有机自旋阀及其磁电阻效应

随着巨磁电阻效应(GMR)的发现, 自旋电子学迅速兴起并成为一门新的学科。自旋电子学以电子的自旋属性为信息载体, 有望实现集逻辑、存储和通信于一体的多功能、低功耗器件, 为下一代电子学开辟新的路径。有机半导体具有低自旋轨道耦合、弱超精细相互作用和长自旋弛豫时间等特点, 因而受到了极大关注。有机自旋阀(OSVs)是研究有机材料中自旋注入和传输的原型器件。本文综述了有机自旋阀的发展历程, 总结了有机半导体的自旋弛豫机制, 详细分析了有机自旋阀中存在的关键科学问题, 如室温自旋传输的实现策略和磁电阻符号问题, 介绍了自旋有机发光二极管和自旋光伏器件等新型自旋器件, 最后对有机自旋电子学未来发展进行了展望。     

有机场效应晶体管和分子电子学研究进展

近几年来,有机场效应晶体管在材料和器件方面都取得了长足的进展,成为分子电子学的一个重要方向。本文从有机半导体材料设计、有机半导体器件的构筑、单分子电子器件和纳米管在电子器件中的应用等方面,简单综述了有机场效应晶体管和分子电子学的最新研究进展。     

表面限域效应下的区域选择性脱氢环化合成纳米石墨烯分子

<正>纳米石墨烯作为一类重要的有机半导体材料在分子电子学、自旋电子学和光电子学中有着广泛的应用前景~(1–3)。化学家利用设计的分子前驱体在溶液中自下而上地合成了众多具有不同尺寸和边界结构的纳米石墨烯分子~4,为精细调控纳米石墨烯的电学性质提供了途径。但是溶液法合成过     

可蒸镀自旋交叉配合物的薄膜与器件

自旋交叉配合物在温度、压力、光照和磁场等刺激下可以发生高低自旋态之间的可逆转变, 通常还伴随着颜色、体积和电导率变化以及热滞等效应, 因此这类材料在光热开关、传感器、显示和存储等领域具有潜在的应用. 由于可以获得高质量的超洁净薄膜, 高真空蒸镀工艺常用于分子电子学与分子磁学等的器件制备, 目前报道的可蒸镀自旋交叉配合物种类较少, 大大限制了自旋交叉配合物的器件应用. 针对可蒸镀自旋交叉配合物的薄膜与器件进行了系统的综述, 介绍了几种主要的适于高真空蒸镀的自旋交叉配合物, 结合不同的表征手段分析了衬底对分子薄膜自旋转变特性的影响, 并针对相关的概念性器件进行了讨论, 最后对自旋交叉配合物在器件应用中存在的难点和未来的发展趋势进行了展望和评述, 希望能够为自旋交叉领域的器件应用提供一些借鉴.     

有机微纳晶场效应晶体管

有机单晶中分子排列长程有序、无晶界且杂质和缺陷很少,是揭示有机半导体材料本征性能和制备高迁移率器件的最佳选择。因此,有机单晶材料对于构筑高性能电子器件和电路等方面具有无可比拟的优势。同时,有机单晶材料也为揭示半导体材料微观分子堆积与宏观电性能关系提供了重要手段。有机分子间以弱的范德华力相结合,因此,有机半导体单晶多以微纳晶形式存在。目前,种类繁多的有机微纳晶半导体材料被广泛应用于高性能场效应晶体管器件,这些器件的研究不仅可以筛选出高性能的有机半导体材料,也为科研人员提供更多的机会来理解有机半导体中电荷传输的物理内涵。本综述介绍了有机单晶场效应晶体管的基本结构和运行机理;微纳晶制备、表征方法以及器件构筑方法;总结了近三年来有机微纳晶半导体材料与器件取得的最新研究进展;探讨了当前有机微纳晶研究的热点和趋势并分析了面临的挑战。     

有机半导体材料中的电荷转移

在介绍有机半导体材料电荷转移基本理论的基础上,对利用电荷转移研究有机半导体材料的导电、光电导和发光过程的现状进行评述,认为电荷转移是有机半导体材料研究的关键问题,开展其研究不仅有助于弄清一些新现象、新效应的物理起因,还可望找到预测有机半导体材料相关性能的有效手段.     

