Ir（PPY）3对Rubrene荧光材料的敏化性研究

最近几年,磷光器件是有机电致发光研究领域和产业化的一大热点。在实验中作者发现PVK∶PBD∶Rubrene共掺体系的发光中存在较强的PVK发光,能量传递不充分。由于一些具有重金属离子的有机物,存在强的自旋-轨道耦合作用,引入到共掺体系可以充分利用单线态和三线态的发光,从而获得高于一般有机材料器件所达到的内量子效率。为获得单色性较好的Rubrene发光,作者将磷光敏化剂Ir(ppy)3引入到PVK∶PBD∶Rubrene共掺溶液中,得到了纯正Rubrene发光,Forester能量传递也更加充分。当进一步提高Rubrene掺杂浓度以后,单色性Rubrene发光更加明显,并讨论了Ir(ppy)3所起的作用和器件的发光机理。磷光材料与有机小分子材料共掺的方法,可以有效提高器件的发光亮度及效率。     

塑料闪烁体基质到溶质的能量传递

本文研究了以聚苯乙烯为基质,添加具有不同光谱荧光性质溶质的二元塑料闪烁体的发光.测量了闪烁体的激发光谱,荧光光谱,γ射线,X射线和紫外线激发的相对发光强度及其与溶质浓度的关系,测量了聚苯乙烯吸收波长和溶质吸收波长激发下的发光衰减及其与溶质浓度的关系.讨论了基质到溶质的能量传递机制.     

PEG400对Eu(BA)3/SiO2发光性能的影响

稀土有机配合物进行无机化能提高热稳定性,但无机化基质对稀土有机配合物的荧光性影响较大,采用PEG3400对复合体进行改性,有利于改善荧光性.文章采用溶胶-凝胶法合成Eu(BA)3/SiO2和Eu(BA)3/PEG400-SiO2复合发光材料.研究了PEG400掺入量对SiO2中Eu(BA)3发光性能的影响,PEG400作为路易斯硬酸和稀土离子配体增强了Eu(BA)3的发光性能.用红外光谱说明PEG400的掺人有利于减少发光材料中的结晶水和羟基数目.通过原子力显微镜分析了PEG400的掺入量对SiO2基质结构的影响.     

染料掺杂的红色有机薄膜电致发光器件

近年来 ,有机发光二极管 (OL EDs)得到了广泛深入的研究[1～ 3] 。研究工作主要集中在探索新的有机荧光材料、载流子注入和输运材料 ,以及器件的新结构 ,力求得到发光效率高和稳定性好的各种不同颜色的发光。从目前的研究来看 ,尽管蓝色和绿色发光材料的效率已经足够高到实用 ,但红色发光材料仍然存在问题 ,对红色发光进行研究是非常必要的。有两条实现红色发光的途径 :掺杂能发红光的染料和用稀土离子配合物作基质或激活剂。利用能量传递的原理 ,在有机基质材料中掺杂荧光染料是获得高效、长寿命和所希望发光颜色的一种有效而简单的方法…     

固体中过渡金属离子占位、价态及光谱性质的第一性原理研究EI北大核心CSCD

过渡金属(TM)激活离子由于在近红外发光、红外激光、荧光转化的白光LED、荧光温度计、余辉发光等方面的优异性能和应用潜力而被广泛研究。TM离子在固体中可占据八配位、六配位、四配位等多种配位格位,可呈现多种价态且光跃迁性质强烈依赖于晶体环境,因此TM离子在固体中的发光中心确定、发光机理理解和性能预测存在困难。本文通过第一性原理计算探索固体中TM离子的热力学和光跃迁性质。内容包括:通过对各种化学氛围下形成能的计算结果,分析基质的本征缺陷以及TM离子占位、价态、分布和浓度;理解不同晶体环境中TM离子的各激发态和能级结构;构建位形坐标图分析激发、弛豫、发射及猝灭过程;提出通过合成氛围、共存条件和离子共掺等方式调控或优化TM离子的占位、价态和光跃迁的方案。本文以若干具有代表性的体系为依托,展示了如何运用第一性原理计算手段进行掺TM离子固体发光材料的研究。具体所涉及的代表体系和研究内容为:Ti:Al_(2)O_(3)激光晶体中红外残余吸收机理及其减弱或尽可能消除的方法,典型尖晶石和石榴石基质中Mn^(2+)、Mn^(3+)、Mn^(4+)的占位和激发、弛豫、发射等光跃迁性质,固溶氧化物基质中铬离子的占位、价态及相应的光跃迁性质等,表明第一性原理计算可用于发光材料的机理研究、理性设计和优化。     

