共查询到20条相似文献,搜索用时 62 毫秒
1.
Y.F. Xu 《Applied Surface Science》2006,252(6):2328-2333
In situ photoluminescence spectroscopy (PL) measurements of tris(8-hydroxyquinoline) aluminum (Alq3) film were carried out. Upon deposition of Alq3 on the glass substrate, the PL intensity changes dramatically, while the peak position of Alq3 emission shows a sharp red-shift from 524 nm at the initial deposition of Alq3, and tends to a saturation value of 536 nm for the film thickness range from 2 to 500 nm. This red-shift is associated with the change from the 2D to 3D exciton state with increasing Alq3 film thickness. Temperature dependent PL spectra of Alq3 films showed, besides the changes in the PL intensity, clearly a blue-shift of Alq3 emission about 9 nm for the film annealing up to 150 °C, while no any shift of Alq3 emission was observed for the film annealing below 130 °C. Both changes in PL intensity, and especially in the peak position of Alq3 emission were attributed to crystallization (thermal) effect of Alq3 film upon annealing. 相似文献
2.
The origination of ill-defined layer in organic spin valves was investigated by using atomic force microscopy (AFM) and Rutherford backscattering (RBS) analysis. It was found that conductive bulges of LSMO film and self-grown pinholes in Alq3 film other than Co inclusions could lead to the formation of ill-defined layer. The morphology of LSMO substrate had a strong influence on that of Alq3 film, LSMO/Alq3 and Alq3/Co interfaces. Moreover, Alq3 film with the thickness of 1-4 nm could be barriers which was explained by small active area and added insulated layer in organic magnetic tunnel junctions. 相似文献
3.
Yang Li 《Applied Surface Science》2008,254(22):7223-7226
Efficient tris-(8-hydroxyquinoline)aluminum (Alq3)-based organic light-emitting diodes (OLEDs) using YbF3 as the electron injection layer have been investigated. With an YbF3 (3.0 nm)/Al cathode, the device with Alq3 as the emitting layer achieved a better performance than the control device with a LiF (0.5 nm)/Al cathode. The release of the low-work-function metal Yb is responsible for the performance enhancement. From the analysis by atomic force spectroscopy and X-ray photoemission spectroscopy, it is observed that the Alq3-cathode interface could be well covered by YbF3 at an optimum thickness of 3.0 nm, which helps to prevent the contact between Alq3 and Al, and to reduce the destruction of Alq3 by Al. 相似文献
4.
Efficient white electroluminescence has been obtained by using an electroluminescent layer comprising of a blue fluorescent bis (2-(2-hydroxyphenyl) benzoxazolate)zinc [Zn(hpb)2] doped with red phosphorescent bis (2-(2′-benzothienyl) pyridinato-N,C3′)iridium(acetylacetonate) [Ir(btp)2acac] molecules. The color coordinates of the white emission spectrum was controlled by optimizing the concentration of red dopant in the blue fluorescent emissive layer. Organic light-emitting diodes were fabricated in the configuration ITO/α-NPD/Zn(hpb)2:0.01 wt%Ir(btp)2acac/BCP/Alq3/LiF/Al. The J-V-L characteristic of the device shows a turn on voltage of 5 V. The electroluminescence (EL) spectra of the device cover a wide range of visible region of the electromagnetic spectrum with three peaks around 450, 485 and 610 nm. A maximum white luminance of 3500 cd/m2 with CIE coordinates of (x, y=0.34, 0.27) at 15 V has been achieved. The maximum current efficiency and power efficiency of the device was 5.2 cd/A and 1.43 lm/W respectively at 11.5 V. 相似文献
5.
Efficient and stable single-dopant white OLEDs based on 9,10-bis (2-naphthyl) anthracene 总被引:1,自引:0,他引:1
Efficient white organic light-emitting diodes (WOLEDs) are fabricated with a thin layer of 9,10-bis (2-naphthyl) anthracene (ADN) doped with Rubrene as the source of white emission. A device with the structure of ITO/NPB (70 nm)/ADN: 0.5% Rubrene (30 nm)/Alq3 (50 nm)/MgAg shows a maximum current efficiency of 3.7 cd/A, with the CIE coordinates of x=0.33, y=0.43. The EL spectrum of the devices and the CIE coordinates remains almost the same when the voltage is increased from 10 to 15 V and the current efficiency remains quite stable with the current density increased from 20 to 250 mA/cm2. 相似文献
6.
