高性能有机薄膜晶体管(OTFT)制备及其导电机制

详细介绍了在SiO2和高kHfO2介质层上制备并五苯薄膜晶体管方面的研究,特别是利用原子力显微技术(AFM)和静电力显微技术(EFM)研究了并五苯分子初始生长模式,揭示了衬底形貌、表面化学性能(包括化学清洗和聚合物层修饰)对有机半导体成膜结构和薄膜场效应晶体管性能之间的关联,包括晶体管迁移率、开关比和阈值电压等;针对并五苯初始生长成核模式的差异,分析了不同岛(畴)间畴边界对载流子在有机薄膜内输运的影响,有助于理解有机半导体薄膜导电机理。通过优化和控制介电层和有机半导体薄膜层的界面化学性质,在SiO2介质层上成功制备出迁移率为1.0cm2/V.s、开关电流比达到106的OTFT器件;在高kHfO2介质层上获得的OTFT器件的工作电压在-5V以下,开关电流比达到105,载流子迁移率为0.6cm2/V.s;器件性能指标已经达到目前国际上文献报道的最好水平。     

新型Al/Mo底电极的顶发射有机发光二极管性能研究

提出了一种新型底电极结构,使用铝钼双层薄膜作为顶发射有机发光二极管的底电极。同时分别从底电极结构、顶电极结构、空穴注入以及出射光谱等方面对器件性能进行分析和优化,最终得到的器件电流效率达到6Cd/A以上,比优化前的器件效率提高了5倍以上,加强了对TEOLED器件的性能影响因素的理解。同时也比Mo作为底电极时的器件性能实现了提高,展示了此电极结构在顶发射OLED中的应用潜力,为下一步在硅基OLED显示器件中的应用打下基础。     

High-Gain Chemically Gated Organic Electrochemical Transistor

Organic electrochemical transistors (OECTs) have exhibited promising performance as transducers and amplifiers of low potentials due to their exceptional transconductance, enabled by the volumetric charging of organic mixed ionic/electronic conductors (OMIECs) employed as the channel material. OECT performance in aqueous electrolytes as well as the OMIECs’ redox activity has spurred a myriad of studies employing OECTs as chemical transducers. However, the OECT's large (potentiometrically derived) transconductance is not fully leveraged in common approaches that directly conduct chemical reactions amperometrically within the OECT electrolyte with direct charge transfer between the analyte and the OMIEC, which results in sub-unity transduction of gate to drain current. Hence, amperometric OECTs do not truly display current gains in the traditional sense, falling short of the expected transistor performance. This study demonstrates an alternative device architecture that separates chemical transduction and amplification processes on two different electrochemical cells. This approach fully utilizes the OECT's large transconductance to achieve current gains of 10³ and current modulations of four orders of magnitude. This transduction mechanism represents a general approach enabling high-gain chemical OECT transducers.     

Improving Ideality of P-Type Organic Field-Effect Transistors via Preventing Undesired Minority Carrier Injection

Electron injection plays a crucial role in arousing the double-slope characteristics for p-type organic field-effect transistors (OFETs) with narrow-bandgap organic semiconductors (OSCs). This issue will not only result in the misrepresentation of OFET performance but also may cause device instability, hence impeding their further development in real-world applications. A facile and highly efficient approach is developed to circumvent this issue by implementing modification on the electrode/organic semiconductor interface. An ultrathin layer of wide-bandgap OSC with suitable energy levels is introduced to block the undesirable electron injection. By this means, typical double-slope behaviors and bias stress stability in the p-type OFETs can be significantly improved. Using 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene-based OFETs the double-slope behaviors of as-fabricated devices are effectively converted to near-ideal behaviors after modification, leading to a dramatic improvement of average reliability from 65.11% to 91.76%. Furthermore, the positive drift of transfer curves under prolonged bias stress is also successfully suppressed. This strategy demonstrates good universality and can provide a new guideline for the fabrication of OFETs with ideal behaviors.     

Piezoelectricity of the Transmembrane Protein ba3 Cytochrome c Oxidase

Controlling the electromechanical response of piezoelectric biological structures including tissues, peptides, and amino acids provides new applications for biocompatible, sustainable materials in electronics and medicine. Here, the piezoelectric effect is revealed in another class of biological materials, with robust longitudinal and shear piezoelectricity measured in single crystals of the transmembrane protein ba₃ cytochrome c oxidase from Thermus thermophilus. The experimental findings from piezoresponse force microscopy are substantiated using a range of control measurements and molecular models. The observed longitudinal and shear piezoelectric responses of ≈ 2 and 8 pm V⁻¹, respectively, are comparable to or exceed the performance of commonly used inorganic piezoelectric materials including quartz, aluminum nitride, and zinc oxide. This suggests that transmembrane proteins may provide, in addition to physiological energy transduction, technologically useful piezoelectric material derived entirely from nature. Membrane proteins could extend the range of rationally designed biopiezoelectric materials far beyond the minimalistic peptide motifs currently used in miniaturized energy harvesters, and the finding of robust piezoelectric response in a transmembrane protein also raises fundamental questions regarding the molecular evolution, activation, and role of regulatory proteins in the cellular nanomachinery, indicating that piezoelectricity might be important for fundamental physiological processes.     