二维纳米材料及其衍生物在激光防护领域中的应用

为了实现同步防护脉冲激光和连续波或准连续波激光的攻击,人们在过去几十年间已经投入了大量的人力和物力来研发高性能光限幅材料.石墨烯、过渡金属硫化物、黑磷等二维纳米材料拥有许多优异独特的性质,激发了全世界的广泛研究兴趣.本文简要回顾了基于石墨烯、黑磷、过渡金属硫化物和钙钛矿等最具代表性的二维材料及其有机/高分子衍生物在激光防护领域中的研究进展、存在的亟待解决的关键科学问题和未来的发展趋势.为了充分利用这些二维纳米材料的优点,人们可以使用功能小分子或聚合物与它们进行共混掺杂,制备复杂的多相材料体系,也可以将可溶性的有机/高分子共价功能化的二维纳米材料掺杂于高分子基质中形成主客体复合材料,这些制备方法有助于促进或提高整个体系的光限幅能力.总而言之,一个优化的复杂的多组份纳米材料体系能极大地增强光限幅器件的性能和适应性.此外,开展二维纳米材料和它们的衍生物在不同固体基质中展现出来的光物理和光子性质研究,将有助于在分子水平上实现对这些纳米材料的改性.     

聚变反应历程测量系统研制及应用

为了测量惯性约束聚变实验中的聚变反应时间过程,研制了一套时间分辨优于40 ps的聚变反应历程测量系统.该系统由闪烁体及鼻锥部分、光学系统和条纹相机系统三部分组成.其中闪烁体将中子信号转换为可见光信号,光学系统则将闪烁体的发光信号成像在条纹相机上进行记录.为得到信号与入射激光的时间关系,还将时标引入了条纹相机进行记录.在...     

共掺氧化镱对掺铋硅酸盐玻璃的发光性能调控

掺铋玻璃及其光纤材料在近红外（中心波长1300nm）具有200-400nm的超宽带发光特性，是用作超宽带光纤放大、可调谐激光以及飞秒激光的理想基质材料。武汉光电国家实验室李进延教授带领的新型光纤材料与器件团队从事新型光纤材料与器件的前沿研究。     

固态高分子体系多尺度分子运动的核磁共振研究

固体核磁共振技术是研究固态高分子材料中结构和分子动力学的一种非常重要和有效的手段. 该技术的一个重要特点是可以通过合理的实验方法,实现对研究体系中从低频(Hz)到中频(kHz)乃至高频(MHz)范围内分子运动的观测. 因此,固体核磁共振技术非常适合研究高分子体系中各类不同尺度分子运动. 该文首先简要介绍核磁共振研究分子运动的基本原理和方法,以及固态高分子体系的结构和分子动力学特点,然后结合固态高分子体系中的一些例子对核磁共振在固态高分子多尺度分子运动方面的一些研究成果展开讨论.     

