不同空穴注入电极对有机薄膜电致发光性能的影响

成功地制备了用铝掺杂的氧化锌（ＡＺＯ）透明导电膜作阳极的有机薄膜电致发光器件，并对单层和双层结构的ＡＺＯ器件以及以两种不同ＩＴＯ作阳极器件的电致发光光谱，电流电压特性，亮度电压特性以及电致发光量子效率进行了详细的比较分析和讨论。     

ZnS:Mn沉积温度对薄膜电致发光器件亮度的影响

采用丝网印刷技术,在Al2O3陶瓷基板上印刷、高温烧结内电极及绝缘层,制备出陶瓷厚膜基板,进而制备了新型厚膜电致发光显示器(TDEL).整个器件结构为陶瓷基板/内电极/厚膜绝缘层/发光层/薄膜绝缘层/ITO透明电极.研究不同基板沉积温度对发光层性能的影响,并对器件的亮度-电压、亮度-频率进行测量.结果显示较高的ZnS:Mn沉积温度明显提高了无机发光器件的发光亮度.其原因主要是由于高的沉积温度提高了ZnS:Mn的成膜质量,提高膜层微晶尺寸大小,从而发光亮度提高.但是我们发现温度继续提高的同时,器件发光亮度趋于饱和,分析原因是由于掺杂Mn浓度过高,影响了发光效果.     

以N—乙基—4—乙酰胺基—1,8—萘亚胺为发光层的电致发光二极管

合成了Ｎ乙基４乙酰胺基１，８萘亚胺（ＮＡ）。结果表明，以ＮＡ为发光层，聚乙烯咔唑（ＰＶＫ）为空穴传输层的多层薄膜发光器件Ａｌ／ＮＡ／ＰＶＫ／ＩＴＯ，在正相驱动电压为２７５Ｖ时，可获得１５０ｃｄ／ｍ２的Ｎ乙基４乙酰胺基１，８萘亚胺（ＮＡ）的黄绿光。     

Novel green-emitting polymer containing fluorene and 1-(2-benzothiazolyl)-3,5-diphenylpyrazoline

Novel electroluminescent (EL) polymer based on fluorene having benzothiazolylpyrazoline unit in the main chain was synthesized. The result polymer possessed satisfactory thermal stability with onset decomposition temperature (T _d) of 401 °C and glass-transition temperature (T _g) of 213 °C. The polymer emits green fluorescence with high photoluminescence (PL) quantum yield of 47%. Polymer light-emitting diode (PLED) was fabricated with the configuration of ITO/PEDT 40 nm/PVK 40 nm/polymer(80 nm)/Ba(4 nm)/Al(160 nm) showed turn-on voltage of 4.5 V, and it can emit green light with maximum brightness of 1726 cd m⁻² with the maximum external quantum efficiency of 1.59%.     

Organic light-emitting devices fabricated utilizing core/shell CdSe/ZnS quantum dots embedded in a polyvinylcarbazole

Electrical and the optical properties of organic light-emitting devices (OLEDs) fabricated utilizing core/shell CdSe/ZnS quantum dots (QDs) embedded in a polyvinylcarbazole (PVK) layer were investigated. An abrupt increase of the current density above an applied voltage of 12 V for OLEDs consisting of Al/LiF/4,7-diphenyl-1,10-phenanthroline/bis-(2-methyl-8-quinolinolate)-4-(phenylphenolato) aluminium/[CdSe/ZnS QDs embedded in PVK]/poly(3,4-ethylenedioxythiophene) and poly(styrenesulfonate)/ITO/glass substrate was attributed to the existence of the QDs. Photoluminescence spectra showed that the peaks at 390 and 636 nm corresponding to the PVK layer and the CdSe/ZnS QDs were observed. While the electroluminescence (EL) peak of the OLEDs at low voltage range was related to the PVK layer, the EL peak of the OLEDs above 12 V was dominantly attributed to the CdSe/ZnS QDs. The Commission Internationale de l’Eclairage (CIE) chromaticity coordinates of the OLEDs at high voltages were (0.581, 0.380) indicative of a red color. When the holes existing in the PVK layer above 12 V were tunneled into the CdSe/ZnS QDs, the holes occupied by the CdSe/ZnS QDs combined with the electrons in the PVK layer to emit a red color related to the CdSe/ZnS QDs.     

Spectroscopic and TEM studies on poly vinyl carbazole/terbium complex and fabrication of organic electroluminescent device

Terbium acetyl salicylate complex containing 1,10-phenanthroline was synthesized. Element analysis showed that the composition of the complex was Tb(C₉O₄H₇)₃(C₁₂N₂H₈). A single layer electroluminescent device using polyvinyl carbazole doped with the terbium complex as an emitting layer was fabricated. The device showed bright green EL emission. The dispersion of the terbium complex in PVK matrix was investigated using transmission electron microscopy.     