Xiao-Wen Zhang Bing-Jie Mo Li-Ming Liu Hong-Hang Wang Dan-Teng Chang Ji-Wen Xu Hua Wang Bin Wei 《Current Applied Physics》2014,14(11):1460-1464
2-methyl-9,10-bis(naphthalen-2-yl)anthracene (MADN) based fluorescent blue organic light-emitting diodes (OLEDs) are demonstrated. With MADN as emitting layer, experiments indicate that thick MADN (40–60 nm) is preferable for constructing efficient blue OLED. With MADN as hole-transport and emitting layer and tris(8-hydroxy-quinolinato)aluminium (Alq3) as electron-transport layer, the OLED electroluminescent characteristics show a mixture emission of MADN and Alq3 with Commission Internationale d'Eclairage (CIE) color coordinates of (0.25, 0.34), indicating feasible hole transporting in MADN. Using 4,7-diphenyl-1,10-phenanthroline (BPhen) replacing Alq3 as electron-transport layer, the OLED shows deep blue emission with a maximum luminous efficiency of 4.8 cd/A and CIE color coordinates of (0.16, 0.09). The hole transport characteristics of MADN are further clarified by constructing hole-only device and performing impedance spectroscopy analysis. The results indicate that MADN shows superior hole-transport ability which is almost comparable to typical hole-transport material of N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine (NPB), suggesting a promising application for constructing efficient blue OLED with integrated hole-transport layer and emitting layer. 相似文献
7.
Two phosphorescent iridium(III) complexes (dfpmpy)2Ir(ppc) and (dfpmpy)2Ir(prz) [dfpmpy=2-(2′,4′-difluorophenyl)-4-methylpyridine, ppc=pipecolinate, prz=2-pyrazine carboxylate] were synthesized from the reaction of the chloro-bridged dimeric complex [(dfpmpy)2Ir(μ-Cl)]2 and the ancillary ligand. Their structures and photoluminescence properties were investigated and device performances for application in organic light-emitting diodes (OLEDs) were studied. The complexes adopt a distorted, octahedral geometry around the iridium metal, exhibiting cis C-C and trans N-N arrangements. The photoluminescent (PL) properties reveal that (dfpmpy)2Ir(ppc) emits in the blue-green region (λmax=497 nm), whereas (dfpmpy)2Ir(prz) shows red phosphorescence (λmax=543 nm) in the film state (5% wt. doped in PMMA). The (dfpmpy)2Ir(ppc)- and (dfpmpy)2Ir(prz)-based OLEDs exhibited sky-blue and greenish-yellow electroluminescence with similar current-voltage characteristics, repectively. Maximum current efficiency of (dfpmpy)2Ir(ppc) and (dfpmpy)2Ir(prz) were 4.4 and 7.4 cd/A, respectively. Maximum luminance values were approximately 10,000 cd/m2 for the both compounds. 相似文献
8.
In this study, the effect of one oxadiazole derivative (PBD) using as an electron injection layer (EIL) at Alq3/Cs2CO3 interface has been investigated. The present of PBD EIL was showed an interesting enhanced electron injection for OLEDs although the nominal electron injection barrier for PBD based OLEDs is much larger, because PBD owns an obvious higher intrinsic the Lowest Unoccupied Molecular Orbital level (2.3 eV) than that of Alq3 (3.0 eV). For example, the current density of OLEDs at 8 V was increased from 54 mA/cm2 to 168 mA/cm2 when inserting a thin PBD layer (5 nm) at Alq3/Cs2CO3 interface. Here the increased current is suggested associating with the changed electronic structure of PBD when it contacts with Cs2CO3. 相似文献
9.
White organic light-emitting devices (WOLEDs) with Mg:Ag/Alq3/Alq3:DCJTB/Alq3/DPVBi/α-NPD/ITO and Mg:Ag/Alq3/DPVBi:DCJTB/Alq3/DPVBi/α-NPD/ITO structures were fabricated with three primary-color emitters of red, green, and blue by using organic molecular-beam deposition. Electroluminescence spectra showed that the dominant white peak for the WOLEDs fabricated with host red-luminescence Alq3 and DPVBi layers did not change regardless of variations in the current. The Commission Inernationale de l'Eclairage (CIE) chromaticity coordinates for the two WOLEDs were stable, and the WOLEDs at 40 mA/cm2 with luminances of 690 and 710 cd/cm2 showed an optimum white CIE chromaticity of (0.33, 0.33). While the luminance yield of the WOLED fabricated with a host red-luminescent Alq3 emitting layer below 30 mA/cm3 was larger than that of the WOLED fabricated with a DPVBi layer, above 30 mA/cm2, the luminance yield of the WOLED fabricated with the DPVBi layer was higher than that of the WOLED with the Alq3 layer and became more stable with increasing current density. These results indicate that WOLEDs fabricated with a host red-luminescence DPVBi layer without any quenching behavior hold promise for potential applications in backlight sources in full-color displays. 相似文献
10.