Organic Synaptic Transistors: The Evolutionary Path from Memory Cells to the Application of Artificial Neural Networks

The progress of neural synaptic devices is experiencing an era of explosive growth. Given that the traditional storage system has yet to overcome the von Neumann bottleneck, it is critical to develop hardware with bioinspired information processing functions and lower power consumption. Transistors based on 2D materials, metal oxides, and organic materials have been adopted to mimic the synapse of a human brain, due to their high plasticity, parallel computing, integrated storage, and system information processing. Among these materials used to build transistors, organic semiconductors are considered to be the most promising candidate for neural synaptic devices and bio-electronics, owing to their easy processing, mechanical flexibility, low cost, good bio-compatibility, and ductility. This review focuses on the recent advances in organic synaptic devices with various structures, materials, and working mechanisms. The applications of artificial neural networks that integrate multiple organic synaptic transistors are also concretely discussed. Finally, the challenges that organic synaptic devices currently face are discussed and future developments are forecast.     

Photomemory and Pulse Monitoring Featured Solution-Processed Near-Infrared Graphene/Organic Phototransistor with Detectivity of 2.4 × 1013 Jones

Emerging graphene/organic phototransistors are eye-catching technologies owing to their unique merits including easy/low-cost fabrication, temperature independent, and achieving various functions. However, their development in the near-infrared (NIR) region is experiencing a bottleneck of inferior sensitivity due to low exciton dissociation efficiency and inefficient charge extraction rate. Here, a novel-design solution-processed graphene/organic NIR phototransistor is reported, that is, creatively introducing electron extraction layer of ZnO on graphene channel and employing organic ternary bulk heterojunction as photosensitive layer, successfully breaking that bottleneck. The phototransistor exhibits a high responsivity of 6.1 × 10⁶ A W⁻¹, a superior detectivity of 2.4 × 10¹³ Jones, and a remarkable minimum detection power of 1.75 nW cm⁻² under 850 nm radiation. Considering its excellent NIR detection performance, a noncontact transmission-type pulse monitoring is carried out with no external circuit support, from which human pulse signal and heart rate can be displayed in real time. The phototransistor, interestingly, can be switched into a photomemory function with a retention time of 1000 s in the atmosphere through a gate voltage of −20 V. The design takes the characteristics of graphene/organic phototransistors to a higher level, beyond the limit of sensitivity, and opens up a novel approach for developing multifunction devices.     

2D van der Waals Heterojunction of Organic and Inorganic Monolayers for High Responsivity Phototransistors

Van der Waals (vdW) heterostructures composing of organic molecules with inorganic 2D crystals open the door to fabricate various promising hybrid devices. Here, a fully ordered organic self-assembled monolayer (SAM) to construct hybrid organic–inorganic vdW heterojunction phototransistors for highly sensitive light detection is used. The heterojunctions, formed by layering MoS₂ monolayer crystals onto organic [12-(benzo[b]benzo[4,5]thieno[2,3-d]thiophen-2-yl)dodecyl)]phosphonic acid SAM, are characterized by Raman and photoluminescence spectroscopy as well as Kelvin probe force microscopy. Remarkably, this vdW heterojunction transistor exhibits a superior photoresponsivity of 475 A W⁻¹ and enhanced external quantum efficiency of 1.45 × 10⁵%, as well as an extremely low dark photocurrent in the pA range. This work demonstrates that hybridizing SAM with 2D materials can be a promising strategy for fabricating diversified optoelectronic devices with unique properties.     

OLED背光源技术研究进展

有机电致发光二极管(OLED)因其白光材料的多样性、制程的简单性和成本低廉性,特别是其面光源的属性,相较于电致发光二极管(LED)的点光源,更有望成为未来液晶显示器件背光源的主角。介绍了OLED背光源关键技术的最新进展,分别阐述了白光OLED发光效率的提升,OLED器件稳定性和寿命的提高,OLED制备的最新工艺,偏极化的OLED技术,OLED背光源与液晶显示面板匹配技术,还介绍OLED背光源产业发展及发展现状,并对OLED背光源技术的发展趋势进行了展望。     

三种不同状态下有机分子的光谱特性

研究了有机材料蒽和8-羟基喹啉铝(Alq3)在固态,溶解液态和镶嵌隔离态三种状态下的发光特性,发现随着有机分子密度的降低,即从高密度态向单体状态的变化过程中,其发光峰位出现蓝移,发光峰半高宽的宽度变窄,发光峰的对称性变好.