The devices are 20%-50% more efficient than control devices on ITO/glass and exhibit small efficiency roll-off at high luminances. The blue PLEDs were repeatedly bent to 1.5 mm radius concave or convex with calculated strain in the emissive layer approximately 5% (tensile or compressive). 相似文献
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In this paper, energy relation between blue emissive layer (blue-EML) and red emissive layer (red-EML) in organic light-emitting diodes based on blue-emitting and red-emitting phosphorescent dopants, bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl) iridium III (Firpic) and bis(2-(2′-benzo[4,5-α]thienyl)pyridinato-N,C3′)iridium(acetylacetonate) (Btp2Ir(acac)), was studied. Two phosphorescent dopants, Firpic and Btp2Ir(acac), were co-doped in the single emissive layer, and the results exhibit complete energy transfer from Firpic to Btp2Ir(acac). Then, Firpic and Btp2Ir(acac) were doped into blue-EML and red-EML, separately. By inserting 4,4′-bis(N-carbazolyl)biphenyl (CBP) spacer between blue- and red-EML, energy relation between blue- and red-EML was researched. The results of this work reveal that, CBP spacer may strengthen energy transfer between blue- and red-EML. The reason is that CBP triplets at blue-/red-EML interface can transfer their energies to both CBP molecules of red-EML and Firpic molecules of blue-EML in spacer-without devices, while CBP triplets in the spacer can transfer their energies only to CBP molecules of red-EML. Therefore, energy flow from blue- to red-EML is strengthened because of the avoidance of energy transfer from CBP triplets in the spacer to Firpic molecules of blue-EML, leading to the relative enhancement of red emission in CBP-spacer devices. 相似文献
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Young Wook Park 《Thin solid films》2009,517(14):4108-4110
In this paper, we focused on the effects of the plasma treatment of the anode electrode of organic light emitting diodes (OLED) on the growth of hole-injection layer (HIL). The CF4 plasma (CF4-P) treatment, which is known for efficient method to enhance the performance of OLED, was not effective on the OLED with the HIL material copper phthalocyanine (CuPc). The CF4-P treated OLED showed remarkably reduced electroluminescence (EL) characteristics while the O2 plasma treated OLED showed improved EL efficiency. The dependence of the CuPc growth on the polarity of substrate induced the morphological difference of the HIL, and finally resulted in the different device characteristics. 相似文献