退火对聚合物有机发光器件的影响

制作了结构为ITO／MEH—PPV／AI的单层聚合物有机发光器件(PLED),在镀铝电极前后分别对器件进行高于MEH—PPV玻璃化温度的退火处理。结果表明,镀铝电极后的退火处理可使器件的效率提高30％左右,器件的寿命增加40％左右;而镀铝电极前的退火处理对器件影响不大。     

Controllable π junction in a Josephson quantum-dot device with molecular spin

We consider a model for a single molecule with a large frozen spin sandwiched in between two BCS superconductors at equilibrium, and show that this system has a π junction behavior at low temperature. The π shift can be reversed by varying the other parameters of the system, e.g., temperature or the position of the quantum dot level, implying a controllable π junction with novel application as a Josephson current switch. We show that the mechanism leading to the π shift can be explained simply in terms of the contributions of the Andreev bound states and of the continuum of states above the superconducting gap. The free energy for certain configuration of parameters shows a bistable nature, which is a necessary pre-condition for achievement of a qubit.     

Shot noise in a quantum dot coupled to carbon nanotube terminals applied with a microwave field

We have investigated the spectral density of shot noise for the system of a quantum dot (QD) coupled to two single-wall carbon nanotube terminals irradiated with a microwave field on the QD. The terminal features are involved in the shot noise through modifying the self-energy of QD. The contributions of carbon nanotube terminals to the shot noise exhibit obvious behaviors. The novel side peaks are associated with the photon absorption and emission procedure accompanying the suppression of shot noise. The shot noise in balanced absorption belongs to sub-Poissonian, and it is symmetric with respect to the gate voltage. The differential shot noise displays intimate relation with the nature of carbon nanotubes and the applied microwave field. It exhibits asymmetric behavior for the unbalanced absorption case versus gate voltage. The Fano factor of the system exhibits the deviation of shot noise from the Schottky formula, and the structures of terminals obviously contribute to it. The super-Poissonian and sub-Poissonian shot noise can be achieved in the unbalanced absorption in different regime of source-drain bias.     

Second- and third-harmonic generations for a nondilute suspension of coated particles with radial dielectric anisotropy

We derive expressions for the effective nonlinear susceptibility tensors for both the second harmonic generation (SHG) and induced third harmonic generation (THG) of nonlinear composite materials, in which nondilute coated particles with radial dielectric anisotropy are randomly embedded in the linear host. Two types of coated particles are considered. The first is that the core possesses a second order nonlinear susceptibility and the shell is linear and radially anisotropic, while the second is that the core is linear with radial anisotropy and the shell has a second order nonlinear susceptibility. We observe greatly enhanced SHG and THG susceptibilities at several surface plasmon resonant frequencies. For the second model, due to the coating material being metallic, there exists two fundamental resonant frequencies ω_c1 and ω_c2, whose difference ω_c2-ω_c1 is strongly dependent on the interfacial parameter and the radial dielectric anisotropy. Furthermore, in both systems, the adjustment of the dielectric anisotropy results in larger enhancement of both SHG and induced THG susceptibilities at surface plasmon resonant frequencies than the corresponding isotropic systems. Therefore, both the core-shell structure and the dielectric anisotropy play important roles in determining the nonlinear enhancement and the surface resonant frequencies.     

High Tc Superconducting Materials for Strong Current Applications： Approach at the First Stage

Strong current and large-scale application is the most important prospect of high Te superconductors （HTS）. Practical HTS samples in various forms have been produced with high critical currents operated at economic cryogenic temperatures. Engineering applications of those HTS materials have been studied with various HTS prototype devices. The applicable HTS materials produced in different forms are verified in this paper with regard to their strong current characterizations, and the HTS applications are summarized along with the HTS prototypes made.     

一种背栅极冷阴极器件中纳米线表面电场的分析

利用静电场理论计算了背栅极冷阴极器件的纳米线附近电场,给出电场分布的表示式及J-V曲线,并分析了几何参数对纳米线顶端表面电场的影响.结果表明,纳米线顶端表面产生巨大的电场,随着离纳米线顶端表面距离的增大,电场迅速下降;纳米线突出栅孔的长度(L-d1)越大,纳米线半径r0、栅孔半径R以及栅极与阳极间距d2越小,则纳米线顶端表面电场越强,而d2较大时d2对表面电场的影响很弱;纳米线顶端边缘电流密度J随着阳极与栅极电压的增加而指数增大.     

An Object Oriented Architectural Library for the Design and Implementation of Network Protocols

The society of telecommunication and computer networks encompasses a wide variety of organizations, forums and industry companies that specify, standardize, evaluate, implement and deploy network infrastructures. These infrastructures are well defined and deployed in order to offer high quality end-user services and meet the need for interconnectivity, expandability and upgradeability. What users see and experience is the tip of the iceberg. Great amount of time and money is spent in specification, standardization, design, debugging, testing (both conformance and stress) and finally evaluating network components or subsystems before the deployment takes place. The framework, proposed in the current paper and implemented in open source software library, provides an object oriented methodology for the implementation of network protocols and the software realization of network components. The method is formed in respect to: (a) operating system architecture (b) network architecture and (c) Object Oriented (OO) methodology.     

有机发光显示技术的进展

有机发光显示被认为是下一代最理想的显示技术,具有自主发光、功耗小、视角宽、成本低和响应速度快等优点。本文在简述有机电致发光器件的电极结构和发光材料的基础上,重点介绍了有机显示器件的驱动技术和面板的研发成果,并展望未来发展的前景。     

Band‐Offset Engineering for Enhanced Open‐Circuit Voltage in Polymer–Oxide Hybrid Solar Cells

The power conversion efficiency of organic and hybrid solar cells is commonly reduced by a low open‐circuit voltage (V_OC). In these cases, the V_OC is significantly less than the energy of the lowest energy absorbed photon, divided by the elementary charge q. The low photovoltage originates from characteristically large band offsets between the electron donor and acceptor species. Here a simple method is reported to systematically tune the band offset in a π‐conjugated polymer–metal oxide hybrid donor–acceptor system in order to maximize the V_OC. It is demonstrated that substitution of magnesium into a zinc oxide acceptor (ZnMgO) reduces the band offset and results in a substantial increase in the V_OC of poly(3‐hexylthiophene) (P3HT)–ZnMgO planar devices. The V_OC is seen to increase from 500 mV at x = 0 up to values in excess of 900 mV for x = 0.35. A concomitant increase in overall device efficiency is seen as x is increased from 0 to 0.25, with a maximum power‐conversion efficiency of 0.5 % obtained at x = 0.25, beyond which the efficiency decreases because of increased series resistance in the device. This work provides a new tool for understanding the role of the donor–acceptor band offset in hybrid photovoltaics and for maximizing the photovoltage and power‐conversion efficiency in such devices.