Tianle Li Wenlian Li Xiao Li Zisheng Su Yiren Chen Zhiqiang Zhang 《Journal of luminescence》2010,130(10):1676-1679
Performances of red organic light-emitting device were improved by co-doping 2-formyl-5,6,11,12-tetraphenylnaphthacene (2FRb) and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetra-methyljulolidyl-9-enyl)-4H-pyran (DCJTB) in tris-(8-hydroxyquinoline) aluminum (Alq3) host as the emitting layer. The device with 1 wt% DCJTB and 2.4 w% 2FRb in Alq3 host gave a saturated red emission with CIE chromaticity coordinates of (0.65, 0.35) and a maximum current efficiency as high as 6.45 cd/A, which are 2 and 2.4 fold larger than that of the device with 1 wt% DCJTB (3.28 cd/A) in Alq3 host and the device with 2.4 wt% 2FRb (2.72 cd/A) in Alq3 host at the current density of 20 mA/cm2, respectively. The improvement could be attributed to the effective utilization of host energy by both energy transfer and trapping in the electroluminescence process and the depression of concentration quenching between the dopants molecules. 相似文献
11.
Shengyi Yang Yan Jiang Feng Teng Zheng Xu Yanbing Hou Xurong Xu 《Solid State Communications》2006,139(8):415-418
In this paper, the roles of zinc selenide (ZnSe) sandwiched between organic layers, i.e. organic/ZnSe/aluminum quinoline (Alq3), have been studied by varying device structure. A broad band emission was observed from ITO/poly(N-vinylcarbazole)(PVK)(80 nm)/ZnSe(120 nm)/ Alq3(15 nm)/Al under electric fields and it combined the emissions from the bulk of PVK, ZnSe and Alq3, however, emission from only Alq3 was observed from trilayer device ITO/N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1, 1′-biphenyl-4, 4′-diamine (NPB) (40 nm)/ZnSe(120 nm)/ Alq3(15 nm)/Al. Consequently the luminescence mechanism in the ZnSe layer is suggested to be charge carrier injection and recombination. By thermal co-evaporating Alq3 and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), we get white light emission with a Commission Internationale de l’E clairage (C.I.E) co-ordinates of (0.32, 0.38) from device ITO/PVK(80 nm)/ZnSe(120 nm)/ Alq3:DCJTB(0.5 wt% DCJTB)(15 nm)/Al at 15 V and the device performs stably with increasing applied voltages. 相似文献
12.
Irene Teresinha Santos Garcia Patrícia Velleda RibeiroDiogo Silva Corrêa Igor Michel Neto da CunhaNeftali Lenin Villarreal Carreño Eduardo Ceretta MoreiraFabiano Severo Rodembusch 《Applied Surface Science》2011,258(4):1437-1442
A photoactive complex based on europium(III) using the amino acid phenylalanine as ligand was prepared and characterized. The obtained europium(III)/phenylalanine complex presents an effective energy transfer from ligands to the rare earth center. The observed photoluminescent behavior for europium(III)/phenylalanine complex was similar to the well known europium(III)/ acetyl-β-acetonate hydrate. New photoactive polyamide thin films were prepared using polycaprolactam as host of these complexes. The structural characterizations of the films were studied through Rutherford backscattering (RBS), Fourier transform infrared (FTIR) and Raman spectroscopies. The polyamide films doped with the amino acid and acetyl-β-acetonate rare earth complexes maintain the original photoluminescent behavior, narrow emission bands corresponding to transitions 5D0 → 7F0-4, which indicates that this polymer is an excellent host to these complexes. 相似文献
13.
