新型全方位反射铝镓铟磷薄膜发光二极管

提出了一种新型全方位反射铝镓铟磷(AlGaInP)薄膜发光二极管(LED)的结构和制作工艺，在这个结构里应用了低折射率的介质和高反射率的金属联合作为反光镜.用金锡合金(80Au20Sn，重量比)作为焊料把带有反光镜的AlGaInP LED外延片倒装键合到GaAs基板上(RS-LED)，去掉外延片GaAs衬底，把被GaAS衬底吸收的光反射出去.通过与常规AlGaInP 吸收衬底LEDs(AS-LED)和带有DBR的AlGaInP 吸收衬底LEDs(AS-LED(DBR))电、光特性的比较，证明新型全方位反射AlGaInP薄膜LED结构能极大提高亮度和效率.正向电流20mA时，RS-LED的光输出功率和流明效率分别是AS-LED的3.2倍和2.2倍，是AS-LED(DBR)的2倍和1.5倍.RS-LED(20mA下峰值波长627nm)的轴向光强达到194.3mcd，是AS-LED(20mA下峰值波长624nm)轴向光强的2.8倍，是AS-LED(DBR)(20mA下峰值波长623nm)轴向光强的1.6倍. 关键词： 铝镓铟磷 薄膜发光管 全方位反射镜 发光强度     

ITO界面调制层对GZO电极LED器件性能的影响

采用磁控溅射制备GZO和具有ITO界面调控层的GZO(ITO/GZO)透明导电薄膜作为大功率LED的电流扩散层,对比研究界面调控层对LED器件性能的影响。研究结果表明,ITO/GZO薄膜的透过率在可见光区达80%以上,退火后的ITO/GZO薄膜有较低的电阻率(1.15×10^-3 Ω·cm)。ITO调控层的介入能够调制GZO表面粗糙度,有利于改善LED外量子效率,降低GZO/p-GaN界面的接触势垒,提高LED器件的光电性 能。通过ITO界面调控后,LED器件20 mA驱动电流下的工作电压从9.5 V降低为6.8 V,发光强度从245 mcd 升到297 mcd,提高了20%;驱动电流为35 mA时,其发光强度从340.5 mcd 升到511 mcd,提高了50%。     

Improvement of the light output and contact resistance of InGaN-based light-emitting diodes based on tantalum-doped indium tin oxide as p-type electrodes

This paper reports that highly transparent and low resistance tantalum-doped indium tin oxide (Ta-doped ITO) films contacted to p-type GaN have been prepared by the electron-beam evaporation technique. The Ta-doped ITO contacts become Ohmic with a specific contact resistance of $\sim 5.65\times 10^{ - 5}$~$\Omega \cdot$cm$^{2}$ and show the transmittance of $\sim $98% at a wavelength of 440~nm when annealed at 500~\du. Blue light emitting diodes (LEDs) fabricated with Ta-doped ITO p-type Ohmic contact layers give a forward-bias voltage of 3.21~V at an injection current of 20~mA. It further shows that the output power of LEDs with Ta-doped ITO contacts is enhanced 62% at 20~mA in comparison with that of LEDs with conventional Ni/Au contacts.     

Numerical simulation of ultra-thin CdTe solar cells with a buffer layer of MoOx in the backwall configuration

The software of Solar Cell Capacitance Simulator (SCAPS) is used to investigate the performance of ultra-thin CdTe solar cells in the backwall configuration (glass/ITO/MoO_x/CdTe/CdS/SnO₂/Ag). The backwall structure utilizes ultra-thin CdTe absorber layer instead of CdS film facing light illumination, which eliminates the absorption of CdS in short-wavelength region and improves the blue response of CdTe. A buffer layer of MoO_x is added to modify the contact between CdTe and ITO, reducing the valence band barrier height and simultaneously forming an electron reflector, which can reduce electron-hole recombination at this contact. When the thickness of MoO_x is 2 nm, the simulation results show that an efficiency can reach up to 25.5% with high ITO work function and ideal interface recombination velocity.     

