Evaluation of polarization field in InGaN/GaN multiple quantum well structures by using electroluminescence spectra shift

In order to investigate the inherent polarization intensity in InGaN/GaN multiple quantum well(MQW) structures,the electroluminescence(EL) spectra of three samples with different GaN barrier thicknesses of 21.3 nm, 11.4 nm, and 6.5 nm are experimentally studied. All of the EL spectra present a similar blue-shift under the low-level current injection,and then turns to a red-shift tendency when the current increases to a specific value, which is defined as the turning point.The value of this turning point differs from one another for the three InGaN/GaN MQW samples. Sample A, which has the GaN barrier thickness of 21.3 nm, shows the highest current injection level at the turning point as well as the largest value of blue-shift. It indicates that sample A has the maximum intensity of the polarization field. The red-shift of the EL spectra results from the vertical electron leakage in InGaN/GaN MQWs and the corresponding self-heating effect under the high-level current injection. As a result, it is an effective approach to evaluate the polarization field in the InGaN/GaN MQW structures by using the injection current level at the turning point and the blue-shift of the EL spectra profiles.

Study of Electroplex Emission from Organic Electroluminescent Devices with Rare Earth Complex

A novel organic electroluminescent device was made with the structure of ITO/PVK：Tb0.5Eu0.5（TTA）3 Dipy/ BCP/Alq3/Al（a） which utilized the rare earth complex Tb0.5Eu0.5（TTA）3 Dipy as the emitting layer. When it was driven under a direct electric field, 612 nm emission from EU^3＋ and 410 nm emission from PVK were observed. In addition, in the EL spectrum a new peak at 490 nm appeared. From the analysis of different devices, the mechanism of the new emission was studied. It was concluded that the new emission was the electroplex originating from the interface between the ligand （TTA）3Dipy and BCP.

Electroluminescent Excitation Mechanism of Erbium－activated Zinc Sulfide Semiconductor Thin Film Devices

The electroluminescunce (EL) transient characteristics of erbium-doped zinc sulfide thin film (TF) devices excited by short rectangular pulses are studied, the luminescence delay after de-exciting and the relaxation luminance peaks during decay are observed. A model description for energy transfer has been proposed. The experimental results can be theoretically explained with the computer curve fittings.

Red Electroluminescence and Photoluminescence from Novel Binuclear Europium Complex with Squaric Acid Ligand

A novel binuclear europium P-diketone complex with squaric acid ligand was synthesized for the first time. Its structure was elucidated by IR, UV, and Elemental Analysis. Red light emitting diode (LED) was fabricated by using the novel europium complex as an emitting layer, tris(8-quinolinolate) aluminum (III) (Alq(3)) as an electron-transporting layer, N, N'-diphenyl-N, N'-(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) as a hole-transporting layer. A cell structure of indium-tin-oxide/TPD/Eu-complex/Alq(3)/Mg: Ag was employed. Red electroluminescence was observed at room temperature with dc bias voltage of 2 V in this cell. 2 Red emission peaks at about 613 nm with maximum luminance of over 106 cd/m(2). Compared with the EL luminance from those europium complexes reported before, one from the Eu-complex is best in the same cells.

Rectification and electroluminescence of nanostructured GaN/Si heterojunction based on silicon nanoporous pillar array

A GaN/Si nanoheterojunction is prepared through growing Ga N nanocrystallites（nc-GaN） on a silicon nanoporous pillar array（Si-NPA） by a chemical vapor deposition（CVD） technique at a relatively low temperature. The average size of nc-Ga N is determined to be ~10 nm. The spectral measurements disclose that the photoluminescence（PL） from GaN/SiNPA is composed of an ultraviolet（UV） band and a broad band spanned from UV to red region, with the feature that the latter band is similar to that of electroluminescence（EL）. The electron transition from the energy levels of conduction band and, or, shallow donors to that of deep acceptors of Ga N is indicated to be responsible for both the broad-band PL and the EL luminescence. A study of the I-V characteristic shows that at a low forward bias, the current across the heterojunction is contact-limited while at a high forward bias it is bulk-limited, which follows the thermionic emission model and space-charge-limited current（SCLC） model, respectively. The bandgap offset analysis indicates that the carrier transport is dominated by electron injection from n-GaN into the p-Si-NPA, and the EL starts to appear only when holes begin to be injected from Si-NPA into GaN with biases higher than a threshold voltage.

Effect of Substrate Temperature on Electroluminescence of SrS∶HoF_3 Thin Film

The SrS∶HoF 3 Electroluminescent (EL) thin films are prepared at the different substrate temperature by electron beam evaporation. The crystallinity and EL characteristics of the samples are analyzed. It is found that the main diffraction peak is (200) at the higher substrate temperature and the main diffraction peak is (111) at the lower substrate temperature. The blue emission intensity and EL brightness of the SrS∶HoF 3 thin films increase with the increase of the substrate temperature. Annealing the samples can change the cyrstal phase and strengthen the blue emission of EL thin film.