The optical properties including electronic absorption spectrum, emission spectrum, fluorescence quantum yield, and dipole moment of electronic transition of 7-diethylaminocoumarin (DEAC) laser dye have been measured in different solvents. Both electronic absorption and fluorescence spectra are red shifted as the polarity of the medium increases, indicating that the dipole moment of molecule increases on excitation. The fluorescence quantum yield of DEAC decreases as the polarity of solvent increases, a result of the role of solvent polarity in stabilization of the twisting of the intramolecular charge transfer (TICT) in excited state, which is a non-emissive state, as well as hydrogen bonding with the hetero-atom of dye. The emission spectrum of DEAC has also been measured in cationic (CTAC) and anionic (SDS) micelles, the intensity increases as the concentration of surfactant increases, and an abrupt change in emission intensity is observed at critical micelle concentration (CMC) of surfactant. 2×10−3 mol dm−3 of DEAC gives laser emission in the blue region on pumping with nitrogen laser (λex=337.1 nm). The laser parameters such as tuning range, gain coefficient (α), emission cross section (σe), and half-life energy have been calculated in different solvents, namely acetone, dioxane , ethanol, and dimethyforamide (DMF). The photoreactivity of DEAC has been studied in CCl4 at a wavelength of 366 nm. The values of photochemical yield (?c) and rate constant (k) are determined. The interaction of organic acceptors such as picric acid (PA), tetracyanoethylene (TCNE), and 7,7,8,8-tetracynoquinonedimethane (TCNQ) with DEAC is also studied using fluorescence measurements in acetonitrile (CH3CN); from fluorescence quenching study we assume the possible electron transfer from excited donor DEAC to organic acceptor forming non-emissive exciplex. 相似文献
14.
The optical absorption and photoluminescent spectra are studied in recently synthesized diphenyl pyrazoloquinolines (DPPQ): 1,3-diphenyl-1H-pyrazolo[3,4-b] quinoline and its 6-vinyl, 6-N,N-diphenyl, 6-methyl, 6-fluoro, 6-bromo and 6-chloro derivatives. The photoemission spectra are recorded in organic solvents of different polarity and found to be highly solvatochromic. The measured spectra are compared with the quantum chemical calculations performed by means of the semiempirical methods (AM1 or PM3) in combination with the equilibrium molecular conformation (EMC) in vacuo (T = 0 K, Γ = 0.12 eV) or MD simulations (T = 300 K). The broadening of absorption and emission bands and their red-shift with increasing of temperature may be well reproduced by MD simulations. The Stokes shift of the photoluminescent spectra is obtained by including vibrational modes into the emission equation. The quantum chemical method AM1 in combination with MD simulations gives in most cases the best agreement with the experimental data. By comparing the emission spectra of 6-N,N-diphenyl-DPPQ with other DPPQ-derivatives one concludes that the molecular fragment diphenyl-amin [(C6H5)2N-] is likely subjected to strong conformational changes in solvents. The large difference between the excited- and state-dipole moments indicates on a strong electron transfer effect being common for all DPPQ derivatives. 相似文献
15.
The multilayer organic light-emitting diodes (OLEDs) have been fabricated with a thin alkaline metal chloride layer inserted inside an electron transport layer (ETL), tris (8-hydroxyquinoline) aluminum (Alq3). The alkaline metal chloride layer was inserted inside 60 nm Alq3 at d=0, 10, 20 and 30 nm positions (d is the distance of the interlayer away from the Al cathode). The devices, with alkaline metal chlorides inserted at the Alq3/Al interface, showed electron injection and electroluminescence (EL) intensity improvements. When the alkaline metal chlorides were inserted inside the Alq3 layer at 10, 20 or 30 nm position apart from the Al cathode, both EL intensity and efficiency were enhanced for the devices with a thin potassium chloride (KCl) or rubidium chloride (RbCl) layer. On the contrary, the improvements were not observed for the OLEDs with a thin sodium chloride (NaCl) layer. A proposed insulator buffer layer model is employed to explain these characteristics of the devices. 相似文献
16.
Po-Hsun Lei Shun-Hsi Wang Fuh Shyang Juang Yung-Hsin Tseng Meng-Jung Chung 《Optics Communications》2010,283(9):1933-1937
In this article, we report on the effect of SiO2/Si3N4 dielectric distributed Bragg reflectors (DDBRs) for Alq3/NPB thin-film resonant cavity organic light emitting diode (RCOLED) in increasing the light output intensity and reducing the linewidth of spontaneous emission spectrum. The optimum DDBR number is found as 3 pairs. The device performance will be bad by further increasing or decreasing the number of DDBR. As compared to the conventional Alq3/NPB thin-film organic light emitting diode (OLED), the Alq3/NPB thin-film RCOLED with 3-pair DDBRs has the superior electrical and optical characteristics including a forward voltage of 6 V, a current efficiency of 3.4 cd/A, a luminance of 2715 cd/m2 under the injection current density of 1000 A/m2, and a full width at half maximum (FWHM) of 12 nm for emission spectrum over the 5-9 V bias range. These results represent that the Alq3/NPB thin-film OLED with DDBRs shows a potential as the light source for plastic optical fiber (POF) communication system. 相似文献
17.
