一种LTPS-TFT AMOLED像素电路的理论研究

本文对一种LTPS-TFT AMOLED电压型阈值电压(V_(th))补偿像素电路进行了理论研究,分析了影响V_(th)补偿效果的主要因素。电路的补偿效果主要由驱动TFTV_(th)的获取精度和随后的保持精度决定。在V_(th)获取过程中,相关误差主要由驱动TFT转移特性电流对存储电容充电的充电率不足产生;在显示信号与V_(th)叠加过程中,与V_(th)保持节点连接的电容增量等因素会造成V_(th)保持精度的损失。根据分析的结果,本文解释了高分辨率像素电路补偿效果下降的原因。     

具有顶部发光结构的AMOLED交流驱动电路

A new voltage programmed pixel circuit with top emission design for active-matrix organic lightemitting diode(AMOLED) displays is presented and verified by HSPICE simulations.The proposed pixel circuit consists of five poly-Si TFTs,and can effectively compensate for the threshold voltage variation of the driving TFT.Meanwhile,the proposed pixel circuit offers an AC driving mode for the OLED by the two adjacent pulse voltage sources,which can suppress the degradation of the OLED.Moreover,a high contrast ratio can be achieved by the proposed pixel circuit since the OLED does not emit any light except for the emission period.     

Novel TFT-Based emission driver in high performance AMOLED display applications

A novel integrated row driver for emission control with n-type thin-film transistors (TFTs) was proposed. A single stage of the proposed driving circuit consists of charge supplement unit, improved inverter, and power conservation unit besides input TFT and driving TFTs. Simulations were carried out with fabricated LTPS TFT. The results show the driving circuit achieves leakage prevention with no floating state and high reliability even under the V_th shift of 3 V. What's more, further measurement results show a 3 μs pulse width can be generated by the circuit, supporting 8k4k resolution with high refresh rate of 120 Hz. And the capability of low refresh rate (1 Hz) driving also can be achieved without degradation. In addition, only three control signals (two non-overlap clocks and one input signal) are used in the proposed circuit, where input signal of present stage is connected with the output of its previous stage. That means the row driver can work under independent control and be not susceptible, which contributes to generating adjustable pulse width for pulse width modulation (PWM) in active matrix organic light-emitting diode (AMOLED) displays.     

基于低温多晶硅薄膜晶体管的AMOLED交流像素电路

This work presents a new voltage programmed pixel circuit for an active-matrix organic light-emitting diode(AMOLED) display.The proposed pixel circuit consists of six low temperature polycrystalline silicon thinfilm transistors(LTPS TFTs),one storage capacitor,and one OLED,and is verified by simulation work using HSPICE software.Besides effectively compensating for the threshold voltage variation of the driving TFT and OLED,the proposed pixel circuit offers an AC driving mode for the OLED,which can suppress the degradation of the OLED.Moreover,a high contrast ratio can be achieved by the proposed pixel circuit since the OLED does not emit any light except for the emission period.     

AMOLED控制电路中的双节拍处理模式

提出了一种面对高分辨率的有源有机发光二极管(AMOLED)矩阵屏,减少向OLED屏写数据所用时间的方案.在协调数据的写入和读取方式上,提出了一种双节拍模式的控制驱动方法,即外设RAM设立双套模式,两套RAM交替对数据进行读写操作,并且采用两组驱动芯片分奇偶列同时向屏写数据.通过对所设计的控制电路进行仿真以及实测结果对照,表明该设计能节省写过程,为显示赢得了更多的时间,比预先的设计增长了31%,有利达到良好显示的效果.     

有源OLED像素电路的设计与仿真

设计了有源OLED显示用非晶硅薄膜晶体管恒流型4-TFT像素驱动电路，并给出了驱动方法。应用HSPICE仿真了恒流型像素驱动电路的工作过程，详细分析了源（Source）电压VDD、存储电容Cs，以及开关晶体管T1、驱动晶体管T3的宽长比等参数对电路的输出特性的影响。仿真结果表明，此电路可以在整个帧周期持续供给OLED器件电流，并且解决了由于各像素驱动管阈值电压的差异带来的OLED亮度的不均匀问题。     

具有容错功能的OLED有源驱动电路

以有机电致发光器件(OLED)为基础的显示或照明器件,通常会受到短路故障的影响,从而使得像素失效,降低面板的亮度,进而严重地影响亮度的均匀性,并且会产生大量的功耗.本文介绍了一种新的有源OLED驱动电路,以自动检测在OLED中发生的短路故障并切换至备用OLED.该电路采用p型低温多晶硅薄膜晶体管制造.当发生短路故障时,本电路可以在不改变驱动电流的情况下,保持OLED像素的亮度维持不变.实验结果表明,本电路不仅具有容错功能,而且与标准电路相比可以显著地降低功耗.     

