基于垂直结构的有机薄膜晶体管

介绍了基于垂直结构的有机薄膜晶体管的器件结构、工作原理以及相关的研究进展。通过对垂直结构的有机薄膜晶体管的特性分析,探讨了采用这种结构的有机薄膜晶体管驱动有机发光二极管的可行性。此项研究为发展新型全有机的柔性显示器提供了新的思路。     

驱动电子墨水电子纸的柔性TFT背板制造技术

基于电子墨水技术的电子纸是目前最有竞争力的类纸媒显示器。实现电子墨水电子纸的柔性是这项显示技术的关键之一。文章分析了当前电子墨水电子纸的主要研究方向,详细介绍了基于金属柔性基板的TFT制造技术、基于固定塑料基板的以激光释放塑基电子工艺(EPLaR)为代表的TFT制造技术、以激光退火表面释放技术(SUFTLA)为代表的TFT转移技术以及有机薄膜晶体管(OTFT)技术等4项柔性TFT背板的主要实现方法。对比了它们的材料选取,工艺特点和器件性能,分析了各项柔性TFT背板工艺的优缺点,提出了改进方向。     

新颖平板显示技术

近年来，有机薄膜晶体管技术发展非常迅速。它具有制作温度低和成本低的特点，可制成一种新颖平板显示器。本文介绍了有机高分子聚合物材料和导电有机高分子聚合物材料及其应用，有机半导体及其光电特性及在柔性塑料上制成视频平板显示器。     

有机发光晶体管的研究进展

兼备有机发光二极管及薄膜场效应晶体管特性的有机发光晶体管(OLET)不仅可能取代薄膜晶体管驱动的液晶显示,应用于大面积的全有机有源矩阵柔性显示中,还在集成电路信号处理等方面具有潜在的应用价值.文章概述了OLET的发展进程,并从器件结构、工作原理和材料等方面对其进行了概述.     

喷墨印制导电墨水研究进展

喷墨印制电子技术是一种无接触式、无压力、无需印版的电子产品制造技术。因具有制造速度快、环境友好、工艺过程简单、成本低、功能多样化、基材适用性广以及定位精确等特点受到人们的广泛关注,成为电子制造产业发展的新方向。导电墨水作为导电图形的基础材料,是印制电子技术发展的瓶颈,直接影响着电子产品的性能及质量。本文介绍了喷墨印制用导电墨水的导电机理、物理参数,以及碳系和银系墨水、液体金属墨水等的最新研究进展,并分析了导电墨水在RFID、PCB电路、太阳能电池、有机发光二极管、薄膜晶体管等领域的应用概况。分析表明,目前导电墨水的制备技术已取得一定进步,但相关的制备理论不成熟,缺乏优良的助剂和价格适宜的喷墨印制设备,未来急需开发具有低处理温度、高稳定性的喷墨印制导电墨水。     

有机薄膜晶体管阵列面向电子纸像素设计

讨论了有机薄膜晶体管(Organic Thin Film Transistor,OTFT)作为开关器件来驱动电子纸的像素设计,特别是像素电路结构、HSPICE模拟用模型参数和像素平面结构。讨论了有机薄膜晶体管制造过程,并用HSPIC模拟分析了有机薄膜晶体管结构和存贮电容大小对像素波形的影响,结果表明TFT结构的选择依赖于存贮电容的大小。     

双栅酞菁铜有机薄膜晶体管

有机薄膜晶体管以其成本低、柔性好、易加工等优点越来越受到人们的青睐,目前已广泛应用于低端器件。为了获得更实际的应用,OTFTs的性能还需进一步的提高和改善。文章中以酞菁铜(CuPc)为有机半导体材料,制备了双栅结构的有机薄膜晶体管,其阈值电压为-4.5V,场效应迁移率0.025cm2/V.s,开关电流比Ion/Ioff达到9.8×103,与单栅有机薄膜晶体管相比,双栅器件在更低的操作电压下获得了更大的输出电流,场效应迁移率更高,而且通过对两个栅压的调节,对导电沟道实现了更好的控制,器件性能有了较大的提高。     

有机薄膜晶体管(OTFT)的研究进展

有机薄膜晶体管(organic thin film transistor,OTFT)具有工艺简单、成本低及柔韧性良好等优点,成为下一代显示技术的研究焦点.本文综述了有机薄膜晶体管的研究现状和未来的发展趋势,比较了采用不同材料的OTFT器件的性能,总结了影响OTFT性能的两大主要因素,即栅极绝缘层与有机有源层之间的界面特性和有机有源层与源/漏电极之间欧姆接触电阻的大小,并详细综述了改善OTFT性能的最新方法和研究成果.     