4,4′,4″-三(N-3-甲基苯基-N-苯基氨基)三苯胺掺杂MoOx作为空穴传输层对有机太阳电池性能的影响

通过采用4,4′,4″-三(N-3-甲基苯基-N-苯基氨基)三苯胺 (m-MTDATA)掺入MoO_x作为器件的空穴传输层来提高酞菁铜(CuPc)/C₆₀小分子 有机太阳电池的效率. 采用真空蒸镀的方法制备了一系列器件, 其中结构为铟锡氧化物 (ITO)/m-MTDATA:MoO_x(3:1)(30 nm)/CuPc(20 nm)/C₆₀(40 nm)/4,7-二苯 基-1,10-菲罗啉 (Bphen)(8 nm)/LiF(0.8 nm)/Al(100 nm)的器件, 在AM1.5 (100 mW/cm²)模拟太阳光的照射条件下, 开路电压V_oc=0.40 V, 短路电流J_sc=6.59 mA/cm², 填充因子为0.55, 光电转换效率达1.46%, 比没有空穴传输层的器件ITO/CuPc(20 nm)/C₆₀(40 nm)/Bphen(8 nm)/LiF(0.8 nm)/Al(100 nm) 光电转换效率提高了38%. 研究表明, 加入m-MTDATA:MoO_x(3:1)(30 nm)空穴传输层减小了有机层和ITO电极之间的接触电阻, 从而减小了整个器件的串联电阻, 提高了器件的光电转换效率.     

GaN-based light-emitting diode with ZnO nanotexture layer prepared using hydrogen gas

ZnO films were deposited on indium tin oxide (ITO), which formed the transparent conductive layer (TCL) of a GaN-based light-emitting diode (LED), by ultrasonic spraying pyrolysis to increase the light output power. The ZnO nanotexture was formed by treating the as-deposited ZnO films with hydrogen. The root mean square (RMS) roughness increased from 4.47 to 7.89 nm before hydrogen treatment to 10.82-15.81 nm after hydrogen treatment for 20 min. Typical current-voltage (I-V) characteristics of the GaN-based LEDs with a ZnO nanotexture layer have a forward-bias voltage of 3.25 V at an injection current of 20 mA. The light output power of a GaN-based LED with a ZnO nanotexture layer improved to as much as about 27.5% at a forward current of 20 mA.     

利用单层密排的纳米球提高发光二极管的出光效率

在发光二极管(LED)的透明电极层上制作单层六角密排的聚苯乙烯(polystyrene, PS) 纳米球, 研究提高GaN基蓝光LED的出光效率. 采用自组装的方法在透明电极铟锡氧化物层上制备了直径分别约为250, 300, 450, 600和950 nm的PS纳米球, 并且开展了电致发光的研究. 结果表明, 在LED的透明电极层上附有PS纳米球能有效地提高LED的出光效率; 当PS纳米球的直径与出射光的波长比较接近时, LED的出光效率最优. 与参考样品相比, 在20 mA和150 mA工作电流下, 附有PS纳米球的样品的发光效率分别增加1.34倍和1.25倍. 三维时域有限差分方法计算表明, 该出光增强主要归因于附有PS纳米球的LED结构可以增大LED结构的光输出临界角, 从而提高LED的出光效率. 因此, 这是一种低成本的实现高效率LED的方法.     

Impact of an indium oxide/indium-tin oxide mixed structure for GaN-based light-emitting diodes

An interesting GaN-based light emitting diode (LED) using a 50 nm indium oxide (In₂O₃)/250 nm indium-tin oxide (ITO) mixed structure to replace the commonly used ITO (250 nm) current spreading layer is fabricated and studied. Use of the In₂O₃ layer could reduce the contact resistance of p-GaN in LEDs. In addition, this highly-resistive In₂O₃ layer, below the ITO layer could improve the current spreading performance. Experimentally, at room temperature, using this mixed structure, the luminous and EL intensities are enhanced by 17.7 and 17.1%, respectively.     