A very stable and blue luminescent complex Zn(bbp)Cl2 (bbp: 2,6-bis(benzimidazolyl)pyridine) was synthesized. X-ray crystal structural analysis for the complex revealed that there are intermolecular π?π interactions in the solid state. The fluorescence properties for this complex were studied. The similar devices with the structure of [ITO/CuPc(31 nm)/NPB(80 nm)/[Zn(bbp)Cl2] (or L) (85 nm)/LiF15/Al] were constructed to investigate their electroluminescent performance. Both the complex and the ligand can be fabricated as blue-emitting materials. The complex shows emission peak at 555 nm, electroluminescent efficiency 0.017 cd A−1 and turn-on voltage 7 V, compared to 470 nm, 0.036 cd A−1 and 9 V for the ligand. 相似文献
18.
Efficient white organic light-emitting devices using 4,7-diphenyl-1,10-phenanthroline as block layer
A white light-emitting device has been fabricated with a structure of ITO/m-MTDATA (45 nm)/NPB (10 nm)/DPVBi (8 nm)/DPVBi:DCJTB 0.5% (15 nm)/BPhen (x nm)/Alq3 [(55−x) nm]/LiF (1 nm)/Al, with x=0, 4, and 7. BPhen was used as the hole-blocking layer. This results in a mixture of lights from DPVBi molecules (blue-light) and DCJTB (yellow-light) molecules, producing white light emission. The chromaticity can be readily adjusted by only varying the thickness of the BPhen layer. The CIE coordinates of the device are largely insensitive to the driving voltages. When the thickness of BPhen is 7 nm, the device exhibits peak efficiency of 6.87 cd/A (3.59 lm/W) at the applied voltage of 6 V, the maximum external quantum efficiency ηext=2.07% corresponding to 6.18 cd/A, and the maximum brightness is 18494 cd/m2 at 15 V. 相似文献
19.
Organic light-emitting diodes were fabricated with a structure of indium-tin-oxide (ITO)/poly(N-vinylcarzole)(PVK):4-(dicyanom-ethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB)/8-tris-hydroxyquinoline aluminum (Alq3)/lithium fluoride (LiF)/Al. The energy transfer from PVK to Alq3 then to DCJTB and the charge trapping processes were investigated by employing the photoluminescence (PL) and electroluminescence (EL) spectra. With increasing thickness of the Alq3 layer, the PL and EL emission from PVK were decreased gradually, which indicated that the effective energy transfer occurred from PVK to Alq3 and then from Alq3 to DCJTB. At the same time, we found that the exciton recombination zone could be adjusted by controlling the Alq3 layer thickness and the applied voltages. The effects of different DCJTB concentrations on the optical and electrical characteristics of the devices were investigated, and an obvious red-shift was observed with the DCJTB dopant concentrations increasing in the PL and EL spectra. 相似文献
20.
A mononuclear Sm(III) complex involving Pic and EO4 (where Pic=picrate anion and EO4=tetraethylene glycol) has been studied. It shows a bright-orange emission when used as active material in a monolayer electroluminescent device of ITO/EO4-Sm-Pic/Al. The crystal structure of the complex consists of [Sm(Pic)2(H2O)(EO4)]+ cation and [Pic]− anion. The Sm(III) ion is coordinated with nine oxygen atoms from one EO4 ligand in a pentadentate mode, two Pic anions each in bidentate and monodentate modes, and one water molecule. Both the terminal alcohol groups of the acyclic EO4 ligand were involved in the O-H…O hydrogen bonding by infinite one-dimensional (1D) chain within a symmetry direction [0 1 0]. The photoluminescence (PL) spectrum of the thin film shows the typical spectral features of the Sm(III) ion (4G5/2→6H7/2 transitions). The root-mean-square (rms) of the roughness of thin film is 30.605 nm and indicates that the formation of the monolayer electroluminescent device is not uniform and retains a high crystallinity. Typical semiconductor current-voltage (I-V) property was also observed in this device with threshold and turn voltages of 2.8 and 6.2 V, respectively. The [Sm(Pic)2(H2O)(EO4)](Pic)·H2O complex can be applied as a luminescent center in OLED for bright-orange emission. 相似文献