2015年全球存储芯片市场规模将达216亿美元

据市场研究公司NanoMarkets最新发表的研究报告称，包装、显示屏、智能卡、传感器等行业对柔性大面积电子电路的需求将推动有机晶体管和存储芯片市场，2015年将达到216亿美元。虽然有机存储芯片的增长低于有机薄膜晶体管的增长，但是，它将迅速赶上来。到2015年，将有价值161亿美元的电子产品中将包含有机存储芯片。这篇报告的要点包括：     

有机薄膜晶体管研究进展

有机薄膜晶体管是一种受到日益重视和正被广泛研究的新型电子器件。本文论述了有机薄膜晶体管的优点、基本结构、材料以及近几年来国外在该领域的最新研究进展。并对有机薄膜晶体管的应用前景做了展望。     

Fully solution-processed organic thin-film transistors by consecutive roll-to-roll gravure printing

A high-performance/flexible organic thin-film transistor (OTFT) is fabricated by using all-step solution processes, which are composed of roll-to-roll gravure, plate-to-roll gravure and inkjet printing with the least process number of 5. Roll-to-roll gravure printing is used to pattern source/drain electrodes on plastic substrate while semiconductor and dielectric layers are printed by consecutive plate-to-roll gravure printing. Finally, inkjet printing of Ag organometallic ink is used to pattern the gate electrode. The fabricated OTFT exhibits excellent electrical performance, field-effect mobility over 0.2 cm²/Vs, which is one of the best compared to the previous works. The deposition of a self-assembled monolayer on the source-drain electrodes results in a higher work function which is suitable for a p-type polymer semiconductor. Moreover, the formation of dense gate electrode line on hydrophobic dielectric is achieved by selecting suitable Ag ink.     

An Inkjet‐Printed Field‐Effect Transistor for Label‐Free Biosensing

A flexible, biological field‐effect transistor (BioFET) for use in biosensing is reported. The BioFET is based on an organic thin‐film transistor (OTFT) fabricated mainly by inkjet printing and subsequently functionalized with antibodies for protein recognition. The BioFET is assessed for label‐free detection of a model protein, human immunoglobulin G (HIgG). It is characterized electrically to evaluate the contribution of each step in the functionalization of the OTFT and to detect the presence of the target protein. The fabrication, structure, materials optimization, electrical characteristics, and functionality of the starting OTFT and final BioFET are also discussed. Different materials are evaluated for the top insulator layer, with the aim of protecting the lower layers from the electrolyte and preserving the BioFET electrical performance.     

High-resolution inkjet-printed organic thin film transistor array with commercially applicable source-drain electrode process

High-resolution inkjet printing of an organic thin film transistor (OTFT) array for mass-production is still regarded as an immature technology due to the difficulty in controlling the dimension of pattern and registry with other layers in commercial large-scale substrates. Especially, in the case of on organic gate insulator (OGI) in an inkjet-printed OTFT array, it is impossible to use plasma pre-treatment of the OGI for the hydrophobicity required for high-resolution inkjet printing of an organic semiconductor (OSC) due to its non-selectivity between organic layers, both inside and outside the channel area. A novel and commercially applicable process of the source-drain (SD) electrode prior to inkjet printing of the OSC in the bottom contact structure not only allowed a selective plasma treatment for high-resolution inkjet printing of OSC on OGI without the extra photolithographic process, but also protected the channel interface from the harmful outcomes of wet or plasma processes. This method enabled uniform electrical characteristics of more than 300 thousand pixels of an OTFT array for a backplane. Based on these results, a 5.7 inch electrophoretic display (EPD), with a high resolution of 140 dots per inch (DPI), on a plastic substrate was successfully demonstrated.     

Automated fabrication of hybrid printed electronic circuits

Printed electronics offer great potential for new applications such as Internet of Things devices and wearables. However, to date, only a limited number of electronic functions and integration densities can be realised by printing processes. Hence, hybrid printed electronic circuits are actually created by mounting silicon electronic components. Since both printed materials and processes are continuously evolving, an accompanying structured development methodology is required. This paper highlights a digital workflow from design to automated fabrication using the example of a demonstrator circuit. A multi-layer vector ink-jet printing process to print electronic devices onto foil substrates with three functional inks is presented. This printing process is improved using a newly set-up printing system: Integrating a piezo print head into the path planning of the printing system and its control as a virtual stepper axis enable highly precise vector printing. This leads to printed resistors with low tolerances. Adaptations of surface mount technology for assembling silicon electronic components onto printed foil substrates are discussed. Finally, image processing methods to cope with deformations of the flexible foil substrates in the fabrication process are introduced.     