Improvement of GaN light-emitting diodes with surface-treated Al-doped ZnO transparent Ohmic contacts by holographic photonic crystal

This letter presents a holographic photonic crystal (H-PhC) Al-doped ZnO (AZO) transparent Ohmic contact layer on p-GaN to increase the light output of GaN-based LEDs without destroying the p-GaN. The operating voltage of the PhC LEDs at 20 mA was almost the same as that of the typical planar AZO LEDs. While the resultant PhC LED devices exhibited significant improvements in light extraction, up to 1.22 times that of planar AZO LEDs without PhC integration. Temperature dependence of the integrated photoluminescence intensity indicates that this improvement can be attributed to the increased extraction efficiency due to the surface modification. These results demonstrate that the surface-treated AZO layer by H-PhCs is suitable for fabricating high-brightness GaN-based LEDs.     

高效率的有机电致发光器件

有机电致发光器件 (OL EDs)的发光机理包括电子和空穴从电极的注入、激子的形成及复合发光 ,其中 ,空穴和电子的注入平衡是非常重要的。为了平衡载流子的注入以得到高效率和稳定性好的器件 ,人们不仅使用了电子注入更为有效的 L i F/ Al[1] 和 Cs F/ Al[2 ] 等复合电极 ,同时也使用了空穴缓冲层 ,如 S.A.Van Slyke等 [3]在ITO和 NPB之间使用 Cu Pc,使得器件的稳定性得到了明显的提高 ;A.Gyoutoku等[4 ] 用碳膜使器件的半寿命超过 3 5 0 0小时 ;最近 ,Y.Kurosaka等 [5]和 Z.B.Deng[6 ]分别在 ITO和空穴传输层之间插入一薄层 Al…     

Use of graphene for forming Al-based p-type reflectors for near ultraviolet InGaN/AlGaN-based light-emitting diode

We demonstrated the improved performance of near UV (365 nm) InGaN/AlGaN-based LEDs using highly reflective Al-based p-type reflectors with graphene sheets as a diffusion barrier. The use of graphene sheets did not degrade the reflectance of ITO/Al contacts, viz. ∼81% at 365 nm. The ITO/graphene/Al contacts annealed at 300 °C exhibited better ohmic behavior with a specific contact resistance of 1.5 × 10⁻³ Ωcm² than the ITO/Al contact (with 9.5 × 10⁻³ Ωcm²). Near UV LEDs fabricated with the ITO/graphene/Al contact annealed at 300 °C showed a 7.2% higher light output (at 0.1 W) than LEDs with the ITO/Al reflector annealed at 300 °C. The SIMS results exhibited that, unlike the ITO/graphene/Al, the ITO/Al contacts undergo a significant indiffusion of Al atoms toward the GaN after annealing. Furthermore, both Ga and Mg atoms were also more extensively outdiffused in the ITO/Al contacts after annealing. On the basis of the SIMS and electrical results, the possible explanations for the annealing-induced degradation of the ITO/Al contacts are described and discussed.     

Effect of tin-doped indium oxide film as capping layer on the agglomeration of copper film and the appearance of copper silicide

In this work, the effect of tin-doped indium oxide (ITO) film as capping layer on the agglomeration of copper film and the appearance of copper silicide was studied. Both samples of Cu 100 nm/ITO 10 nm/Si and ITO 20 nm/Cu 100 nm/ITO 10 nm/Si were prepared by sputtering deposition. After annealing in a rapid thermal annealing (RTA) furnace at various temperatures for 5 min in vacuum, the samples were characterized by four probe measurement for sheet resistance, X-ray diffraction (XRD) analysis for phase identification, scanning electron microscopy (SEM) for surface morphology and transmission electron microscopy (TEM) for microstructure.The results show that the sample with ITO capping layer is a good diffusion barrier between copper and silicon at least up to 750 °C, which is 100 °C higher than that of the sample without ITO capping layer. The failure temperature of the sample with ITO capping layer is about 800 °C, which is 100 °C higher than that of the sample without ITO capping layer. The ITO capping layer on Cu/ITO/Si can obstacle the agglomeration of copper film and the appearance of Cu₃Si phase.     

