一种新型a-IGZO TFT集成栅极驱动电路设计

在传统集成栅驱动电路中采用非晶InGaZnO薄膜晶体管(a-IGZO TFT)后会造成信赖性的降低,经过分析确定原因为驱动TFT阈值电压漂移。本文提出了一种改进的集成栅驱动电路,通过对驱动TFT栅节点电压的稳定控制,获得了较大的驱动TFT阈值电压漂移冗余度(从原来的不到±-3V扩大到±-9V),克服了a-IGZO TFT阈值电压漂移所造成的电路失效,稳定了集成栅驱动电路并延长了液晶显示器面板的寿命。     

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.     

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.     

3.5‐Inch QCIF AMOLED Panels with Ultra‐low‐Temperature Polycrystalline Silicon Thin Film Transistor on Plastic Substrate

In this paper, we describe the fabrication of 3.5‐inch QCIF active matrix organic light emitting display (AMOLED) panels driven by thin film transistors, which are produced by an ultra‐low‐temperature polycrystalline silicon process on plastic substrates. The over all processing scheme and technical details are discussed from the viewpoint of mechanical stability and display performance. New ideas, such as a new triple‐layered metal gate structure to lower leakage current and organic layers for electrical passivation and stress reduction are highlighted. The operation of a 3.5‐inch QCIF AMOLED is also demonstrated.     

Extraction of trap densities in entire bandgap of poly-Si thin-film transistors fabricated by solid-phase crystallization and dependence on process conditions of post annealing

Trap densities (D_t) in entire bandgaps of poly-Si thin-film transistors (TFTs) fabricated by solid-phase crystallization (SPC) have been extracted by measuring low-frequency capacitance-voltage characteristics and using an extraction algorithm. The extraction algorithm is explained in detail. D_t in the upper and lower halves of the bandgap is extracted from n- and p-type TFTs, respectively. It is found that D_t is very roughly 10¹⁸ cm⁻³ eV⁻¹ near the midgap and becomes tail states near the conduction and valence bands. As a result, D_t is distributed like U shape in the bandgap, but humps appear around the midgap. Moreover, the dependence of D_t on process conditions of post annealing has been evaluated. It is found that the hump can be reduced by increasing annealing temperature and time because crystal defects generated during the SPC are extinguished during the post annealing.     

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。     

Analysis and simulation of reddish overshoot in active matrix organic light-emitting diode display with varying p-doped hole transport layer concentrations

A typical organic light-emitting diode (OLED) display has common organic layers between adjacent pixels, which ensure ease of manufacturing process and efficiency in operation. The p-doped hole transport layer (p-HTL) has low electrical resistivity, which results in a high efficiency OLED. However, the low resistivity results in various side effects, including color crosstalk and overshoot, mainly due to lateral leakage current flowing through this layer. Furthermore, virtual reality and augmented reality devices that require extremely high pixels per inch (PPI) and superior image quality are very sensitive to lateral leakage current. In this study, we propose a passive driving panel based on RGB top emission to efficiently measure and model the lateral leakage current characteristics according to the p-HTL concentration.In addition, we constructed a 1.5-inch active matrix organic light-emitting diode panel based on the n-type low-temperature polycrystalline silicon 4T2C pixel circuit. Subsequently, we quantitatively analyzed the reddish overshoot phenomenon during the black to white image transition. This effect was reduced at p-HTL concentrations under 1%.Finally, we analyzed the overshoot mechanism through SPICE simulations and realized the optimal lateral resistance value of the common organic layer for each PPI.     

Modeling the impact of light on the performance of polycrystalline thin-film transistors at the sub-threshold region

The impact of the light illumination on the drain current of polycrystalline silicon thin-film transistors (TFT) is studied in this work. The increase of the output current as a result of raised light intensity is modeled, based on measured experimental data for different V_ds and V_gs values and transistor sizes W/L. The proposed model has been verified against the measurements and the simulated output characteristics give a good approximation in the sub-threshold region.     