有机半导体Terazulene单晶双极电荷传输性质的理论研究

利用密度泛函方法计算Terazulene单晶的重组能和分子间电子耦合,结合Marcus电荷转移速率理论以及随机行走技术模拟电荷迁移率,分别研究Terazulene单晶中电子与空穴的角分辨各向异性迁移率及平均迁移率.结果表明,Terazulene单晶具有均衡的电子与空穴传输性质,并分析了具体原因.由于p型有机半导体Naphthodithiophene(NDT)的分子共轭长度与Terazulene接近,通过比较Terazulene单晶和NDT单晶中电荷传输的差异,从理论上理解分子结构对有机半导体材料电荷传输性能的影响.     

并五苯分子电荷注入导致自旋极化的密度泛函理论研究

用密度泛函理论研究了不带自旋的空穴注入并五苯后体系的自旋相关特性. 电荷注入后并五苯分子中存在自发自旋极化行为. 当注入电荷量达一定程度,分子磁矩随注入电荷量的增加呈线性增长,最大磁矩可达1μB. 注入电荷和并五苯分子的相互作用导致分子体系结构发生变化,同时电荷密度分布及自旋密度分布也发生了变化. 注入电荷先填充自旋劈裂的碳原子pz轨道.     

手性有机光电功能材料及其圆偏振光发射与探测

手性有机半导体由于其新颖的性质引起了有机光电领域极大的研究兴趣. 将手性引入有机半导体材料不仅可以调控聚集态结构影响载流子输运进而影响光电器件的性能, 而且催生了圆偏振光直接发射与探测材料与器件的产生与发展. 手性材料与圆偏振光之间的相互作用使得其在3D显示、量子通讯、信息存储与处理等领域展示出广泛的应用前景. 本综述总结近年来手性有机光电材料及器件的研究进展, 主要围绕手性对有机半导体材料性质与器件性能的影响展开, 聚焦于手性有机半导体的圆偏振光直接发射与探测等研究, 旨在进一步为手性有机光电子领域的发展提供系统的认识.     

电极材料对NPB/Alq3有机电致发光器件性能的影响

采用不同材料作为有机电致发光器件(OELDs)的电极, 制备了基本结构为[阳极/NPB(40 nm)]/Alq3(50 nm)/阴极]的异质结双层器件, 并通过改变OELDs器件的阴极或阳极来研究电极材料对器件光电性能的影响. 研究结果表明, 各器件电流-电压(I-V)关系的基本特征与陷阱电荷限制电流(TCLC)机制的拟合情况相符. 由于有机材料本身能级的无序性以及载流子迁移率对温度和电场的依赖性, 不同电极的载流子注入能力与其功函数并无直接关系. 双层器件中由于空穴传输层的引入, 使得载流子复合区域位于有机层异质结界面处, 降低了金属阴极对激子的猝灭作用, 从而大大提高了器件性能. 此外, 金属电极OLEDs器件结构具有的微腔效应会导致发射光谱的位移和谱峰宽度变窄, 这表明通过对金属电极的表面改性和优化可使器件性能超过常规结构的器件.     

Substitutional doping of symmetrical small fullerene dimers

Magnetic carbon nano-structures have potential applications in the field of spintronics as they exhibit valuable magnetic properties. Symmetrically sized small fullerene dimers are substitutional doped with nitrogen (electron rich) and boron (electron deficient) atoms to visualize the effect on their magnetic properties. Interaction energies suggests that the resultant dimer structures are energetically favorable and hence can be formed experimentally. There is significant change in the total magnetic moment of dimers of the order of 0.5 μ_B after the substitution of C atoms with N and B, which can also be seen in the change of density of states. The HOMO-LUMO gaps of spin up and spin down electronic states have finite energy difference which confirm their magnetic behaviour, whereas for non-magnetic doped dimers, the HOMO-LUMO gaps for spin up and down states are degenerate. The optical properties show that the dimers behave as optical semiconductors and are useful in optoelectronic devices. The induced magnetism in these dimers makes them fascinating nanocarbon magnetic materials.     

