Transient and stable electroluminescence properties of alternating-current biased organic light-emitting diodes

In this work,transient electroluminescence (EL) (brightness-voltage waveform curve) was utilized to investigate the working mechanism of alternating-current biased organic light-emitting diodes (AC-OLE...     

Analysis of alternating current driven electroluminescence in organic light emitting diodes: A comparative study

The alternating current (AC) responses of double-injection and double-insulated organic light-emitting diodes (OLEDs) were investigated and compared. To reveal the electroluminescent (EL) processes in these devices, the AC voltage and frequency dependence of the EL intensity and capacitive current were studied in the time domain with a focus on phase difference analysis. It was found that the voltage-dependent transit time and frequency-dependent carrier distribution were important for the AC-driven performance of the double-injection OLEDs. In contrast, although the double-insulated OLEDs shared some similarities with the double-injection OLEDs, they had some unique characteristics, which were the absence of resistive current and phase shift of EL profiles. It was revealed that the EL in the double-insulated OLEDs was driven by the displacement current generated by the ionization of the doped layers, which, however, formed space charge regions and undermined the EL emission. The space charge redistributed the electric field across the devices after the initiation of EL, making the EL maintain for a limited time interval. This effect was significant under low frequency and high AC voltage. Comparing the phase difference between both devices, it was indicated that the space charge effect was responsible for the observed EL phase shift and the asymmetric EL profiles at low frequency and high AC voltage in the double-insulated OLEDs. The proposed model was also of help to understand the EL saturation phenomena with AC frequency and voltage in those devices.     

利用电致发光线的光学电压有效值传感器

利用电致发光(EL)线设计并实验研究了一种光学电压有效值传感器。所用EL线的主要材料为ZnS:Cu,在一定幅值的工频电压作用下,可产生中心波长约为525nm的可见光;将此EL用塑料光纤(POF)传输到光电探测器(PD),则PD的开路电压与被测电压有效值之间具有近似线性关系。对100～500V工频电压有效值进行了实验测量,其电压测量灵敏度约为10.8μV/V,非线性误差低于1.8%。实验测量了所用EL线的电致发光光谱、输入阻抗以及EL的温度特性。与以往基于Pockels电光效应的光学电压传感器不同的是,本文提出的电压传感器不需要工作光源,并具有结构简单、成本低等优点。     

柔性ACPEL显示器件的研究及应用

介绍了ＣＰＥＩ塑料基板为载体而制作的交流粉末电致发光显示器件（ＡＣＰＥＬ）。给出了亮度,效率,颜色与激发电压,频率之间的特性曲线,列出了器件的主要性能指标。     

交流粉末电致发光显示板及其应用

介绍了交流粉末电致发光显示板（EL）的结构和原理、发光强度与驱动信号的电压、频率之间的关系、老化机理,探讨了几种驱动方法,并给出了一应用于玩具的实例。     

利用光电导开关的光电子相关测量

本文在实验的基础上,提出了光电导开关等效时变电导的新表达式。据此分析了光电导开关在高速脉冲的产生和取样以及在光电子相关测量中的特性。分析的结果与实验基本一致,为将来利用光电子相关方法测量电子器件打下了基础。在实验中采用较为简单的工艺,获得光电导开关的上升时间为100ps。相信,只要增加离子轰击处理,上升时间可望达到10ps。     

ZnS∶Cu粉末交流电致发光器件特性研究

以商用ZnS∶Cu交流电致发光粉作为发光层,以ITO作为电极制作了粉末交流电致发光器件。以交流脉冲方波为驱动电压,详细研究了外加电压的幅值,频率以及脉宽对其发光频谱及亮度的影响。实验结果表明当电压小于200 V,发光亮度随着电压的升高而缓慢增强,当电压大于200 V,随着电压的升高亮度准线性增强。随着驱动频率的增大,发光光谱的中心波长发生蓝移,从100 Hz时的504 nm(绿光)到100 kHz时的450 nm(蓝光),发光亮度随频率增加先快速增强然后逐渐趋于饱和,达到一个极值后开始减小。随着脉宽的增大,发光亮度线性增强。另外文章中对驱动频率影响发光光谱的原因进行了深入分析,这对进一步研究ZnS∶Cu交流电致发光粉的发光机理有着重要的作用。     

Bifunctional organic materials for OLEDs based on Tröger’s base: Subtle structural changes and significant differences in electroluminescence

Three bifunctional organic materials based on Tröger’s base (TB) scaffold have been designed, synthesized and their functional utility in OLEDs demonstrated through fabrication of devices. The diarylamino-functionalized TBs, i.e., A-TB, PA-TB and P-TB, are all amorphous with considerably high T_gs and permit modulation of electroluminescence with variation of one of the N-aryl rings, e.g., anthryl to 10-phenylanthryl to pyrenyl. Subtle structural modifications are found to manifest in rare pure yellow EL emission from PA-TB.     

