一种用于堆叠结构有机发光二极管的新的电荷生成层

本文报道了一种用于堆叠结构有机电致发光器件的新的电荷生成层: LiF/Al/V₂O₅,采用这种电荷生成层的堆叠器件的两个发光单元互相独立,不受影响.说明在外加电场下,这种电荷生成层具有向邻近的发光单元注入电子空穴的能力.而堆叠了两个相同发光单元的器件的电流效率在相同的电流密度下约为普通单层结构的1.7倍.同时这种电荷生成层避免了溅射indium tin oxide(ITO)和金属、有机物共掺,只需要热蒸发,生长工艺简单. 关键词： 堆叠结构 有机电致发光器件 电荷生成层     

n-type ZnS used as electron transport material in organic light-emitting diodes

This paper reports on the n-type ZnS used as electron transport layer for the organic light-emitting diodes (OLEDs). The naphthyl-substituted benzidine derivative (NPB) and tris (8-hydroxyquinoline) aluminium (AlqOLEDs n型ZnS 电子运输层 亮度 效率 功能发光二极管OLEDs, n-type ZnS, electron transport layer, luminance, efficiencyProject supported by the National Natural Science Foundation of China (Grant No 60476005), the Scientific Research Foundation for Returned Overseas Chinese Scholars, the State Education Ministry, the State Key Program for Basic Research of the Ministry of Science and Technology of China (Grant No 2003CB314707), and the Key Project of National Natural Science Foundation of China (Grant No 50532090).2005-11-211/9/2006 12:00:00 AMThis paper reports on the n-type ZnS used as electron transport layer for the organic light-emitting diodes （OLEDs）. The naphthyl-substituted benzidine derivative （NPB） and tris （8-hydroxyquinoline） aluminium （Alq3） are used as the hole transport layer and the emitting layer respectively. The insertion of the n-type ZnS layer enhances the electron injection in the OLEDs. The study was carried out on OLEDs of structures： indium-tin-oxide （ITO）/NPB/Alq3/ZnS/LiF/AL, ITO/NPB/Alq3/LiF/AL and ITO/NPB/Alq3/AL. The luminance and efficiency of the device containing this electron transport layer are increased significantly over those obtained from conventional devices due to better carrier balance.     

High-efficiency organic light-emitting diodes based on ultrathin blue phosphorescent modification layer

Yellow organic light-emitting devices(YOLEDs) with a novel structure of ITO/MoO_3(5 nm)/NPB(40 nm)/TCTA(15 nm)/CBP:(tbt)_2Ir(acac)(x%)(25 nm)/FIrpic(y nm)/TPBi(35 nm)/Mg:Ag are fabricated. The ultrathin blue phosphorescent bis[(4,6-difluorophenyl)-pyridi-nato-N,C2■](picolinate) iridium(Ⅲ)(FIrpic) layer is regarded as a highperformance modification layer. By adjusting the thickness of FIrpic and the concentration of (tbt)_2Ir(acac), a YOLED achieves a high luminance of 41618 cd/m~2, power efficiency of 49.7 lm/W, current efficiency of 67.3 cd/A, external quantum efficiency(EQE) of 18%, and a low efficiency roll-off at high luminance. The results show that phosphorescent material of FIrpic plays a significant role in improving YOLED performance. The ultrathin FIrpic modification layer blocks excitons in EML. In the meantime, the high triplet energy of FIrpic(2.75 eV) alleviates the exciton energy transport from EML to FIrpic.     

Enhancing properties of organic light-emitting diodes with LiF inside the hole transport layer

A new device has been made by inserting thin LiF layer in N,N′-diphenyl-N,N′-bis(1-napthyl–phenyl)-1, 1′-biphenyl-4,4′-diamine (NPB), which has a configuration of ITO/NPB(20 nm)/LiF(0.5 nm)/NPB(20 nm)/Alq₃(60 nm)/LiF(0.5 nm)/Al. Compared with normal device, the device inserted LiF layer inside NPB (HTL) can improve its performance. The luminance and efficiency is about 1.4 and 1.3 folds high of the conventional structure, respectively. The suggestion mechanism is that the LiF in the NPB layer can block holes of NPB, and balance the holes and electrons. Consequently, there are more excitons formed to boost the diode’s luminance and efficiency. And it may offer some valuable references for OLED’s structure.     

