High-speed low-power voltage-programmed driving scheme for AMOLED displays

A new voltage-programmed driving scheme named the mixed parallel addressing scheme is presented for AMOLED displays, in which one compensation interval can be divided into the first compensation frame and the consequent N-1 post-compensation frames without periods of initialization and threshold voltage detection. The proposed driving scheme has the advantages of both high speed and low driving power due to the mixture of the pipeline technology and the threshold voltage one-time detection technology. Corresponding to the proposed driving scheme, we also propose a new voltage-programmed compensation pixel circuit, which consists of five TFTs and two capacitors(5T2C). In-Zn-O thin-film transistors(IZO TFTs) are used to build the proposed 5T2C pixel circuit. It is shown that the non-uniformity of the proposed pixel circuit is considerably reduced compared with that of the conventional 2T1C pixel circuit. The number of frames(N) preserved in the proposed driving scheme are measured and can be up to 35 with the variation of the OLED current remaining in an acceptable range. Moreover, the proposed voltage-programmed driving scheme can be more valuable for an AMOLED display with high resolution, and may also be applied to other compensation pixel circuits.     

基于物理并适用于电路仿真的多晶硅薄膜晶体管薄层电荷模型

本文利用薄层电荷理论,建立了一个基于表面势的、物理的多晶硅薄膜晶体管(Polysilicon Thin-Film Transistors,poly-Si TFTs)的电流模型,且该模型适用于电路仿真.推导了 poly-Si TFTs 表面势的近似解法,该求解法非迭代的计算大大地提高了计算效率,且精确度高并得到实验验证.基于物理的迁移率方程考虑了晶界势垒高度,和由于声子散射与表面粗糙散射引起的迁移率退化.基于 Brews 的薄层电荷模型和上述非迭代计算表面势,本电流模型同时考虑了漏致势垒降低(DIBL)效应、kink 效应和沟道长度调制效应.对不同沟长的器件实验数据比较发现,提出的模型在很广的工作电压内与实验数据符合得非常好.同时本模型的所有方程都具有解析形式,电流方程光滑连续,适用于电路仿真器如 SPICE.     

磁镜场约束中粒子运动的数值计算

由单粒子轨道理论,从分析磁镜场中荷电粒子的受力情况出发,应用计算机数值求解方法模拟了磁镜场中荷电粒子的运动情况.结果表明:与经典的理论分析结果不同,当荷电粒子的起始位置与磁轴的距离不等于其拉摩尔半径时,荷电粒子在平行磁轴方向和垂直磁轴平面中的速度分量存在着周期性变化,其周期为荷电粒子的拉摩尔周期;同时其损失锥的临界角随着荷电粒子起始位置与磁轴的距离的增大而略有减小.     

IGZO TFT与ZnO TFT的性能比较

分析比较了ZnO TFT与IGZO TFT的主要光电学特性以及阈值电压稳定性。结果表明:ZnO薄膜与IGZO薄膜在可见光波长范围内都有着较高的光学透过率;在同等制备条件下,IGZO TFT器件的场效应迁移率、开关电流比、阈值电压及亚阈值系数等方面的特性均明显好于ZnO TFT;二者都有着较低的泄漏电流,并且差别很小。另外,ZnO TFT在正负偏压下阈值电压都有漂移,而IGZO TFT在正偏压下阈值电压漂移比ZnO TFT的小且在负偏压下阈值电压没有漂移,由此可见IGZO TFT比ZnO TFT有着更好的稳定性。总之,IGZO薄膜比ZnO薄膜更适合作为下一代TFT的有源层材料。     

基于labVIEW的AM-OLED显示屏测试系统

为方便对AM-OLED显示屏的各项性能进行测试,本文设计了基于labVIEW(Laboratory Virtual Instrument Engineering Workbench实验室虚拟仪器工程平台)的AM-OLED显示屏V-I-L曲线自动化测试系统,实现了在同一个软件下对显示屏的电压、电流、亮度、色坐标等特性的测试。首先,构建硬件电路即基于FPGA的AM-OLED显示屏驱动电路。接着,在此基础上利用labVIEW平台设计了AM-OLED显示屏V-I-L曲线测试系统的软件系统。最后,利用该系统对自主研发的基于MOTFT技术的12.2cm(4.8in)AM-OLED显示屏进行了测试,验证了系统的可靠性。通过对测试结果进行分析,AM-OLED显示屏达到设计亮度时各像素所需的数据电压约为9.2V。总之,本系统实现了对显示屏性能参数的自动化测试,为显示屏的白平衡调节和AMOLED专用驱动芯片设计提供了数据支持,为显示屏的优化设计指明方向。     

多晶硅薄膜晶体管中的晶粒间界电荷分享效应

通过对晶粒间界两侧耗尽区建立准二维模型,研究晶粒间界电荷分享效应对多晶硅薄膜晶体管阈值电压的影响.研究表明,考虑了晶粒间界电荷分享效应的阈值电压将变小,其中晶粒尺寸对阈值电压的影响最大.在此基础上,建立了多晶硅薄膜晶体管的阈值电压解析模型.     

多晶硅薄膜晶体管Kink效应研究与建模

多晶硅薄膜晶体管(P-Si TFTs)技术在SOP(system on panel)显示应用中发挥着越来越重要的作用.随着尺寸的不断缩小,P-si TFT 的Kink效应越来越明显,对有源液晶显示矩阵和驱动电路的性能影响很大.对发生Kink效应的物理机制、二雏数值仿真及其一维解析模型进行了分析,讨论了晶粒边界、沟道长度与Kink效应的关系,提出建立适合电路仿真的一维解析模型的关键与展望.     

多晶硅薄膜晶体管亚阈值区准二维模型(英文)

从准二维泊松方程出发,结合多晶硅扩散和热发射载流子输运理论,建立了多晶硅薄膜晶体管亚阈值电流模型。由表面势方程及亚阈值电流方程求得包含陷阱态和晶粒尺寸的亚阈值斜率解析表达式。模型具有简明的表达式,并且在大晶粒和低陷阱态情形下可简化为传统长沟道MOSFET亚阈值区模型。仿真结果与试验数据符合得很好,验证了模型的正确性。     

氧化锌基TFT稳定性研究进展

总结了氧化锌基TFT稳定性的最新研究进展,分析了栅偏压、栅绝缘层和背沟道影响TFT稳定性,尤其是阈值电压稳定性的主导机制.结果表明,氧化锌基TFT的不稳定性主要取决于陷阱缺陷态对可动载流子的俘获作用,以及新陷阱态的产生.总结了提高氧化锌基TFT稳定性的三种途径:降低栅偏压;提高沟道/栅绝缘层界面质量,降低缺陷态密度;钝化保护背沟道.     

一种基于低温多晶硅薄膜晶体管的交流AMOLED像素补偿电路

This paper presents a new poly-Si pixel circuit employing AC driving mode for active matrix organic light-emitting diode （AMOLED） displays. The proposed pixel circuit, which consists of one driving thin-film tran- sistor （TFT）, three switching TFTs, and one storage capacitor, can effectively compensate for the threshold voltage variation in poly-Si and the OLED degradation. As there is no light emission, except for during the emitting period, and a small number of devices used in the proposed pixel circuit, a high contrast ratio and a high pixel aperture ratio can be easily achieved. Simulation results by SMART-SPICE software show that the non-uniformity of the OLED current for the proposed pixel circuit is significantly decreased （〈 10%） with an average value of 2.63%, while that of the conventional 2T1C is 103%. Thus the brightness uniformity of AMOLED displays can be improved by using the proposed pixel circuit.