Very Large Photoconduction Enhancement Upon Self‐Assembly of a New Triindole Derivative in Solution‐Processed Films

A new carbazole‐related small molecule exhibiting self‐assembly into ordered nanostructures in solution‐processed cast films has been synthesized and its charge‐photogeneration and ‐transport properties have been investigated. Large photoconductivity was measured in the amorphous state while an enormous improvement in the photoconduction properties was observed when the molecules spontaneously organized. Photocurrents increased upon self‐assembly by up to four orders of magnitude, mostly due to the drastic enhancement of the charge photogeneration. A greatly favorable arrangement of the aromatic cores in the resulting nanostructures, which were characterized by X‐ray analysis, may explain these improvements. Photocurrents of mA cm^?2, on/off ratios of 10⁴ and quantum efficiencies of unity at low field and light intensity, which are among the best values reported to date, along with the simplicity of fabrication, give this readily‐available organic system great potential for use in plastic optoelectronic devices.     

Very Low Degree of Energetic Disorder as the Origin of High Mobility in an n‐channel Polymer Semiconductor

Charge transport is investigated in high‐mobility n‐channel organic field‐effect transistors (OFETs) based on poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2), Polyera ActivInk? N2200) with variable‐temperature electrical measurements and charge‐modulation spectroscopy. Results indicate an unusually uniform energetic landscape of sites for charge‐carrier transport along the channel of the transistor as the main reason for the observed high‐electron mobility. Consistent with a lateral field‐independent transport at temperatures down to 10 K, the reorganization energy is proposed to play an important role in determining the activation energy for the mobility. Quantum chemical calculations, which show an efficient electronic coupling between adjacent units and a reorganization energy of a few hundred meV, are consistent with these findings.     

On the Origin of Green Emission Bands in Fluorene‐Based Conjugated Polymers

Blue‐light‐emitting diodes made of polyfluorenes have low stability and, under operation, rapidly degrade and produce undesirable low‐energy emission bands (green or g‐bands). A spectroelectrochemical study of the degradation process suffered by polyfluorenes is reported here. These polymers lose their electronic properties by electrochemical oxidation and reduction through σ‐bond breaking. In addition, upon electrochemical reduction, the development of a structured green emission band at 485 nm is observed. The position and shape of this band is different from the usual featureless band at 535 nm assigned to fluorenone defects. The green‐light‐emitting product is isolated and analyzed by Fourier‐transform IR spectroscopy; fluorenone formation is excluded. The isolated product is crosslinked; its green emission is probably related to the formation of an intramolecular excimer.     

Towards neuromorphic electronics: Memristors on foldable silicon fabric

The advantages associated with neuromorphic computation are rich areas of complex research. We address the fabrication challenge of building neuromorphic devices on structurally foldable platform with high integration density. We present a CMOS compatible fabrication process to demonstrate for the first time memristive devices fabricated on bulk monocrystalline silicon (100) which is next transformed into a flexible thin sheet of silicon fabric with all the pre-fabricated devices. This process preserves the ultra-high integration density advantage unachievable on other flexible substrates. In addition, the memristive devices are of the size of a motor neuron and the flexible/folded architectural form factor is critical to match brain cortex׳s folded pattern for ultra-compact design.     

模拟电子技术课程项目化教学改革探讨

在传统的模拟电子技术教学中,存在电子元件非线性、电子电路比较复杂、理论知识抽象繁琐、学生学习兴趣低且动手能力差等特点。在这种教学条件下,构建模拟电子技术的项目理实一体化教学,将理论知识寓于实际项目中,实现让学生在动手做实际电子产品中学会模拟电子技术的基础知识,提升动手能力,有利于真正实现高职院校应用型技能型人才的培养目标。     

基于决策表的印刷电路板测试诊断过程优化

针对传统的决策树生成算法之不足,提出了两种改进算法。用实例说明改进处法具有更好的优化效果,且证明了传统算法是改进算法Ⅱ的特例。基于决策表和决策树,构造了电路板故障诊断专家系统,实现了印刷电路板测试诊断过程优化,使故障诊断的平均测试开销最小。     

纳米电子技术

微电子技术引发了本世纪的信息革命。纳米科学技术将成为二十一世纪信息时代的核心和国际科学界和工程技术界关注的热点。     

Impact of power electronics packaging on the reliability of grid connected photovoltaic converters for outdoor applications

This paper deals with thermal and reliability aspects of converters for grid connected photovoltaic applications (rate power approximately 100 W) which can be integrated into solar modules. The use of these Module Integrated Converters (MIC) promises a reduction of costs due to mass production. It improves behaviour of the whole photovoltaic system, as there is no voltage mismatch caused by shading effects. The electronic components of the MIC are exposed to extreme environmental conditions. Lifetime limiting factors are described. Methods to increase the lifetime of the most crucial components in the MIC, electrolytic capacitors, are described. The presented 1st generation Low Profile MIC with “optimised design” is capable of running in very high ambient temperatures. This design maximises availability of the photovoltaic system, which consequently leads to a cost reduction of the electrical energy delivered to the grid. Different realisations of how to integrate the designed Low Profile MIC into the solar module are discussed. A detailed thermal simulation is used to optimise the MIC design according to temperature and reliability issues. The models used for thermal simulation are described.     

多孔侧肋双层微通道热沉构形优化

建立了多孔侧肋双层微通道复合热沉模型,选取最大热阻最小化为优化目标、热沉单元端面纵横比为优化变量,在热沉总体积和流体区域体积占比给定的条件下,对复合热沉进行了构形优化,并分析了冷却剂入口速度、多孔材料孔隙率、上下通道高度比、流体区域体积占比、肋厚比等参数对热沉最优构形的影响.结果表明:给定初始条件,优化热沉单元端面纵横比,可使最大热阻减小21.19％;在热沉单元端面纵横比较小时,减小孔隙率有利于降低最大热阻,而在热沉单元端面纵横比较大时,存在最优的孔隙率使得最大热阻最小;上下通道高度比和肋厚比的改变均未影响热沉最优构形.