Color tunable high efficiency microcavity organic light-emitting diodes

Color tunable microcavity organic light-emitting diodes (OLEDs) with structure of distributed Bragg reflectors (DBR)/indium-tin-oxide (ITO)/N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB)/tris(8-hydroxyquinoline) aluminum (Alq₃)/LiF/Al were fabricated. Orange red and green light emissions with full width at half maximum (FWHM) of less than 20 nm were obtained through simply changing the thickness of NPB layer. Furthermore, due to the effective modification of the spontaneous emission within microcavity, the brightness and electroluminescent (EL) efficiency of the microcavity OLEDs were significantly enhanced. The maximum brightness and current efficiency, respectively, reached 31000 cd/m² at a current density of 480.0 mA/cm² and 8.3 cd/A at a current density of 110.0 mA/cm² for green devices, and 9700 cd/m² at a current density of 180.0 mA/cm² and 6.6 cd/A at a current density of 36.4 mA/cm² for red devices, which are over 1.5 times higher than those of noncavity OLEDs.      

Fabrication and characterization of Pt intermediate transparent and conducting ITO/Pt/ITO multilayer films

Platinum intermediate transparent and conducting ITO/metal/ITO (IMI) multilayered films were deposited by RF and DC magnetron sputtering on polycarbonate substrates without intentional substrate heating. Changes in the microstructure and optoelectrical properties of the films were investigated with respect to the thickness of the intermediate Pt layer in the IMI films. The thickness of Pt film was varied from 5 to 20 nm.In XRD measurements, neither ITO single-layer films nor IMI multilayer films showed any characteristic diffraction peaks for In₂O₃ or SnO₂. Only a weak diffraction peak for Pt (1 1 1) was obtained in the XRD spectra. Thus, it can be concluded that the Pt-intermediated films in the IMI films did not affect the crystallinity of the ITO films. However, equivalent resistivity was dependent on the presence and thickness of the Pt-intermediated layer. It decreased as low as 3.3×10⁻⁴ Ω cm for ITO 50 nm/Pt 20 nm/ITO 30 nm films. Optical transmittance was also strongly influenced by the Pt-intermediated layer. As Pt thickness in the IMI films increased, optical transmittance decreased to as low as 30% for ITO 50 nm/Pt 20 nm/ITO 30 nm films.     

基于金属掺杂ITO透明导电层的紫外LED制备

为降低ITO薄膜对紫外波段的光吸收,制备低电压高功率的紫外LED,研究了一种基于金属掺杂ITO透明导电层的365 nm紫外LED的制备工艺。利用1 cm厚的石英片生长了不同厚度ITO薄膜以及在ITO上掺杂不同金属的新型薄膜,并研究了在不同的退火条件下这种薄膜的电阻和透过率,分析了掺杂金属ITO薄膜的带隙变化。将这种掺杂的ITO薄膜生长在365 nm外延片上并完成电极生长,制备成14 mil×28 mil的正装LED芯片。利用电致发光（EL）设备对LED光电性能进行测试并对比。实验结果表明:掺Al金属的ITO薄膜能够相对ITO薄膜的带隙提高0.15 eV。在600℃退火后,方块电阻降低6.2 Ω/□,透过率在356 nm处达到90.8%。在120 mA注入电流下,365 nm LED的电压降低0.3 V,功率提高14.7%。ITO薄膜掺金属能够影响薄膜带隙,改变紫光LED光电性能。     