Electroluminescence Gray Scale Display Driving Method and Circuit

The increasing use of color terminals for personal computers has raised a demand for video graphic adapter(VGA)-format panel displays. Since only monochrome(ZnS∶Mn) electroluminescence(EL) displays of suitable size and speed are available, lack of colors has to be replaced by grayscale in the first place. There are two basic driving methods to achieve grayscale in thin-film EL displays: pulse amplitude modulation(PAM) method and pulse width modulation(PWM) method. But there are serious disadvantages of the two traditional methods. For the former method, the high voltage PAM ICs are too expensive to produce the grayscale EL display in bulks and the driver integrated circuit(IC) is complex. Though the PWM method has good grayscale display quality, the hardware implementation is too complex. A new driving method with which the width and the amplitude of the pulse can be modulated and simultaneously the challenge can be solved efficaciously is presented.

太阳能电池板缺陷EL检测系统的设计

针对太阳能电池板或组件在生产的过程中会出现隐裂、碎片、崩边、虚焊、断栅等缺陷,介绍了一种应用电致发光原理和红外成像特性的缺陷检测系统。它应用电致发光理论,利用近红外成像检测方法,设计用于屏蔽可见光的暗箱,在暗箱中通过CCD近红外相机获取接入恒定直流源的太阳能电池板图像,通过计算机图像处理,得到完整、清晰的缺陷检测图像。

几种稠环芳烃有机EL材料性能的量子化学理论研究

采用量子化学半经验方法（ＲＨＦ／ＰＭ３）对几种稠环芳烃化合物电致发光（ＥＬ）材料的性质进行了理论研究。利用能量梯度法优化构型，对各优化的构型作振动分析，均未出现虚频率。在此基础上，采用ＲＨＦ／ＣＩＳ方法计算其电子光谱。并给出了化合物ＥＬ１，ＥＬ２电子光谱的最大波长λ与ＣＩＳ组态之间的关系。所有计算结果与实验值基本吻合。

聚合物/碳量子点复合EL器件及光谱移动机理

制备了结构为ITO/PEDOT∶PSS/polyvinylcarbazole（PVK）/carbon quantum dots（CDs）/LiF/Al的电致发光器件。器件的发光光谱显示：在电压从7 V增大到13 V的过程中,光谱峰值从380 nm移动到520 nm,色坐标由（0.20,0.20）移动到（0.29,0.35）。经与PL光谱对比认为,EL光谱包含了PVK与碳量子点的双重贡献,随着电压的增大,碳量子点的发射逐渐增强,PVK发光先增强后减弱。结合器件能级结构讨论了器件的发光机制,认为低电场下的PVK兼具发光层和电子阻挡层的功能,EL光谱为PVK层和碳量子点的发光叠加;随着电场强度的增大,碳量子点和PVK界面区的空间电荷阻止了电子向PVK的传输,光谱转变为由碳量子点和激基复合物的共同贡献。

Effects of ultrasonic bonding parameters on reliability of flip chip GaN-based light emitting diode

This work applied the ultrasonic bonding to package flip chip GaN-based light emitting diodes （flip chip LEDs） on Si substrates. The effects of ultrasonic bonding parameters on the reliability of flip chip GaN-based LED were investigated. In the sequent aging tests, samples were driven with a constant current of 80 mA for hundreds hours at the room temperature. It was found that the electroluminescence （EL） intensity variation had a large correlation to the ultrasonic power, and then to the bonding temperature and force. A high bonding temperature and ultrasonic power and a proper bonding force improved the EL intensity significantly. It was contributed to a strong atom inter-diffusion forming a stable joint at the bonding interface, The temperature fluctuation in the aging test was the main factor to generate a high inner stress forming delamination at the interface between the chip and Au bump. As a result, delamination had retarded the photons to emit out of the LED packaging and decay its EL intensity.

Study on Microcavity Organic Light-emitting Devices Containing Negative Refractive Index Dielectric Layer

A new structure containing negative refractive index dielectric layer（NRlDL） is introduced into microcavity. The properties of the new mierocavity organic light-emitting devices（MOLEDs） are investigated. In the experiment, the transfer matrix method is adopted. The dependence of reflectance and transmittance on the refractive index and thickness of NRIDL are analyzed in detail. Compared with the electroluminescence spectra of non-NRIDL diodes, the line widths of the spectra of the MOLEDs are narrower and all the peaks enhance. The results show that the new structure is beneficial to improve the performance and reduce the thickness of microcavity devices.