使用PTB7作为阳极修饰层提高有机发光二极管的性能

采用poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl][3-?uoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]](PTB7)作为有机发光二极管器件的阳极修饰层,制备了结构为indium tin oxide(ITO)/PTB7(不同浓度)/N,N’-Bis(naphthalen-1-yl)-N,N’-bis(phenyl)benzidine(NPB,40 nm)/8-hydroxyquinoline(Alq3,60 nm)/LiF(1 nm)/Al的系列器件,同时研究了不同浓度的PTB7对器件性能的影响.PTB7的最佳浓度为0.25 mg/mL,器件性能得到明显的改善,起亮电压为4.3 V.当驱动电压为14.6 V时,最大亮度为45800 cd/m2,最大电流效率为9.1 cd/A.与没有PTB7修饰的器件相比,其起亮电压降低了1.9 V,最高亮度提升了78.5%.器件性能提高归因于PTB7的插入使得空穴注入和传输能力大大改善.     

Effect of net carriers at the interconnection layer in tandem organic solar cells

Tandem cell with structure of indium tin oxide (ITO)/molybdenum oxide (MoO₃)/fullerene (C60)/copper phthalocyanine (CuPc)/C60/tris-8-hydroxy-quinolinato aluminum (Alq₃)/Al was fabricated to study the effect of net carriers at the interconnection layer. The open circuit voltage and short circuit current were found to be 1.15 V and 0.56 mA/cm², respectively. Almost the same performance (1.05 V, 0.58 mA/cm²     

基于ZnS增透膜的顶发射白光有机发光二极管

顶发射白光有机发光二极管(TEWOLED)在白光照明和全彩显示中有着良好的应用前景, 克服顶发射器件中的微腔效应是制备光电性能良好的TEWOLED的前提. 使用具有高折射率的ZnS作为增透膜改善金属阴极在蓝光波段的透射率,降低其反射性, 从而有效抑制了微腔的影响.同时利用转移矩阵理论和宽角干涉方法分别对阴极结构和 蓝光发光层位置进行了优化,最终获得了高效、色纯度良好、色度随视角变化小的TEWOLED. 最高亮度和效率分别达到9213 cd/m²和3 cd/A,色坐标位于白光区且接近白光等能点, 同时具有良好的视角稳定性,在0°---60°范围内色坐标仅变化(0.02, 0).     

Solution-processed p-doped hole-transport layer and its application in organic light-emitting diodes

We investigate p-type doping poly(9-vinylcarbazole) (PVK) hole-transport layer (HTL) with tetrafluoro-tetracyano-quinodimethane introduced via cosolution. We found that the performances of devices with doped HTLs are significantly improved. The efficiency and lifetime of the p-doped device are 2.3 and 3.7 times as large as that of the control device with pure PVK as a HTL. Furthermore, the turn-on voltage of the device is reduced from 9.5 to 3.6 V by using a p-doped HTL. These improved properties are attributed to the formation of the charge-transfer complex in the HTL, which increases hole injection and conductivity of p-doped films considerably.     

Co50Fe50-xSix合金的结构相变和磁性

利用实验测量和理论计算相结合的方法,研究了介于B2结构CoFe低有序合金和L2₁结构Co₂FeSi高有序合金之间的Co₅₀Fe_50-xSi_x合金的结构相变、磁相变、分子磁矩和居里温度.采用考虑Coulomb相互作用的广义梯度近似(GGA+U)方法计算了合金的能带结构.研究发现,合金出现较强的原子有序倾向,表现出较强的共价成相作用.合金的晶格常数、磁矩、居里温度随Si含量的增加而线性地降低,极限成分Co₂FeSi合金的分子磁矩和居里温度分别达到5.92μ_B和777 ℃.原子尺寸效应导致合金晶格发生变化,但并未成为居里温度和分子磁矩变化的主导因素.分子磁矩的变化符合Slater-Pauling原理,但发现原子磁矩的变化并非线性,据此提出了共价成相对磁性影响的观点.采用Stearns理论解释了居里温度的变化趋势,排除了原子间距对居里温度的主导影响作用.能带计算的结果还表明,Co₂FeSi作为半金属材料并非十分完美,可能在实际应用中会出现自旋极化率降低的问题.发现该系列合金的结构相变和磁相变随着成分的变化聚集在窄小的成分和温度范围内. 关键词： 磁性 Heusler合金 结构相变     