Synthesis and characterization of new 3-alkylthiophene copolymer that exhibit orange-red photoluminescence and electroluminescence

Using copolymerization functionalization, a Novel solution-processable π-conjugated 3-alkylthiophene copolymer (molar ratio of monomer 3-octylthiophene (3OT) and 3-(2-ethyl-1-hexyl) thiophene (3EHT) was 1:1) combining electrochemical properties of poly (3-octylthiophene) (P3OT) and poly (3-isooctylthiophene) (P3EHT) was synthesized by FeCl₃-oxidative approach. Characterization of the polymers included FT-IR, NMR, gel permeation chromatography (GPC), thermo-gravimetric analysis (TGA), UV-Vis spectroscopy photoluminescence (PL) and electroluminescence (EL). P3OTEHT depicted excellent solubility in common organic solvents. The optical properties investigations showed that the band-gap energy of P3OTEHT was similar to P3OT (2.43 eV) at 2.45 eV and 6% lower than that of P3EHT in CHCl₃ solution. The emission maxima of P3OTEHT was 50 nm blue-shifted with respect to that of P3OT. However, the PL intensity of P3OTEHT was seven times higher than that of P3OT in film. The turn-on voltage of LED (ITO/P3OTEHT/Ag) devices was approaching to P3OT (5.5 V) at 5.6 V and 1.9 V lower than that of P3EHT. The EL color of P3OTEHT was bright pure orange-red (emission λ_max^EL of 600 nm), meanwhile, the half-wave bandwidth was 70 nm. TGA studies showed that P3OTEHT exhibited very good thermal stabilities, losing 5% of its weight on heating to 300 °C. The results indicate that the P3OTEHT with low band-gap energy, low turn-on voltage, high photoluminescence quantum yield pure EL color and processability, and might be promising polymer materials for applications in polymer light-emitting diodes, light-emitting electrochemical cells and polymer solar cells, etc.     

Polymer light-emitting devices based on plasma-polymerized benzene and plasma-polymerized naphthalene

Polymer light-emitting devices (PLED) were fabricated utilizing plasma-polymerized benzene (PPB) and plasma-polymerized naphthalene (PPN) as an electroluminescent (EL) emitting layer. The plasma polymerization is well suited for forming the transparent, sturdy thin film for EL polymer layers. For the ITO/PPB/Al and ITO/PPN/Al devices, the turn-on voltage of the device was at 12V and 6V, respectively. The luminance of the PPB device reached 6 cdm ^-2 at 10 V, whereas the PPN device reached 11 cd m ^-2 at 14 V. The external quantum efficency was 0.0035% for the PPB device and 0.0056% for the PPN device. The dense crosslinked structure formed by the plasma polymerization makes the EL device relatively stable during operation. © 2001 Kluwer Academic Publishers     

Relationship between structure and electroluminescence of oligo(p-phenylenevinylene)s

The preparation of LEDs with poly( p-phenylenevinylene) (PPV) as emitting material is well established. However, due to the presence of a distribution of conjugated chain lengths in the polymer, systematic investigations of the electroluminescence with polymeric materials are difficult, as far as the optical emission is concerned. We are studying the relationship between structural variation of substituted oligo(p-phenylenevinylene)s and their electroluminescent behaviour using a series of distyrylbenzenes with a variety of substituents in order to investigate their influence on the electroluminescence (EL). Furthermore, we synthesized a homologous series of monodisperse oligo(2,5-dipropoxy-1,4-phenylenevinylene)s with up to 11 repeating units. This series covers the spectrum from monomer to polymer. The influence on the EL can be investigated by preparing single layer LEDs using vapor deposition or spincoating of the oligomers in a polystyrene (PS) matrix. The comparison of photoluminescence (PL)- and EL-spectra shows that the photophysical properties of the oligomers are strongly altered by aggregation phenomena.     

用稀土金属Eu的有机配合物Eu(DBM)_2(AA)phen作发光层的有机电致发光薄膜的研究

研究了稀土Eu的有机配合物Eu(DBM ) 2 (AA) phen的光致发光特性。用Eu(DBM) 2 (AA) phen作发光层 ,分别用N ,N 双 (3 甲苯 ) N ,N 二苯联苯胺 (TPD)和聚乙烯基咔唑 (PVK)作空穴传输层研制了有机电致发光薄膜器件 ,研究了它们的电致发光特性     

Investigation of electroluminescence properties of CdTe@CdS core-shell nanocrystals (NCs)

In this work, CdTe@CdS NCs were synthesized using a thermochemical approach and synthesized NCs were used as an emissive layer, a light emitting device, with ITO/MoO₃/PVK/CdTe@CdS(core-shell)/Mg:Ag structure. Structural and optical properties of synthesized NCs were investigated by means of XRD, UV–Vis and photo-luminescence (PL) analyses. Fabricated device was characterized by electroluminescence spectra. XRD analysis demonstrated cubic phase NCs. Photoluminescence spectra showed a narrow band emission with a peak centred at about 600 nm. Fabricated device showed an emission at 600 nm, which is related to CdTe@CdS NCs. Turn on voltage of fabricated device is about 8 V and brightness is 53·7 Cd/m² at a working voltage of about 14·57 V.     