有机半导体器件的现状及发展趋势

从上世纪末和本世纪初开始,有机半导体材料研究引起了业界的广泛重视,使有机半导体器件的实验室制作水平得到大幅提高,并逐步进入当前的商品发展阶段。概述了有机半导体的发展历程、各种器件结构与特性及其技术现状;介绍了有机发光二极管(OLED)、太阳电池以及其他有机半导体器件的应用概况;探讨了有机半导体优于Si和GaAs等典型无机半导体技术的特点,分析讨论了有机半导体技术的发展前景;指出有机半导体器件有望成为解决传统半导体技术问题的有效途径。     

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）。     

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.     

Electrochromic display cells driven by an electrolyte-gated organic field-effect transistor

Monolithic integration of an organic field-effect transistor (OFET) and an organic electrochromic display cell operating at around 1 V is reported. This was achieved by utilising a common patterned layer of poly(styrenesulfonic acid) (PSSH). In the OFET, PSSH served as the electric double layer capacitors between the gate and the organic semiconductor channel. In the electrochromic pixel, PSSH was included as the electrolyte and transports protons from and to the electrochromic layer upon switching. The enhancement mode OFET enables a relatively faster updating speed, of the display cell, and provides a much simpler addressing and updating scheme as compared to smart pixels including a depletion mode electrochemical transistor.     

新型热释电材料及其在红外探测器中的应用

以(1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3{PMNT[(1-x)/x}为代表的大尺寸、高质量弛豫铁电单晶具有非常高的热释电系数、探测优值和较低的热扩散系数,其综合热释电性能远优于传统的热释电材料.概述了PMNT[(1-x)/x]单晶、掺锰PMNT(74/26)单晶和0.42Pb(In1/2Nb1/2)...     

基于有机p型掺杂电荷产生层制备叠层式白光OLED的研究

基于新型有机p型掺杂的电荷产生层,制备了叠层式白光有机发光二极管(OLED).有机p型掺杂层具有很高的导电率,可以在不影响器件电学特性的前提下,通过改变该层的厚度来优化白光OLED的器件性能,调节器件的光色.与传统白光OLED相比,文章研究的叠层式白光OLED制备工艺简单、电荷产生效率高,可应用于平板显示与固态照明.     

高反射性电流阻挡层用于提高InGaN/GaN发光二极管的光输出功率

由SiO₂/TiO₂分布布拉格反射镜(DBR)和Al镜组成的混合式反射电流阻挡层用于提高InGaN/GaN发光二极管的光输出功率。混合式反射电流阻挡层不仅增强了电流扩展效应而且有效的将射向p金属电极的光子反射防止其对p电极焊点附近光子的吸收。实验结果表明,淀积在p-GaN上1.5个周期的SiO₂/TiO₂DBR和Al镜在455nm垂直入射时的反射率高达97.8%。在20mA的工作电流下,与没有电流阻挡层的发光二极管相比,生长1.5对SiO₂/TiO₂ DBR和Al镜作为电流阻挡层的发光二极管的光输出功率提高了12.5%,且光输出功率的分布更加均匀。     

A dry-patterned Cu(Mg) alloy film as a gate electrode in a thin-film transistor liquid crystal display

The annealing of a Cu(4.5at.%Mg)/SiO₂/Si structure in ambient O₂ at 10 mtorr and 300–500°C allows for the out-diffusion of the Mg to the Cu surface, forming a thin MgO (15 nm) layer on the surface. The surface MgO layer was patterned and successfully served as a hard mask for the subsequent dry etching of the underlying Mg-depleted Cu films using an O₂ plasma and hexafluoroacetylacetone (H(hfac)) chemistry. The resultant MgO/Cu structure, with a taper slope of about 30°, shows the feasibility of dry etching of Cu(Mg) alloy films using a surface MgO mask scheme. A dry-etched Cu(4.5at.%Mg) gate a-Si:H thin-film transistor (TFT) has a field-effect mobility of 0.86 cm²/Vs, a subthreshold swing of 1.08 V/dec, and a threshold voltage of 5.7 V. A novel process for the dry etching of Cu(Mg) alloy films that eliminates the use of a hard mask, such as Ti, and results in a reduction in the process steps is reported for the first time in this work.     

