Nondoped blue fluorescent OLED based on cyanophenanthrimidazole‐styryl‐triphenylamine/carbazole materials

New 2‐(4′‐9H‐carbazole‐9‐yl)‐styryl‐1H‐phenathro[9,10‐d]imidazole‐1‐yl)benzonitrile (SPICN‐Cz) and 4‐(2‐(4‐(diphenylamino)phenyl‐styryl‐1H‐phenathro[9,10‐d]imidazole‐1‐yl)benzonitrile (SPICN‐TPA) have been synthesised, and their photophysical, electrochemical, and electroluminescent properties were analysed in comparison with their cyano‐free parent compounds, SPI‐Cz, and SPI‐TPA. Solvatochromic effects show the transformation of an excited state character from locally excited (LE) state to charge transfer (CT) state. Using time‐dependent density functional theory calculation, the excited state properties of these donor‐acceptor blue emissive materials have been analysed. Their excited state properties have been tuned by replacing the strong donor triphenylamine to weak donor carbazole to achieve the combination of high photoluminance efficiency locally excited (LE) component and high exciton‐utilizing CT component in one excited state. Hybridization processes between LE and CT components of SPICN‐Cz and SPICN‐TPA in the emissive state have been discussed. The nondoped organic light emitting diode device based on SPICN‐Cz exhibit better electroluminescent performances than those of SPICN‐TPA–based device: high external quantum efficiency of 2.58 %, current efficiency of 2.90 cd A^‐1, and power efficiency of 2.26 lm W^‐1 with Commission Internationale de l'Éclairage (CIE) coordinates of (0.15, 0.12). The excited state modulation and the composition of LE and CT states in the donor‐acceptor system could be useful to design low‐cost, high‐efficiency fluorescent organic light emitting diode materials.     

阳极界面修饰对钙钛矿太阳能电池性能的影响

采用在聚(3,4-乙撑二氧噻吩)∶聚苯乙烯磺酸(Poly(3,4-ethylenedioxythiophene)∶Poly(styrenesulfonate),PEDOT∶PSS)阳极界面层上直接旋涂二甲基亚砜(Dimethyl Sulfoxide,DMSO)的方法,对PEDOT∶PSS薄膜进行修饰,以提高所制得的钙钛矿太阳能电池器件性能.在5000rpm转速条件下旋涂DMSO后,器件的能量转换效率达到11.43%,与PEDOT∶PSS阳极界面层未做任何修饰的器件相比,效率提高了29.15%.测试表征了修饰前后PEDOT∶PSS薄膜的透光性、表面形貌、电导率、器件的外量子效率曲线以及器件在光照和暗态下的J-V特性曲线,分析了器件性能提高的原因.结果表明:经过修饰的PEDOT∶PSS薄膜导电性显著增强,从而更加有利于器件阳极对空穴的抽取和收集;较未修饰时,器件的短路电流密度得到了大幅度提升,进而使得器件获得更高的能量转换效率.     

高衍射效率衍射望远镜系统的设计/加工及成像性能测试

为提高衍射效率,设计并制作了口径为300mm的衍射成像系统.该系统的物镜是由一块四台阶位相型菲涅尔波带片通过激光直写套刻和Ar离子束物理刻蚀技术在石英玻璃基板上加工而成.测试了衍射物镜的衍射效率,实验结果表明:衍射物镜在波长632.8nm处的衍射效率为66.4%,达到理论值的82%.搭建了衍射成像系统光路,分别采用10μm星点孔与分辨率板,测试了系统的成像性能.实验测得星点像直径为44μm,分辨率板的极限分辨率达到84lp/mm,接近该系统的理论计算值,表明该衍射成像系统具有较好的成像性能.     

高灵敏度区域中子监测仪探测效率曲线模拟

中子监测仪对不同能量中子的探测效率是其重要的性能指标,直接影响其测量值的可信度与使用效果。针对中国科学院高能物理研究所生产的高灵敏度区域中子监测仪（HANM型）,利用蒙特卡罗软件模拟其探测效率曲线,模拟结果表明该仪器探测效率随能量增加,先上升后下降,其探测效率最高值在1 MeV附近。通过改变模拟条件中的射线入射方向,对比探测效率曲线趋势变化,验证该型仪器的探测效率曲线趋势的可靠性。在此基础上,分别利用D-D,D-T加速器产生2.5 MeV和14 MeV单能中子,对探测效率曲线进行校准与验证,最终获得此型仪器的探测效率曲线。     

Two-stage electrostatic precipitator with co- and counter-flow particle prechargers

Lab-scale, two-stage electrostatic precipitation system comprising of precharging stage, in which PM2.5 particles are electrically charged, and collection stage, in which the charged particles are removed from the flowing gas by electric field, was investigated in this paper. Two types of electrostatic particle prechargers were compared with respect to the collection efficiency of the system: (1) co-flow precharger, in which ionic current was generated co-currently with the gas conveying the particles, and (2) counter-flow precharger, in which ionic current was generated oppositely to the flowing gas. In each case, the electrodes of precharger were supplied with DC or AC high-voltage in order to compare the effect of discharge mode on the collection efficiency of two-stage electrostatic precipitator. The collection stage was formed by two parallel-plate electrodes connected to DC high voltage source. Plate electrodes without discharge points (spikes) are corona-free electrodes, which prevent the collection stage from electrical discharges, and reduce the probability of back discharge ignition. The back discharge decreases collection efficiency of conventional electrostatic precipitators.It was concluded that the co-flow electrode configuration of the precharger, supplied with DC high voltage, has the highest total number collection efficiency for PM2.5 particles, higher than 95% and the mass collection efficiency larger than 99%. The counter-flow precharger provided only about 90% number collection efficiency of two-stage electrostatic precipitator. It was also shown that by AC electrode excitation, the collection efficiency of the system is lower than for DC supply. The two-stage electrostatic precipitators allowed obtaining higher fractional collection efficiency for PM2.5 particles than other conventional systems and can be recommended as highly effective devices for gas cleaning in power plants or cement industry.     