具有容错功能的OLED有源驱动电路

以有机电致发光器件(OLED)为基础的显示或照明器件,通常会受到短路故障的影响,从而使得像素失效,降低面板的亮度,进而严重地影响亮度的均匀性,并且会产生大量的功耗.本文介绍了一种新的有源OLED驱动电路,以自动检测在OLED中发生的短路故障并切换至备用OLED.该电路采用p型低温多晶硅薄膜晶体管制造.当发生短路故障时,本电路可以在不改变驱动电流的情况下,保持OLED像素的亮度维持不变.实验结果表明,本电路不仅具有容错功能,而且与标准电路相比可以显著地降低功耗.     

一种低功耗高速空间光调制器驱动电路

本文描述了一种新型的多量子阱空间光调制器驱动电路的设计和测试。为了解决时钟同步问题并减少功耗,我们有别于前人,将所有电路模块集成在一块芯片上。因为传统的单斜坡数模转换器无法消除电容的失配,所以我们转而采用64个列共享8位电阻串数模转换器来提供输出电压,实现0.5V至3.8V的可编程电压调控。这些数模转换器被紧密放置于6464 驱动阵列的上方力求减小失配。每个转换器消耗80uA电流,在280ns内完成一次转换。为了更快的传输速率,系统采用2级缓存,工作时钟50MHz,真刷新率达到50K帧每秒,整片功耗302mW。芯片采用0.35um CMOS工艺,面积5.5 mm7 mm。     

En Route to Wide Area Emitting Organic Light-Emitting Transistors for Intrinsic Drive-Integrated Display Applications: A Comprehensive Review

Organic light-emitting transistors (OLET) evolved from the fusion of the switching functionality of field-effect transistors (FET) with the light-emitting characteristics of organic light-emitting diode (OLED) that can simplify the active-matrix pixel device architecture and hence offer a promising pathway for future flat panel and flexible display technology. This review systematically analyzes the key device/molecular engineering tactics that assist in improving the electrode edge narrow emission to wide-area emission for display applications via three different topics, that is, narrow to wide-area emission, vertical architecture, and impact of high-κ dielectric on the device performance. Source–drain electrode engineering such as symmetric/asymmetric, planar/non-planar arrangement, semitransparent nature, multilayer approach comprising charge transport, and work function modification layers enable widening the emission zone. Vertical OLET architecture offers short channel lengths with a high aperture ratio, pixel type area emission, and stable light-emitting area. Transistors utilizing high-κ dielectric materials have assisted in lowering the operating voltage, enhancing luminance and air stability. The promising development in achieving wide-area emission provides a solid basis for constructing OLET research toward display applications; however, it relies on developing highly luminescent and fast charge transporting materials, suitable semitransparent source/drain electrodes, high-κ -dielectrics, and device architectural engineering.     

High-efficiency isolated SEPIC converter with reduced conduction losses for LED displays

This paper proposes a high-efficiency isolated bridgeless single-ended primary inductor converter (SEPIC) for light-emitting-diode (LED) displays. The proposed isolated SEPIC converter can supply LED back-light power with reduced conduction losses. Switching power losses as well as conduction losses are reduced. The proposed converter is theoretically analysed. Experimental results based on a 28 V, 300 W back-light power are discussed to verify the performance of the proposed converter.     

Data Supply Voltage Reduction Scheme for Low‐Power AMOLED Displays

This paper demonstrates a new driving scheme that allows reducing the supply voltage of data drivers for low‐power active matrix organic light‐emitting diode (AMOLED) displays. The proposed technique drives down the data voltage range by 50%, which subsequently diminishes in the peak power consumption of data drivers at the full white pattern by 75%. Because the gate voltage of a driving thin film transistor covers the same range as a conventional driving scheme by means of a level‐shifting scheme, the low‐data supply scheme achieves the equivalent dynamic range of OLED currents. The average power consumption of data drivers is reduced by 60% over 24 test images, and power consumption is kept below 25%.     

AMOLED像素电路的设计与仿真研究

为了解决驱动管阈值电压漂移带来的OLED亮度不均匀的问题,介绍了一种新的AMOLED四管像素电路,利用HSPICE仿真软件详细分析了电路各参数对其输出特性的影响,同时给出了参数设计的方法.最后从延长OLED的使用寿命出发,对电路进行了改进并根据已设计的参数进行了仿真,结果表明改进后的电路功能不变,且在驱动阶段,驱动电流...     

OLED应用于照明的发展现状及前景

有机发光二极管(OLED)具有传统照明方式所不具有的固态照明的特点,同时由于自身制作特点还具有LED所不具备的特点,OLED照明将赋予照明光源一些新的功能和涵义.在总结OLED照明研发现状的基础上,探讨了目前OLED照明尚未解决的主要技术问题,并概括分析了解决这些问题的方法.     