Carbon nanotube field effect transistors for high performance analog applications: An optimum design approach

There is a need to explore circuit designs in new emerging technologies for their rapid commercialization to extend Moore’s law beyond 22 nm technology node. Carbon nanotube based transistor (CNFET) has significant potential to replace CMOS in the future due to its better electrostatics and higher mobility. This paper presents a complete optimal design of an inverting amplifier in CMOS, CNFET and hybrid technologies. We investigate and conceptually explain the performance measure of the amplifier at 32 nm technology node in terms of operating voltage, number of carbon nanotubes (CNT), diameter and pitch (inter-nanotube distance) variations of carbon nanotubes in a CNFET transistor in pure and hybrid technologies for area, power and performance optimization. This paper also explores the scope, possibilities and challenges associated with pure CNFET and hybrid amplifiers. We have found that pure CNFET amplifier provided good amplification while hybrid pCNFET-nMOS amplifier offered excellent frequency response and pMOS-nCNFET amplifier gave better transient performance compared with planar CMOS.     

高亮度微腔有机电致发光器件

为了实现有机电致发光器件(OLED)发射光谱的窄化和高亮度,真空热蒸镀具有不同微腔结构的OLED(MOLED):玻璃衬底/分布式布拉格反射器(DBR)(1～4对的SiO2/Ta2O5层)/ITO/空穴传输层(HTL,α-NPD)/发光层(EML,Alq3:Rubrene或Alq3:Coumarin6)/电子传输层(ERL,Alq3)LiF/Mg/Ag,其中沉积DBR结构采用电子束沉积法。实验表明:该MOLED的发射光谱半波长宽度(FWHM)随DBR层数的增加而减小至最小值10nm;并且在2层DBR时,掺杂Rubrene器件得到更大的电流效率,约20cd/A,最大亮度为2.6×105cd/m2。研究发现,蓝光MOLED能够对自发光产生吸收现象,降低了出光效率。     

Analysis of interface recombination and self-absorption effect on the performance of QWIP-HBT-LED integrated device

In this paper, the effect of interface recombination and self-absorption within the light emitting diode (LED) active region on the efficiency of QWIP-HBT-LED integrated device is considered. This device is composed of a quantum well infrared photodetector (QWIP), a heterojunction bipolar transistor (HBT) and an LED. The evaluation is based on solving the continuity equation describing the carrier diffusion within the LED active region. Analytical expression describing the effect of self-absorption and surface recombination on the LED quantum efficiency is derived. In addition, the active region width and all interested device parameters are involved. It is observed that the quantum conversion efficiency of the device under consideration is degraded by the self-absorption and interface recombination within the recombined region of the LED. Also, the quantum conversion efficiency of the device is increased with the increase of the LED active region as long as the recombination velocity is above a specified value, while it is decreased with the increase of the LED active region as long as the recombination velocity is below this specified value.     

Hydrogen-assisted low-temperature plasma-enhanced chemical vapor deposition of thin film encapsulation layers for top-emission organic light-emitting diodes

In this work, we developed a single high-performance SiN_x encapsulation layer that can be directly integrated into organic devices by low-temperature plasma-enhanced chemical vapor deposition (PECVD). We investigated a hydrogen-assisted low-temperature PECVD process at a temperature of 80 °C. The thin film density improved with an increased hydrogen gas ratio, and the moisture permeability was less than 5 × 10⁻⁵ g/m²·day. To verify the stability of the PECVD process, we applied the SiN_x encapsulation layer directly to top-emitting organic light-emitting diodes. The results showed minor changes in the current-density–voltage characteristics after the PECVD process, as well as high reliability after a water dipping test.