水溶胶CdSe纳米复合器件电致发光特性的研究

以巯基乙酸为稳定剂在水相中制备了水溶胶CdSe纳米晶,透射电子显微镜表明了纳米晶的形态和尺寸大小.用表面活性剂将CdSe纳米晶从水相中转移到有机相中,将其与具有空穴传输性能的聚合物PVK互溶在一起作为电致发光器件的发光层,以Alq3作为电子传输层,在发光层与Alq3之间加入了空穴阻挡层BCP制备了多层电致发光器件,研究了不同CdSe/PVK配比下水溶胶CdSe纳米复合器件的电致发光特性,结果发现随着水溶胶CdSe纳米晶在纳米复合物中所占比例的降低,电致发光器件的发光强度有所提高,起亮电压有所降低.     

Influence of surface electrode on luminescent properties of nanocrystalline silicon electroluminescent device

We describe the electrical and luminescence properties of nanocrystalline silicon (nc-Si) based red electroluminescent (EL) devices using an indium tin oxide (ITO) and/or gold (Au) films as a surface electrode, and the variation in the transmittance and resistivity of two electrodes with various film thicknesses. The increase in the film thickness from 50 to 200 nm of the ITO electrode led to the lowering of resistivity from 2.0 x 10(-3) to 9.1 x 10(-4) omega cm and almost the same value (83-92%) of transmittance in the red region. On the other hand, the Au electrode was lowered the resistivity from 1.8 x 10(-4) to 1.6 x 10(-5) omega cm and the transmittance in the red region from 42 to 1.8% with increasing the film thickness from 10 to 80 nm. Moreover, the red luminescence from the EL devices using the ITO and/or Au electrodes having thickness of 200 and 10 nm, respectively, obtained by applying the direct current forward voltage above 4.5 and 2.5 V and/or by flowing the forward current density above 53 and 38 mA/cm2, respectively. However, the luminescence intensity of EL device with the ITO electrode strengthened more than about one order of magnitude in comparison to that of the EL device with the Au electrode. This was due to the high value of transmittance in the red region of the ITO electrode. We suggest that the ITO electrode is an optimum surface electrode for the realization of nc-Si based EL device with the high brightness.     

Fabrication and characterization of organic light-emitting diodes using zinc complexes as hole-blocking layer

2-(2-Hydroxyphenyl)benzoxazole (HPB) was employed as organic ligand and the corresponding zinc complexes (Zn(HPB)2 and Zn(HPB)q) were synthesized. And their EL properties were characterized. The structures of zinc complexes were determined with FT-NMR, FT-IR, UV-Vis, and XPS. The thermal stability showed up to about 300 degrees C under nitrogen flow, which was measured by TGA. The photoluminescence (PL) of zinc complexes were measured from the DMF solution. The PL emitted in blue and yellow region, respectively. The EL devices were fabricated by the vacuum deposition. Two kinds of OLEDs devices were fabricated; ITO/NPB (40 nm)/Zn complexes (60 nm)/LiF/Al and ITO/NPB (40 nm)/Alq3 (60 nm)/Zn complexes (5 nm)/LiF/Al. Both of the EL properties as the emitting and the hole-blocking layer were investigated. The EL emission of Zn(HPB)q exhibited green light centered at 532 nm. The device showed a turn-on voltage at 5 V and a luminance of 6073 cd/m2 at 10 V. Meanwhile, the maximum EL the emission of the Zn(HPB)2 device was found to be at 447 nm. And the device showed a luminance of 2813 cd/m2 at 10 V. The ITO/NPB (40 nm)/Alq3 (60 nm)/Zn(HPB)2 (5 nm)/LiF/Al device showed increased luminance of L=17000 cd/m2 compared to L=12000 cd/m2 for similar device fabricated without the hole-blocking layer. And the turn-on voltage was significantly affected by the existence of the hole-blocking layer.     