面向有机光电材料的电子激发态结构与过程的计算方法

共轭聚合物与有机分子材料中的电子激发结构与过程决定了材料的光电功能：根据Kasha规则,低能级激发态的排序决定能否发光;最低激发态至基态的辐射跃迁与无辐射跃迁之间的竞争决定了发光效率,后者主要由非绝热耦合（声子作用）决定;电荷激发态载体的传输由电子分布与振动耦合或杂质和无序的散射弛豫过程决定．本文针对有机功能材料的发光性能,介绍两种理论方法的研究进展,即可用于计算共轭聚合物激发态结构的量子化学密度矩阵重整化群方法和计算发光效率的多模耦合无辐射跃迁速率方法．这些方法被应用于有机功能材料的性能预测和分子设计中．     

Spintronics and spintronics materials

The review concerns the fundamentals of spintronics (spin-transport electronics). The material covers spin-spin interactions and spin relaxation in semiconductors as well as spin and spin injection related effects in the condensed matter. Examples of promising spintronic devices are given, requirements for spintronic materials are formulated, methods of synthesis of spintronic materials are described, and the physicochemical properties of some materials are characterized. Organic spintronic materials are briefly outlined and the state-of-the art in the field of research on inhomogeneous magnetic semiconducting materials possessing high-temperature ferromagnetism is described. The emphasis is placed on the chemical bonding and electronic structure of magnetic impurities in semiconductors, consideration of the nature of ferromagnetism, and on the character of exchange interactions between localized spins in novel spintronic materials.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2255–2303, November, 2004.     

Synthesis and Application of Rylene Imide Dyes as Organic Semiconducting Materials

Rylene imide dyes have been among the most promising organic semiconducting materials for several years due to their remarkable optoelectronic properties and high chemical/thermal stability. In the past decades, various excellent rylene imide dyes have been developed for optoelectronic devices, such as organic solar cells (OSCs) and organic field‐effect transistors (OFETs). Recently, tremendous progress of perylene diimides (PDIs) and their analogues for use in OSCs has been achieved, which can be attributed to their ease of functionalization. In this review, we will mainly focus on the synthetic strategies toward to latest PDI dyes and higher rylene imide analogues. A variety of compounds synthesized from different building blocks are summarized, and some properties and applications are discussed.     

Organic Fluorophores Exhibiting Highly Efficient Photoluminescence in the Solid State

There has been extensive research on the development of organic optoelectronic devices, such as organic light‐emitting diodes, organic field‐effect transistors, and organic solid‐state lasers from various viewpoints, ranging from basic studies to practical applications. As organic materials are used as solids in these devices, the importance of organic chromophores that exhibit intense emissions of visible light in the solid state is greatly increasing in the field of organic electronics. However, highly efficient emission from organic solids is very difficult to attain because most organic emitting materials strongly tend to cause concentration quenching of the luminescence in the condensed phase. Therefore, in order to generate and improve organic optoelectronic devices, it is necessary to design novel chromophores that exhibit superior solid‐state emission performance. This Focus Review covers the recent development of highly emissive organic small molecules whose photoluminescence quantum yields in the solid state have been reported. Following the introduction, the photophysical processes of excited molecules are briefly reviewed. Subsequently, organic solid fluorophores are described with an emphasis on the characteristics of their molecular structures.     