Efficient iridium(III) based, true-blue emitting phosphorescent OLEDS employing both double emission and double buffer layers

New device architectures and efficient iridium based phosphors were simultaneously developed for fabrication of true-blue phosphorescent organic light-emitting devices (OLEDs). To fully explore the potential of these true-blue-emitting phosphors, we employed a device architecture that incorporates both double-emitting layers (one with hole-transport and the second with electron-transport materials) and double buffer layers for efficient exciton confinement. In addition, the parent, true-blue emitting heteroleptic Ir^III complex Ir1 was synthesized by incorporating one 4,6-difluorophenyl-2-pyridyl cyclometalate (dfppy) together with two 3-(trifluoromethyl)-5-pyridyl pyrazolates (fppz), while others derivatives Ir2–Ir4 were prepared by addition of alkyl substituent at the pyridyl sites. Electrophosphorescence with efficiencies up to 13.7% photon/electron and 20.4 cd/A, and with adequate CIE_x,y color coordinates of (0.157, 0.189) were successfully achieved.     

LiF作电子注入缓冲层对有机电致发光器件电容的影响

已经有多种方法分析了LiF作为电子注入缓冲层对有机电致发光器件的影响,用LiF/Al双层阴极和发光层Alq3制成的有机电致发光器件(OLED),可以降低器件的开启电压,提高器件的发光效率、发光亮度。文章主要对OLEDs(A):Al/Alq3/ITO和(B):Al/LiF(1nm)/Alq3/ITO的C-V特性进行了研究,当在阴极和发光层Alq3之间加上1nm厚的LiF层作为电子注入缓冲层以后,器件的电容由不加LiF时的72500pF减小到12500pF,由于电容的减小,有效地降低了器件的功耗,进而提高了器件的寿命,节约了能源,进一步改善了器件的性能。     

交流无声放电暂态过程的理论分析

根据交流无声放电机理的物理模型,提出分析其暂态过程的数学模型。然后由其解析解计算这种无声放电的着火特性和放电电流密度对时间的依赖关系,并与实验结果相比较。最后简要地讨论了计算结果与实验结果间的差距。     

Development of Fiber Optically Driven Instrument for High—voltage Line Current

The measurement theorem of fiber optically driven instrument for high-voltage line current is presented.The PLL voltage-frequency-narrow pulse principle and its micro-consuption mechanism are proposed.followed by anayssis on the two main factors affecting PLL measurement precision.A software desighn scheme using 80C196KB mciro-controller is introduced.The experiment results is satisfactory.     

VGA信号分配及远程传输系统

介绍了基于电压跟随的视频VGA信号分配的原理以及实际电路的设计,以实现视频信号本地的多路显示。视频信号在实现远程传输时,需对视频信号进行放大,增大信号的驱动能力。为此,介绍了基于EL4543差分放大的视频信号远程传输发送端电路及其工作原理;在远程接收端,通过EL9111差分接收和EL9115的模拟补偿,恢复视频信号。采用本设计的视频传输距离可达200m左右。     

Application of Green's functions for analysis of transient thermal states in electronic circuits

This paper presents an approach to the modelling of transient thermal states in electronic circuits using an analytical solution of the heat equation. Fully three-dimensional analytical time dependent solutions are determined with the help of Green's functions. The solution method is illustrated in detail on a practical example, where the results of transient thermal simulations of a real hybrid circuit are compared with infrared measurements.     

EL场致显示技术及其在便携式电子系统中的应用

介绍了EL场致显示技术及如何构建EL显示控制模块以便对EL屏进行显示控制的原理和方法,给出了控制模块的设计框图及实际的电路连接图。最后给出了该接口技术的软件设计流程图和初始化程序。     

交流电能表在计量检定中的常见故障及处理方法

交流电能表是计量电能的主要工具,其计量检定的精准度直接关系着电能表的后期使用,以及用户和电力企业之间的利益关系.然而,交流电能表在计量检定当中的一些常见故障,严重影响了交流电表的使用.本文在介绍交流电能表种类的基础上,就不同类型交流电能表的计量检定故障及处理方法进行了探究.     

Efficient hole-transporter for phosphorescent organic light emitting diodes with a simple molecular structure

N,N-diphenyl-4-(quinolin-8-yl)aniline (SQTPA), which composes a triphenylamine group and a quinoline group, has been synthesized and employed as a hole-transporter in phosphorescent OLEDs. It has been proved that SQTPA has efficient hole-transport property with a hole-mobility of 3.60 × 10⁻⁵ cm²/V s at the electric field of 800 (V/cm)^1/2, which is higher than that of NPB (1.93 × 10⁻⁵ cm²/V s). Blue, orange and green phosphorescent OLEDs have been fabricated based on FIrpic, Ir(2-phq)₃, Ir(ppy)₃ with typical structures by using SQTPA as the hole-transporter. The SQTPA-based devices show maximum external quantum efficiencies and power efficiencies of 17.5%, 32.5 lm/W for blue, 12.3%, 20.5 lm/W for orange and 20.3%, 64.5 lm/W for green. The performances of SQTPA-based devices are much better than that of NPB-based phosphorescent OLEDs with similar structures. Thought of its very simple molecular structure and easy synthetic route, SQTPA should be an efficient hole-transporter for phosphorescent OLEDs.