聚单乙氧基萘乙炔（PEONV）的电致发光特性

用可溶性前聚物法制备了单乙氧基取代的聚1．4萘乙炔（PEONV）。并采用PEONV作为有源层制作了单层结构电致发光器件。该器件的阳极为ITO，阴极为Ca，器件在正向偏压4V时开始发光，发光谱峰值605nm。最高亮度为156cd／m2。发光峰与未取代的PNV器件相比没有明显变化。文章对此作出了初步解释。     

Bisphenol A based pyrazoloquinoline dimers as dopants for electroluminescent applications

A series of 1,3-methyl/phenyl (1,3-Me/Ph) bisphenol A based pyrazoloquinoline dimers (BAPQD) have been synthesized and characterized by spectroscopic methods. The obtained results demonstrate that recently synthesized dyes may be considered as promising materials for electroluminescent applications being used as dopants of PVK layers in OLED fabrication. The electroluminescent devices of the structure (ITO)/PVK:BAPQD-X/Ca/Al (X = 1–4) have been constructed and their current-voltage-luminescence characteristics are derived. In PVK host the 1,3-Me/Ph BAPQD derivatives emit light with different shades of blue color.     

ZnS:Cu polymer nanocomposites for thin film electroluminescent devices

Copper-doped zinc sulphide nanoparticles with varying copper content were synthesized via a coprecepitation method and embedded in polymer thin films by phase transfer technique to examine direct current electroluminescence (DC-EL) properties. A single layer structure (ITO/ZnS:Cu@ polymer/Al) was chosen to examine the influence of film thickness, copper content and polymeric matrix. Two types of devices were investigated based either on an insulating polymethylmethacrylate (PMMA) matrix or a semiconducting poly(9-vinylcarbazole) (PVK) matrix. The resulting DC-EL differs in spectral characteristics showing a broad EL emission over the whole visible range for PMMA based devices and EL with narrow full width at half-maxima values (FWHM) and maxima positions close to those observed in photoluminescence (PL) spectra of particle dispersions.     

Preparation and characterization of regioregular poly(3-octylthiophene-2,5-diyl)/copper indium disenillide/titania heterojunction polymer solar cells

By optimizing the P3OT/CISe ratio, TiO₂ content in the P3OT/CISe active layer, annealing temperature and time, this study investigated hybrid Al/Ca/P3OT:CISe:TiO₂/PEDOT:PSS/ITO thin film solar cells with improved efficiency. Due to an increase in charge-carrier transport and a decrease of electron-hole recombination, it is possible to increase the efficiency of hybrid solar cells by adding TiO₂ nanoparticles to the P3OT:CISe active film. Also, performance enhancement of the solar cells can occur with an increase of CISe content in P3OT as well as the addition of a PEDOT:PSS layer to the cell structure. The optimum TiO₂ content in P3OT:CISe layer is 15 wt.%. The optimum annealing temperature and time are 125 °C and 30 min, respectively. The formation of large CISe and TiO₂ aggregates that reduce charge mobility may cause the decrease of efficiency. The rough surface may effectively reduce the charge-transport distance and provide nanoscale phase separation that further enhances internal light scattering and light absorption. The best results for the open circuit voltages (V_oc), short-circuit current density (J_sc), fill factor (FF), and efficiency (η_e) of Al/Ca/POCT15/PEDOT:PSS/ITO hybrid solar cells obtained at optimized conditions were V_oc = 0.49, J_sc = 3.20, FF = 42.96, and η_e = 0.674, respectively.     

Structural effects of a light emitting copolymer having perylene moieties in the side chain on the electroluminescent characteristics

We have synthesized a novel side chain light emitting copolymer. The side chain light emitting copolymer has a perylene moiety as an emitting unit and methylmethacrylate (MMA) as a spacer to decrease the concentration quenching of light emitting site in the polymer intrachain. These polymers are very soluble in most organic solvents such as monochlorobenzene, tetrahydrofuran, chloroform and benzene. The single-layered electroluminescent (EL) device consisting of ITO/carrier transporting copolymer and light emitting copolymer/Al was manufactured. The carrier transporting copolymer has triphenylamine moiety as a hole transporting unit and triazine moiety as an electron transporting unit in the polymer side chain. This device exhibits maximum external quantum efficiency when the MMA contents of light emitting copolymer is 30 wt.%. In particular, the device emits more blue light as MMA contents increase.     

Effect of the ligand on the properties of emitting materials: Pentacoordinated 8-hydroxyquinoline aluminum complexes

Two series of pentacoordinated complexes, AlMq₂q′ and Alq₂q′ (q is 8-hydroxyquinoline, Mq is 2-methyl-8-hydroxyquinoline and q′ is phenolato ligand), were synthesized, and assessed as potential emitting materials in thin film (photoluminescence, PL) and electroluminescent (EL) device. EL devices with a configuration of ITO/NPB(50 nm)/Complex(50 nm)/Mg/Ag(10:1) were fabricated. Strong blue and green emission were observed from thin solid film and EL device of AlMq₂q′ and Alq₂q′, respectively. The results revealed that the PL and EL emission wavelengths of these materials are primarily determined by Mq and q (first ligand), whereas phenolato ligand (second ligand) has little effect on the emission wavelength but remarkable influence on EL efficiency.