Effects of hole injection layer thickness on the luminescent properties of white organic light-emitting diodes

This work investigates how the thickness of the hole injection layer (HIL) influences the luminescent characteristics of white organic light-emitting diodes (WOLED). Experimental results indicate that inserting a thin HIL (<200 Å) into a WOLED without an HIL reduces the brightness and clearly changes the chromaticity because the surface of the 4,4′,4″-tris{N,-(3-methylphenyl)-N-phenylamino}-triphenylamine) (m-MTDATA) film is extremely rough. In contrast, a dense film structure and the fine surface morphology of m-MTDATA of moderate thickness (350-650 Å) provides a uniform conducting path on which holes cross the indium tin oxide (ITO)/HIL interface, improving luminescent performance, associated with the relatively stable purity of the color of the emission, with Commission Internationale 1′Eclairage (CIE) coordinates of (x = 0.40, y = 0.40). However, inserting a thick HIL (>650 Å) reduces the luminescent performance and causes red-shift, because the holes and electrons in the effective emissive confinement region become less optimally balanced. Moreover, optimizing the device structure enables a bright WOLED with CIE coordinates of (x = 0.34, y = 0.33) to reach a luminance of 7685 cd/m² at a current density of 100 mA/cm², with a maximum luminous efficiency of 1.72 lm/W at 5.5 V.     

Modification of anode surface in organic light-emitting diodes by chalcogenes

Influence of thin chalcogen X (S, Se, Te) interlayer between anode (indium-tin oxide, ITO) and a layer of N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD) used as a hole-transport layer (HTL) on the operating characteristics of organic light-emitting diodes (OLEDs) of composition ITO/X/TPD/Alq₃/Yb (Alq₃ - aluminum 8-quinolinolate) has been investigated. It was found that the sulphur layer decreases operating voltage and enhances operating stability of a device while the selenium or tellurium interlayers impair these characteristics.     

High performance polymer light-emitting diodes doped with a novel phosphorescent iridium complex

High performance polymer light-emitting diodes (PLEDs) based on a phosphor of noble metal complex bis(1,2-dipheny1-1H-benzoimidazole) iridium (acetylacetonate) [(pbi)₂Ir(acac)] doped in poly(N-vinylcarbazole) (PVK) host with various concentration were demonstrated. The photoluminescence (PL) and electroluminescence (EL) spectra of the PLEDs exhibited an emission intensity decrease of PVK and a gradually enhanced feature of (pbi)₂Ir(acac) with increased doping concentration. The device with a 5 wt% (pbi)₂Ir(acac) doped PVK system showed a high power efficiency of 3.84 lm/W and a luminance of 26,006 cd/m². The results indicated that both energy transfer and charge trapping have a significant influence on the performance of PLEDs. The devices have a broadened EL spectrum of full-width at half-maximum (FWHM) more than 100 nm, which can be realized for WOLEDs.     

NPB:CBP复合空穴传输层对黄色有机电致发光器件的影响

采用N, N'-diphenyl-N, N'-bis(1-naphthyl-pheny1)-1, 1'-biphenyl-4, 4'-diamine (NPB):4, 4'-N, N'-dicarbazole-biphenyl (CBP) 掺杂体系为复合空穴传输层,制备了结构为indium-tin oxide (ITO)/NPB:CBP/CBP:bis iridium (acetylacetonate) /2, 9-dimethyl-4, 7-diphenyl-p 关键词： 有机电致发光器件(OLEDs) 复合空穴传输层 NPB:CBP 器件性能     

Improved performance of InGaN light-emitting diodes with a novel sawtooth-shaped electron blocking layer

A sawtooth-shaped electron blocking layer is proposed to improve the performance of light-emitting diodes （LEDs）. The energy band diagram, the electrostatic field in the quantum well, the carrier concentration, the electron leakage, and the internal quantum efficiency are systematically studied. The simulation results show that the LED with a sawtooth-shaped electron blocking layer possesses higher output power and a smaller efficiency droop than the LED with a conventional A1GaN electron blocking layer, which is because the electron confinement is enhanced and the hole injection efficiency is improved by the appropriately modified electron blocking layer energy band.     