基于休眠机理的三维小基站蜂窝网络能效优化

小基站通常部署在写字楼、商贸区等城市密集区域以弥补传统宏基站在覆盖和传输方面的不足.小基站的分布一般是根据高峰时的网络负荷设计的,这必然导致网络负荷较低时的资源浪费.讨论了在平均接入率和信道容量双重约束下基于休眠机理的三维小基站蜂窝网络的能效优化问题.借助泊松点过程理论推导了三维小基站网络下行信道容量和平均接入率的数学表达式.通过分析下行信道容量和平均接入率的单调性得出同时满足传输信道容量和接入率要求的最佳休眠概率.分析了小基站最大用户连接数的最佳值,通过对该参数的合理配置,可以在满足通信指标的前提下最大程度地降低网络能耗.仿真结果表明,设计的基站休眠机理可以使小基站网络的能耗下降约21%.     

Numerical analysis of a dual-pass pumping laser with weak absorption

A model for a laser with dual-pass pumping is established, and an equation expressing the mode matching for this structure is presented. Through the numerical analysis of this equation, under the conditions of weak-absorption and effective absorption efficiency, the optimum radius of the pump beam waist as well as the optimum location is fitted to simple formulas, considering the quality of the pump beam, absorption coefficient, and beam waist of the cavity mode.Using these formulas, the laser with dual-pass pumping could be optimized to obtain a high slope efficiency. To test the utility of this model, an Nd:YVO_4 laser with dual-pass pumping and weak-absorption was built and optimized according to the results of the calculation. A good agreement between the results of the calculations and the experiment verified the model and the numerical analysis.     

Improvement of real time diffraction efficiency of NGD holograms by introducing electron donors

Nongelatin dichromated holographic film(NGD) is a new holographic recordingmaterial.Holograms recorded on this material have better environmental stability, higherdiffraction efficiency and stronger real time effect, etc..An experimental study to ascertainthe influence of two electron donors, namely,N,N-dimethylformamide(DMF) and dimethyl-sulfoxide(DMSO),on the real time diffraction efficiency(RTDE) of NGD holograms is car-ried out.The pressence of electron donors not only improves the sensitivity,but also enhancesthe real time effect greatly.RTDE of above 60% at±1 orders of NGD plane transimissiongrating is achieved by introducing electron donors.     

计算凹面闪耀光栅衍射效率的通用方法

为使凹面光栅的衍射能量更多地集中在所需要的级次上,提出了利用机械刻划的方法在凹面基底上制作变刻槽角度的凹面闪耀光栅,并利用菲涅耳-基尔霍夫衍射公式推导了同时在主截面和非主截面内计算凹面闪耀光栅衍射效率的理论方法,弥补了以往只在主截面内考虑衍射效率的不足,最后利用Matlab仿真软件模拟了衍射效率随波长的变化曲线,并对比了在不同制作和使用参数下衍射效率峰值的变化规律,为今后凹面光栅的设计和制作提供了参考价值。     

锂玻璃探测器中子探测效率的刻度

为了精确测量keV能区的中子俘获截面,中国原子能科学研究院正在建造一台4π 全吸收型γ 探测装置---GTAF,锂玻璃探测器将会作为中子束流监视器测量中子能谱。利用5SDH-2 加速器刻度了锂玻璃探测器在两个入射中子单能点(250 和565 keV) 的探测效率,并使用EANT4 和MCNP 程序模拟计算了锂玻璃探测器的相对探测效率。通过归一化实验数据和模拟结果,得到了锂玻璃探测器在10keV~1 MeV 能区的中子探测效率曲线。对于把锂玻璃探测器测量得到的飞行时间谱转化为中子束流能谱,是一项非常重要的工作,同时为探测器效率刻度提供了新方法。In order to accurately measure the neutron capture cross section in the energy range of keVMeV, 4 πgamma-ray total absorption facility (GTAF) is being constructed at China Institute of Atomic Energy (CIAE). The lithium glass detector will be used as a neutron beam monitor for GTAF. The detection efficiency of the lithium glass detector at two incident neutron energy points (250, 565 keV) was calibrated in 5SDH-2 accelerator, and the relative detection efficiency was simulated by GEANT4 and MCNP code. By the normalization of the experimental data and simulation result, the neutron detection efficiency curve of the lithium glass detector between 10 keV and 1 MeV was obtained. This work will be important to convert the Time-of-flight spectrum that be measured by Li-glass detector to the energy spectrum of neutron beam, and provide the new method for calibration of detection efficiency.