新型介质制成的粉末ACEL器件的主要光电特性

新型材料（Ｐ＿（１９９－５３５）、Ｐ＿（２１０－７７０））具有无色透明、粘性大、耐热、抗水性能强、介电常数大、电导小等优点，用它作为粉末交流电致发光的介质，制备粉末ＡＣＥＬ器件，并测试了这种器件的Ｌ－Ｖ、Ｉ－Ｖ、Ｌ－ｆ、Ｉ－ｆ、光谱和老化等主要光电特性，证明器件的发光性能得到较大幅度的提高．

基于DCGANs的半片光伏组件电致发光图像增强技术

针对半片光伏组件电致发光(electroluminescence,EL)缺陷自动识别过程中训练用样本不足导致模型过拟合的问题,采用深度卷积生成对抗网络(deep convolutional generative adversarial networks,DCGANs)生成可控制属性的半片光伏组件EL图像,再采用多尺度结构相似性(multiscale structural similarity,MS-SSIM)指标对生成的EL图像与拍摄的EL图像之间的相似程度进行了评估。评估结果得到,使用DCGANs生成的所有类型半片光伏组件的EL图像与拍摄的EL图像的MS-SSIM指标都大于0.55,大部分的MS-SSIM值在0.7附近。在分类模型的训练过程中,测试集准确率随着训练集中生成图像数量的增加而升高,当生成图像数量达到6 000张时,测试集准确率达到97.92%。实验结果表明,采用DCGANs能够生成高质量且可控制属性的半片光伏组件EL图像,较好地解决因缺少训练样本而导致的模型过拟合问题。

硅基多孔U-SiC薄膜的电致发光及其机理分析

单晶硅中注入高剂量的Ｃ＋ 离子，注入能量为５０ｋｅＶ，经高温退火后形成β－ＳｉＣ沉淀，再经电化学腐蚀形成多孔β－ＳｉＣ，样品表面蒸上一层半透明的金膜，在正向偏压高于２５Ｖ 时，可以获得波长约为４４７ｎｍ 的蓝光发射， 而且该蓝光发射随着电压的升高而增强．文中还将多孔β－ＳｉＣ薄膜的电致发光和其光致发光进行了比较。

有机金属螯合物电致发光材料的研究

有机电致发光平板显示被誉为“21世纪平板显示技术”,是当今平板显示研究的重点和热点。有机金属螯合物因其优良的电致发光性能,被首选为有机电致发光平板显示器的发光材料。针对近10年来有机金属螯合物电致发光材料及其器件的研究状况,对其分子种类、分子结构与发光性能的关系、分子设计准则、电致发光机制及其最新研究进展,进行了综述,展望了其发展趋势。

纳米ZnO光学性质研究进展

介绍了纳米ZnO常见发光谱的发光机制。在室温光致发光谱(PL)中,一般在380 nm处出现紫外发光,也有报道在357和377 nm处的紫外发光,列举了几种不同的发光解释。对于深能级发光,一般在400～550 nm出现连续的发光带,也有观察到深能级的声子伴线和声子复制现象。在低温光致发光谱的紫外发射中,一般观察到由自由激子发射(FX)、中性施主束缚激子发射(D0X)、施主-受主对跃迁峰(DAP)、中性施主束缚激子对应的双电子卫星峰(TES)以及声子伴线。综述了纳米ZnO的喇曼光谱、透射光谱、电致发光谱(EL)的特征,最后展望了纳米ZnO的光学性能研究前景。

GaN基白光LED的结温测量

用正向电压法、管脚法和蓝白比法等三种方法测量GaN基白光LED的结温,获得了较为准确的结温,误差可以控制在4℃以内。正向电压法在恒定电流的条件下,得到了正向电压与结温的线性关系;蓝白比法在不同环境温度和不同注入电流两种情况下,都得到了蓝白比与结温较好的线性关系。提出了蓝白比法可能的物理机制,提高环境温度和增大注入电流都会使结温升高,蓝光峰值波长也会改变,这两个因素都会影响荧光粉的激发和发光效率。降低结温需要考虑的主要因素有白光LED的接触电阻、串联电阻和外量子效率,封装材料的热导率,反射杯和管脚的设计,以及空气散热部分的散热面积等。

1,5-萘二胺衍生物的光谱分析及发光性能研究

合成了一种纯度较高的1,5-萘二胺衍生物(NPN),制备了NPN薄膜。利用紫外-可见吸收光谱和荧光发射光谱研究了NPN的发光行为,并结合电化学循环伏安法研究了其电子能级结构。结果表明,NPN的荧光光谱表现出明显的溶剂效应,认为其发生了从电子给体N原子到电子受体芳环之间的分子内电子转移,形成分子内电子转移络合物;从NPN薄膜与其溶液的吸收光谱峰值比较中看出吸收峰红移,认为薄膜中分子形成“J-聚集体”;NPN的HOMO能级为-5.74 eV,光学禁带为2.79 eV;在365 nm紫外光的激发下,产生发光峰在448.6 nm附近、谱线带宽为72.6 nm的蓝光发射,发光亮度高,色纯度高。

具有手性侧链的卟啉液晶化合物的合成和发光性能研究

通过在卟啉环上引入手性侧链的方法合成了两类 (4个 )卟啉液晶化合物 ,并用元素分析 ,UV vis,FT IR ,1HNMR ,MS ,DSC ,圆二色谱 (CD)和偏光显微镜对化合物的结构进行了表征 .研究结果表明 ,这些化合物具有液晶性质 ,固体荧光和电致发光性质 ,其中两个卟啉配体有较强的CD吸收性能 .