Optimized doping and contact scheme for low-voltage 275-nm deep ultraviolet LEDs

Deep ultraviolet light-emitting diode structures with a peak wavelength of 275 nm, as well as individual AlGaN:Mg layers, were grown by metalorganic chemical vapor deposition on (0001) silicon carbide. Control of the Mg profile in the devices reduced unwanted Mg-related emission at 320 nm to 1/224th of that emitted at the peak wavelength. An additional peak at 410 nm was observed to be related to oxygen incorporation in the film and confirmed with secondary ion mass spectroscopy (SIMS). Also investigated in an effort to improve hole injection were aluminum content, layer thickness, V/III ratio, activation temperature, and properties of the GaN:Mg contact layer and transparent contact metal stack. By optimizing this and other layers of the device, output powers of 0.84 mW at 1.3 A were obtained from packaged devices, with forward voltages as low as 4.9 V at 20 mA.     

AM-OLED的像素电路集锦(一)

用于AM-OLED的LTPS TFTs的阈值电压(Vth)和沟道迁移率(μ)在空间分布上是不够均匀的,用于AM-OLED的a-Si TFTs的Vth和μ会随时间偏移,这些缺点会造成显示屏亮度的不均匀性和不稳定性.为此,需要引入各种像素补偿电路,使显示屏发光亮度的均匀性和稳定性符合商品要求(文章分为两期刊登,本篇为第一部...     

Emission mechanism in the terbium complex doped PVK system

A new kind of rare earth (RE) complex Tb(o-MBA)3phen was synthesized and used as an emitting material in electroluminescence. The material was doped into poly(N-vinylcarbazole) (PVK) as the emitting layer,which was made by spin coating. Three kinds of devices were fabricated with the structures: (A) ITO/PVK:Tb(o-MBA)3phen/LiF/A1; (B) ITO/PVK:Tb(o-MBA)3phen/BCP/AIQ3/LiF/A1; (C) ITO/BCP/PVK:Tb(o-MBA)3phen/A1Q3/LiF/A1. Bright green emission could be obtained from device (A) and (C). The photoluminescence (PL) and electroluminescence (EL) mechanisms of this material had been investigated. Since there was an overlap between the PL spectrum of PVK and the excitation spectrum of the terbium complex, there should be a F6rster energy transfer process between them. The excitation spectrum of PVK doped Tb(o-MBA)3phen system is similar with the excitation spectrum of PVK,yet it is different from that of Tb(o-MBA)3phen. So, the emission of Tb(o-MBA)3phen should partly come from the excitation of PVK while in the organic light-emitting diode (OLED), based on Tb(o-MBA)3phen, the emission mainly comes from the direct recombination of electron and hole. Bright green emission can be obtained from the optimized multi-layer device (C) and the highest EL brightness reached 180 cd/m2 at the voltage of 17 V.     

AM-OLED的像素电路集锦（二）

用于AM-OLED的LTPS TFTs的阈值电压（Vth）和沟道迁移率（μ）在空间分布上是不够均匀的,用于AM-OLED的a-Si TFTs的Vth和μ会随时间偏移,这些缺点会造成显示屏亮度的不均匀性和不稳定性。为此,需要引入各种像素补偿电路,使显示屏发光亮度的均匀性和稳定性符合商品要求（文章分为两期刊登,本篇为第二部分）。     

基于混合配体Znq(DBM)的单色和白色OLED

以8-羟基喹啉(q)和1,3-二苯基-1,3-丙二酮定向合成了有机小分子配合物Znq(DBM),将其作为发光层制备了单色有机电致发光器件(OLED)。在结构为ITO/m-MTDATA(5nm)/NPB(40nm)/Znq(DBM)(60nm)/LiF(0.5nm)/Al(100nm)的器件中,启亮电压为5V,最大亮度达到4 575cd/m2。同时又在器件中引入间隔层BCP,研究其不同厚度对OLED性能的影响。在结构为ITO/m-MTDATA(5nm)/NPB(40nm)/BCP(x nm)/Znq(DBM)(60nm)/LiF(0.5nm)/Al(100nm)的器件中,当BCP层厚为0nm时,发光颜色为黄绿色;当BCP层厚为1nm时,发光颜色为白色,色坐标为(0.29,0.33),最大亮度为2 231cd/m2;当BCP层厚为5nm时,发光颜色为蓝色。根据器件结构和性能,讨论了其内部机理。     

利用石墨烯掺杂在NPB中的OLED性能研究

采用NPB掺杂石墨烯作为空穴传输层,制备有机电致发光器件(OLED),器件结构为ITO/NPB:Graphene(20wt.%)(50nm)/Alq3(80nm)/LiF(0.5nm)/Al(120nm)。将其与标准器件ITO/NPB(50nm)/Alq3(80nm)/LiF(0.5nm)/Al(120nm)作性能比较,研究石墨烯对OLED性能的影响。结果表明,在NPB中掺杂石墨烯薄层的器件,在同等条件下性能最佳,当电流密度为90mA/cm2时器件电流效率达到最大值3.40cd/A,与标准器件最高效率相比增大1.49倍;亮度在15V时达到最大值10 070cd/m2,比标准器件最大亮度增大5.16倍。