Fabrication of organic flexible electrodes using transfer stamping process

A transfer stamping process is proposed to fabricate micro-scale organic flexible electrodes. With different adhesion forces of the transferring interfaces, ink/mold and ink/substrate, patterns are formed from the relief features of the elastomeric mold to the substrate without residual layer, and no complex pre-process and steps are needed. To estimate the deformation during pressing, the sagging height of the mold is analyzed with finite element method (FEM). Two conductive polymers, PEDOT:PSS and silver paste, are transferred from the flat relief features of the mold to the PET substrate. The coating characteristics and problems are discussed. The transfer stamping process is also employed to fabricate electrodes on the dielectric/ITO film and to form an organic flexible capacitance. This paper demonstrates the potential of transfer stamping in fabricating organic electronic components, such as organic integrated circuit, OLED and OTFT.     

High-performance thin-film transistor with 6,13-bis(triisopropylsilylethynyl) pentacene by inkjet printing

We have studied the performance improvement of organic thin-film transistor (OTFT) with a solution based TIPS pentacene (6,13-bis(triisopropylsilylethynyl)pentacene) by inkjet printing. The TIPS pentacene with 1.0 wt.% solution in 1,2-dichlorobenzene was used for printing of an active layer of OTFT. The OTFT printed at room temperature shows a shoulder-like behavior but it disappears for the OTFT printed at the substrate temperature of 60 °C. The OTFT on plastic exhibited an on/off current ratio of ∼10⁷, a threshold voltage of −2.0 V, a gate voltage swing of 0.6 V/decade and a field-effect mobility of 0.24 cm²/Vs in the saturation region.     

Transparent Nanopaper‐Based Flexible Organic Thin‐Film Transistor Array

Eco‐friendly and low‐cost cellulose nanofiber paper (nanopaper) is a promising candidate as a novel substrate for flexible electron device applications. Here, a thin transparent nanopaper‐based high‐mobility organic thin‐film transistor (OTFT) array is demonstrated for the first time. Nanopaper made from only native wood cellulose nanofibers has excellent thermal stability (>180 °C) and chemical durability, and a low coefficient of thermal expansion (CTE: 5–10 ppm K^‐1). These features make it possible to build an OTFT array on nanopaper using a similar process to that for an array on conventional glass. A short‐channel bottom‐contact OTFT is successfully fabricated on the nanopaper by a lithographic and solution‐based process. Owing to the smoothness of the cast‐coated nanopaper surface, a solution processed organic semiconductor film on the nanopaper comprises large crystalline domains with a size of approximately 50–100 μm, and the corresponding TFT exhibits a high hole mobility of up to 1 cm²V^‐1 s^‐1 and a small hysteresis of below 0.1 V under ambient conditions. The nanopaper‐based OTFT also had excellent flexibility and can be formed into an arbitrary shape. These combined technologies of low‐cost and eco‐friendly paper substrates and solution‐based organic TFTs are promising for use in future flexible electronics application such as flexible displays and sensors.     

Printing-induced improvements of organic thin-film transistors

To understand the observation of improved pentacene (Pn) thin-film transistor mobility in flexible printed devices, a method for performing electrical measurements of organic thin-film transistors (OTFT) during the process of transfer printing has been developed. Different sample configurations were designed to test two aspects of the printing process: (1) the formation of the source/drain contacts a Pn thin-film, and (2) the formation of the transfer printed Pn/dielectric interface. In situ measurements show that pressure-induced contacts of gold (Au) electrodes result in a factor of seven mobility improvement compared with evaporation of top Au electrodes on an otherwise identical device configuration. Annealing the laminated device up to 90 °C caused no further improvement, and heating above 90 °C degraded performance. The mobility of a transfer printed device with the rough, as-grown top surface of the Pn in contact with the dielectric was found to increase dramatically with subsequent annealing for a sample temperature up to 120 °C. This is attributed to annealing-induced structural changes in the Pn film at elevated temperatures, consistent with X-ray bulk measurements showing enhanced crystal morphology in transfer printed Pn thin-films.     

Prospects of manufacturing organic semiconductor-based integratedcircuits

The driving force for developing organic thin-film transistor (OTFT)-based electronics is the fact that they are flexible, lightweight and have the prospect of low-cost manufacturing. Major barriers in the practical realization of OTFT-based electronic systems are the need for larger power supplies, lower gain, lower switching speeds and reliability problems. New directions leading to changes in the design of transistors, materials used in the fabrication, and processing techniques are warranted for developing process and equipment that can lead to the manufacturing of OTFT-based electronics. For developing dense OTFT-based electronics, the low thermal conductivity (as compared to silicon) of organic semiconductors is a fundamental problem. The use of nanodimension polymers with homogeneous microstructure, transistors operating in subthreshold region and the use of new materials (high and low dielectric constant dielectric materials as well as Cu as the conductor for interconnections) for fabricating transistors and a novel rapid photothermal processing technique for depositing thin films of organic semiconductors as well as for reducing the defects introduced during processing are some of the proposed directions that may lead to the manufacturing of OTFT based electronics