Overcoming excitonic bottleneck in organic solar cells: electronic structure and spectra of novel semiconducting donor-acceptor block copolymers

A novel class of organic semiconductors aimed at improving the efficiency of organic photovoltaic devices is investigated by an ab initio electronic structure theory. Two conjugated block copolymers composed of chemically bound donor and acceptor blocks show substantial charge transfer upon photoexcitation, suggesting that the optically excited states are separated charge pairs rather than strongly interacting charges forming excitons. In contrast, little charge transfer is seen in the ground electronic state. The optical cross-sections of the charge separated states are quite high due to a good overlap of the tails of the ground and excited state wavefunctions. The absorption spectra of the systems cover visible spectrum and extend to the infrared, suggesting good prospects for light harvesting. The calculation results indicate that the proposed class of semiconducting molecular heterojunctions may overcome the exciton bottleneck problem in organic photovoltaic materials.     

Organometallic chemistry related to applications for microelectronics in Japan

This is meant to be a brief overview of the developments of research activities in Japan on organometallic compounds related to their use in electronic and optoelectronic devices. The importance of organometallic compounds in the deposition of metal and semiconductor films for the fabrication of many electronic and opto-electronic devices cannot be exaggerated. Their scope has now extended to thin-film electronic ceramics and high-temperature oxide superconductors. A variety of organometallic compounds have been used as source materials in many types of processing procedures, such as metal–organic chemical vapor deposition (MOCVD), metalorganic vapor-phase epitaxy (MOVPE), metal–organic molecular-beam epitaxy (MOMBE), etc. Deposited materials include silicon, Group III–V and II–VI compound semiconductors, metals, superconducting oxides and other inorganic materials. Organometallic compounds are utilized as such in many electronic and optoelectronic devices; examples are conducting and semiconducting materials, photovoltaic, photochromic, electrochromic and nonlinear optical materials. This review consists of two parts: (I) research related to the fabrication of semiconductor, metal and inorganic materials; and (II) research related to the direct use of organometallic materials and basic fundamental research.     

A First-Principles Study of C3N Nanostructures: Control and Engineering of the Electronic and Magnetic Properties of Nanosheets,Tubes and Ribbons

Using first-principles calculations we systematically investigate the atomic, electronic and magnetic properties of novel two-dimensional materials (2DM) with a stoichiometry C₃N which has recently been synthesized. We investigate how the number of layers affect the electronic properties by considering monolayer, bilayer and trilayer structures, with different stacking of the layers. We find that a transition from semiconducting to metallic character occurs which could offer potential applications in future nanoelectronic devices. We also study the affect of width of C₃N nanoribbons, as well as the radius and length of C₃N nanotubes, on the atomic, electronic and magnetic properties. Our results show that these properties can be modified depending on these dimensions, and depend markedly on the nature of the edge states. Functionalization of the nanostructures by the adsorption of H adatoms is found induce metallic, half-metallic, semiconducting and ferromagnetic behavior, which offers an approach to tailor the properties, as can the application of strain. Our calculations give insight into this new family of C₃N nanostructures, which reveal unusual electronic and magnetic properties, and may have great potential in applications such as sensors, electronics and optoelectronic at the nanoscale.     

并五苯及其衍生物在有机场效应晶体管中的应用

有机场效应晶体管（organic field—effect transistors,OFETs）是以有机半导体材料作为有源层,通过电场控制电流的电子器件．与传统的无机半导体器件相比,由于其可应用于生产大面积、柔性、低成本电子设备而备受关注,在有机存储器件、有机太阳能电池、柔性平板显示和电子纸等众多领域具有潜在而广泛的应用前景．并苯类材料因其紧密的分子堆积及优异的半导体性能被广泛研究．其中,并五苯及其衍生物在场效应晶体管中表现出良好的性质,其效果甚至可以与非晶硅相媲美,但并五苯较差的溶解性及环境稳定性阻碍了其进一步应用．科研工作者通过对分子结构进行修饰改造设计,合成了一系列并五苯的衍生物,其不仅在稳定性、电学性能和溶解性方面有很大提高,还可以将该p-型半导体材料拓展到双极性及n-型半导体材料领域．本文对并五苯及其衍生物在有机场效应晶体管中的应用进行了较为全面的综述,期望对该领域的研究起到一定的推动作用．