聚合物掺杂有机小分子发光二极管的电致发光与杂质陷阱效应

在新型空穴传输聚合物聚TPD(PTPD)中掺杂电子传输有机小分子荧光染料Rubrene制成薄膜器件.考察了不同掺杂浓度以及不同薄膜厚度器件的电致发光性能,结果表明存在杂质陷阱效应.基于固体中双注入理论，假设杂质陷阱限制在分立能级上，通过求解泊松方程，得到了掺杂器件J-V特性解析模型.该模型的计算值与实验结果一致.     

Effect of ZnO film thickness on the performance of organic light emitting diodes

The electrical and optical properties of the ZnO layers and of the ITO/ZnO bilayers are investigated. We show that a ZnO layer of about 120 nm is the best compromise to obtain simultaneously a high transmittance and conductivity. Moreover an X-ray diffraction analysis underscores that an amorphous ITO deposited on a polycrystalline ZnO could change into a polycrystalline ITO. The modifications of the ITO layer by a preliminary deposition of a 120 nm thick ZnO underlayer enables us to decrease the threshold voltage of organic light emitting diodes.     

Tandem organic light-emitting diode with a molybdenum tri-oxide thin film interconnector layer

A 10-nm-thick molybdenum tri-oxide(MoO3) thin film was used as the interconnector layer in tandem organic lightemitting devices(OLEDs).The tandem OLEDs with two identical emissive units consisting of N,N-bis(naphthalen-1-yl)N,N-bis(phenyl)-benzidine(NPB) /tris(8-hydroxyquinoline) aluminum(Alq3) exhibited current efficiency-current density characteristics superior to the conventional single-unit devices.At 20 mA/cm2,the current efficiency of the tandem OLEDs using the interconnector layers of MoO3 thin film was about 4.0 cd/A,which is about twice that of the corresponding conventional single-unit device(1.8cd/A).The tandem OLED showed a higher power efficiency than the conventional single-unit device for luminance over 1200cd/m2.The experimental results demonstrated that a MoO3 thin film with a proper thickness can be used as an effective interconnector layer in tandem OLEDs.Such an interconnector layer can be easily fabricated by simple thermal evaporation,greatly simplifying the device processing and fabrication processes required by previously reported interconnector layers.A possible explanation was proposed for the carrier generation of the MoO3 interconnector layer.     

Improved performances in top-emitting organic light-emitting diodes based on a semiconductor zinc oxide buffer layer

Electroluminescence performances are improved by inserting a semiconductor zinc oxide (ZnO) buffer layer into the emissive tris-(8-hydroxyquinoline)aluminum (Alq₃) layer and the semitransparent Al/Ag cathode in top-emitting organic light-emitting diodes (TEOLEDs) with structures of Si/SiO₂/Ag/Ag₂O/4,4′, 4″-tris(3- methylphenylphenylamino)triphenylamine/ 4,4′-bis[N-(1-naphthyl-1-)-N-phenyl- amino]-biphenyl/Alq₃/ZnO/Al/Ag. The thermal deposition of ZnO layer onto Alq₃ results in Alq₃ anion formation, which is beneficial to electron injection by generating some new energy levels in the forbidden band of Alq₃. In addition, a large hole-injection barrier of 2 eV at the interface of Alq₃/ZnO effectively blocks hole injection into Al/Ag cathode, leading to more carrier recombination in the emissive region.     

反对称n-AlGaN层对GaN基双蓝光波长发光二极管性能的影响

采用数值分析方法对在InGaN/GaN混合多量子阱活性层和n-GaN之间引入n-AlGaN层的GaN基双蓝光波长发光二极管进行模拟分析.结果发现,与传统的具有p-AlGaN电子阻挡层的双蓝光波长发光二极管相比,这种反对称n-AlGaN层能有效改善电子和空穴在混合多量子阱活性层中的分布均匀性及减少电子溢出,实现电子空穴在各个量子阱中的平衡辐射,从而减弱了双蓝光波长发光二极管的效率衰减.此外,通过改变Al组分可以提高双蓝光波长发光二极管发射光谱的稳定性:当Al组分为0.16时,双蓝光波长发光二极管的光谱在小电流下比较稳定,而Al组分为0.12时,光谱在大电流下比较稳定.