高荧光量子效率的分子分散型聚芴衍生物的放大自发发射特性

通过将掺杂剂单元用化学键接到聚芴的侧链上,实现了掺杂剂单元在高分子主体中的分子水平分散,开发了一种新型的基于掺杂剂/主体材料体系的分子分散型蓝光聚芴衍生物.与纯聚芴相比,这种新的分子分散型蓝光聚芴衍生物具有很高的荧光量子效率.以这种新的分子分散型蓝光聚芴衍生物为增益介质的激光器件,在Nd:YAG 355 nm脉冲激光泵浦下,获得了较好的放大自发发射光谱,阈值达到0.25 m J/(pulse cm2).从光物理的角度对薄膜的光学增益和光学损耗进行了定量运算和分析,经过拟合发现,当泵浦能量为0.06m J/pulse时,该聚芴衍生物增益系数可达23.08 cm-1,损耗系数为6.96 cm-1.优良的放大自发发射特性表明该聚芴衍生物是非常好的有机激光增益介质材料.     

Synthesis and photovoltaic properties of main chain polymeric metal complexes containing 1,10‐phenanthroline metal complexes conjugating alkyl fluorene or alkoxy benzene by C═C bridge for dye‐sensitized solar cells

Four main chain polymeric metal complexes (P1–P4) based on 1,10‐phenanthroline metal complexes via the Heck coupling have been synthesized and characterized by Fourier transform infrared spectroscopy, ¹H NMR, UV–Vis absorption, photoluminescence spectroscopy, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, elemental analysis, and cyclic voltammetry. To investigate their photovoltaic properties, the dye‐sensitized solar cells based on these polymers dyes are studied, under the illumination of AM 1.5G, 100 mW/cm². The study results show the four polymers exhibit good thermally stable and the solar cells based on them have good device performance, and the maximum power conversion efficiency is up to 0.735% for the solar cells based on P3 with a short‐circuit current (J_sc) of 1.68 mA/cm² and an open‐circuit voltage (V_oc) of 0.62 V. Copyright © 2012 John Wiley & Sons, Ltd.     

Compare study between smoothing efficiencies of epicyclic motion and orbital motion

The smoothing efficiencies of epicyclic motion and orbital motion in CCOS (computer controlled optical surfacing) were compared. CCOS polishing can smooth out mid-to-high spatial frequency errors which are smaller than tool size on optical mirrors due to the rigidity of polishing tools. The smoothing efficiencies of epicyclic motion and orbital motion with pitch lap and RC lap were compared and the result proved pitch lap with epicyclic motion smoothed ∼1.6 times faster than pitch lap with orbital motion while RC lap with epicyclic motion smoothed ∼1.85 times faster than RC lap with orbital motion.     

KClO_4/Zr在石英管内的燃烧发射光谱与燃烧产物分析

为了研究燃烧条件对KClO_4/Zr烟火剂燃烧过程中光辐射性能的影响,考察了KClO_4/Zr在开放环境和不同规格封闭石英管内的燃烧发射光谱和燃烧产物。借助光纤光谱仪、光电二极管和示波器测试了烟火剂燃烧过程中的光辐射能量分布和闪光时间-强度曲线,分析了所得发射光谱在(590±10),(750±10)和(808±10)nm三个主吸收波段内的光谱效率,借助SEM表征了不同燃烧条件下KClO_4/Zr燃烧产物的形貌。结果表明:在开放条件下燃烧时,KClO_4/Zr的燃烧发射光谱在可见光到近红外的宽波段内,最强辐射出现在730~820nm波段。在石英管内封闭燃烧时,随着石英管体积的减少,在石英管外检测到的燃烧发射光谱强度逐渐减弱,光谱能量分布也呈现不同的变化规律,而且对火焰发射光谱分布进行处理后,随着石英管体积的变化,得到(590±10),(750±10)和(808±10)nm波段的光谱效率也呈现不同的变化规律。但是,随着石英管体积的减少,KClO_4/Zr烟火剂的爆燃闪光辐射时间逐渐缩短,峰值辐射强度逐渐提高。增加石英管的直径,有利于在管外获得更高的有效光辐射能量,减少石英管的直径,则有利于提高烟火剂的峰值辐射强度。随着管直径的增大,KClO_4燃烧更加充分,产物粒径较小,呈规则的球状。而管长度的改变对反应并无太大影响。     

Is the US stock market becoming weakly efficient over time? Evidence from 80-year-long data

We propose a degree of market efficiency in terms of entropy concepts. The relative efficiency for the US stock market varies over time from 1929 to 2012, with a slight decline in the past 10 years.     