掺杂聚合物蓝光发光二极管

报道了用有机染料ＴＰＢ（１，ｌ，４，４－四苯基丁二烯）分散到ＰＶＫ（聚乙烯基咔唑）中的掺杂聚合物作有源层制作的蓝光发光二极管及其发光特性。聚合物发光层用旋转涂敷的方法制备，用透明导电材料ＩＴＯ（铟锡氧化物）、金属Ａｌ作为正负电极。器件正向偏压为１３Ｖ时，可以看到蓝光发射，峰值波长为４５５ｎｍ，注入电流为５０ｍＡ／ｃｍ２时，亮度为４４ｃｄ／ｍ２。     

利用微球层提高有机发光二极管出光效率

采用自组装的方法(提拉法)在普通玻璃盖玻片衬底上制备了聚苯乙烯微球层,对其进行简单的热处理可获得类似微透镜的结构。利用折射率匹配液将其耦合在常规OLEDs的出光面,研究了其对器件光学特性的影响。初步的研究结果表明:热处理后的直径为3μmPS微球层可将限制在玻璃衬底中的部分光耦合到前向外部空间,并将OLEDs器件正方向的发光亮度(效率)提高大约9%。     

Forming the graded-refractive-index antireflection layers on light-emitting diodes to enhance the light extraction

Distributed antireflection (AR) layers with different composition ratios of ITO and SiO(2) formed on an ITO electrode of GaN-based LEDs provide substantial enhancement in light-extraction efficiency. By using the coradio frequency magnetron sputtering deposition, four 50 nm thick AR layers with graduated refractive indices were fabricated. The effect of the AR layers on enhancing the efficiency of the LED device was analyzed by electroluminescence (EL) and I-V measurements. As a result, the EL intensity of the LED device grown on the patterned sapphire substrate with AR layers was increased by up to 13% compared to the conventional patterned sapphire substrate-applied LED device without AR layers at a drive current of 20 mA. The AR layers on top of the LED device gradually changed the refractive indices between ITO (n=2.1) and air (n=1.0), which minimized the total internal reflection of generated light. And no degradation in the electrical characteristic of the LEDs was observed according to the I-V measurements.     

RGB tricolor produced by white-based top-emitting organic light-emitting diodes with microcavity structure

RGB pixels by microcavity top-emitting organic light-emitting diode (TOLED) is beneficial to both minimizing the loss of light and improving the color purity and the efficiency. Based on the multi-emitting layers, white organic light-emitting diodes (OLEDs) and microcavity TOLEDs were prepared. TOLEDs were fabricated using Ag/ITO as the reflector and adjusting layer, Al/Ag as semi-transparent cathode, Alq:DCJTB/TBADN:TBPe/Alq:C545 as white light emitting layer. By adjusting the thickness of ITO, optical length of cavity and the color of the device have been changed. So we get RGB tricolor devices. The peak wavelengths are 476 nm, 539 nm, 601 nm, Commission Internationale d’Eclairage (CIE) coordinates are (0.133, 0.201), (0.335, 0.567), (0.513, 0.360), FWHM are 32 nm, 50 nm, 73 nm for blue, green and red, respectively.     

Highly efficient greenish blue-emitting organic diodes based on pyrene derivatives

We report the synthesis of pyrene derivatives as the light emissive layer for highly efficient organic electroluminescence (EL) diodes. Multilayer devices were fabricated with pyrene derivatives (ITO/NPB (50 nm)/blue material (30 nm)/BCP (10 nm)/Alq₃ (30 nm)/LiF (1 nm)/Al). By using 1,1′-dipyrene (DP) and 1,4-dipyrenyl benzene (DPB), the devices produced the blue EL emissions with 1931 Commission International de L’Eclairage coordinates of (x=0.21, y=0.35) and (x=0.19, y=0.25), respectively. The device with DPB shows a maximum brightness of 42,445 cd/m² at 400 mA/cm² and the luminance efficiency of 8.57 cd/A and 5.18 lm/W at 20 mA/cm².