Improved efficiency of organic solar cells with modified hole‐extraction layers

The aim of this work has been to study the influence of modified hole‐extraction layers on the performance of organic solar cells (OSCs) based on blends of poly (3‐hexylthiophene) and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester. The hole‐extraction layers consist of poly (3,4‐ethylene dioxythiophene):polystyrene sulfonic acid (PEDOT:PSS) doped with different concentrations of bromine. Compared with pristine OSC without adding bromine to the hole‐extraction layer, the bromine‐doped OSCs show a 49% increase in the power conversion efficiency (from 2.12 to 3.16%), which could be attributed to the increase of electrical and optical properties of PEDOT:PSS films after the addition of bromine. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 50: 125–128, 2012     

InGaN/GaN多量子阱LED载流子泄漏与温度关系研究

通过测量光电流,直接观察了InGaN/GaN量子阱中载流子的泄漏程度随温度升高的变化关系。当LED温度从300K升高到360K时,在相同的光照强度下,LED的光电流增大,说明在温度上升之后,载流子从量子阱中逃逸的数目更多,即载流子泄漏比例增大。同时,光电流的增大在激发密度较低的时候更为明显,而且光电流随温度的增加幅度与激发光子的能量有关。用量子阱-量子点复合模型能很好地解释所观察到的实验现象。实验结果直接证明,随着温度的升高,InGaN/GaN量子阱中的载流子泄漏将显著增加,而且在低激发密度下这一效应更为明显。温度升高导致的载流子泄漏增多是InGaN多量子阱LED发光效率随温度升高而降低的重要原因。     

Naphthodithiophene-based donor materials for solution processed organic solar cells

As an emerging donor building block, naphthodithiophene (NDT) is causing more concerns in the field of organic semiconductors. With the rigid and coplanar molecule structure, NDT will exhibit more application space relying on its own advantage for facilitating the charge carrier transport. In this review article, we have summarized the development progress on the NDT-based donor materials for solution processed organic solar cells. Discussions and comments on those representative NDT type materials about structure and property are also presented.     

Exploring the electro‐optical properties of conjugated polymers based on oligo‐selenophene and oligo(3,4‐ethylenedioxyselenophene)

For seeking high‐efficiency narrow‐band‐gap donor materials to enhance short‐circuit current density for organic solar cells, a series of oligo‐selenophene (OS) and oligo(3,4‐ethylenedioxyselenophene) (OEDOS) with various chain lengths were designed and characterized using density functional theory (DFT) and time‐dependent DFT calculations. Based on the results, it can be seen that with increasing chain length of the oligomers in both syn‐ and anti‐adding manners, the bond length alternation is decreased which indicates that the π‐electron delocalization is increased. Also, when the chain length is increased the electronic energy gap and the optical energy gap are decreased. It can be concluded that the syn‐(OS)_n=10,14,15, anti‐(OS)_n=14 and anti‐(OEDOS)_n=7–12 oligomers can act as low‐band‐gap polymers. Therefore they can absorb more sunlight based on maximum wavelength (higher than 620 nm). Furthermore, a red shift in the simulated absorption spectra of (OS)_n and (OEDOS)_n donors is observed. It is found that (OS)_n=14,15 with syn configuration of the extended oligomers is the most suitable donor for the design of high‐performance organic solar cells possessing a narrow electronic band gap, high exciton lifetime and broad and intense absorption spectra that cover the solar spectrum leading to complete light‐harvesting efficiency.     

Two-dimensional model of elastically coupled molecular motors

A flashing ratchet model of a two-headed molecular motor in a two-dimensional potential is proposed to simulate the hand-over-hand motion of kinesins.Extensive Langevin simulations of the model are performed.We discuss the dependences of motion and efficiency on the model parameters,including the external force and the temperature.A good qualitative agreement with the expected behavior is observed.