稀土配合物与PVK共混体系发光特性及载流子复合区域转移的研究

合成了一种新型的铽钆共掺稀土配合物TbGd(BA)6(bipy)2,把它作为发光材料应用于有机电致发光中。文中摸索了器件优化条件,并讨论了TbGd(BA)6(bipy)2与PVK共混体系的发光机理和载流子复合区域的转移。稀土配合物的光致发光是由于外部直接激发及PVK到稀土配合物的能量传递。电致发光有两个途径,PVK到稀土配合物的能量传递及载流子的直接俘获。在双层器件中,发光区域随Alq3厚度变化,尤其是在高电压下,载流子复合区域移向Alq3一侧,而在增加BCP作为空穴阻挡层的多层器件中,载流子限制在发光层和空穴阻挡层的界面处复合,随着电场的增强,铽发光趋于饱和,而出现了高分子基质的发光。优化后,得到213 cd·m-2明亮的铽的绿色发光。     

Energy-resolved analysis of ferroelectric electron emission from TGS using emission electron microscopy

Ferroelectric electron emission arises when the spontaneous polarization of a ferroelectric is switched due to the application of an electric field. In order to study the origin of emission and the related emission mechanism, space-resolved emission electron microscopy has been employed. The integral energy distribution of the emitted electrons from triglycine-sulfate surfaces has been investigated using a cylindrical sector analyzer and an imaging retarding field analyzer. Space-resolved emission photography and energy distribution measurements were obtained, revealing the effect of ferroelectric switching on the electric field distribution and hence on the emission process. Evidence of secondary electron emission from the metal electrodes has been found.     

Pre-equilibrium emission effect in (n,p) reaction cross-sections at 14.8 MeV

The influence of pre-equilibrium emission on (n, p) reaction cross-sections at 14.8 MeV has been studied. Cross-sections for (n, p) reactions have been measured by the activation technique at 14.8 .1; 0.5 MeV neutron energy. The experimental cross-section values have been compared with the calculated values at 14.8 MeV with and without considering the pre-equilibrium emission. Equilibrium calculations have been performed according to the statistical model of Hauser and Feshbach while the hybrid model has been used to include the pre-equilibrium contribution. Pre-equilibrium emission has been considered only in the first emission step. The comparison of experimental and calculated values clearly indicates the presence of pre-equilibrium emission.     

气相外延ZnSe单晶膜室温蓝色发射的复合过程

随着激发密度的增加,ZnSe外延单晶膜的室温蓝带Es′(～4650Å)表现出红移和展宽,其行为与77K时得到的相一致。在200-300K温度范围内,测得Es′谱带的热激活能为19meV,它与ZnSe晶体自由激子的束缚能20meV十分接近。上述结果从实验上进一步证明了ZnSe外延单晶膜室温蓝带Es′起源于受导带中自由电子散射的自由激子的衰减。     

Blue Cooperative Luminescence In Yb3+-Doped Barium Gallogermanate Glass Excited At 976 nm

The Yb³⁺-doped barium gallogermanate glass has been prepared via the conventional melt method. The absorption spectra, the near infrared emission spectra, the upconversion emission spectra and the differential scanning calorimetry have been measured. Bright blue upconversion emission centered at 476 nm has been observed under the 976 nm laser diode excitation at room temperature. The blue upconversion emission mechanism has been discussed on the blue emission intensity and the measured lifetime. The slope of the log-log plot of the blue emission intensity versus the pump power is equal to 1.98, and the blue luminescence decay time is half of the near infrared fluorescence decay time, confirming that the blue emission comes from Yb³⁺-Yb³⁺ pairs cooperative upconversion mechanism. The result of differential scanning calorimetry suggests that this type of glass is suitable as a potential candidate for fiber drawing.     

The luminescence of self-activated and copper-doped zinc selenide

The photoluminescence excitation and emission spectra of crystals of zinc selenide doped with copper or chlorine have been measured. The luminescence studies show that crystals doped with chlorine contain a slight trace of copper contaminant. Since the self-activated emission associated with chlorine and the low-energy copper emission overlap in the red region of the spectrum, it is necessary to remove all traces of copper from a crystal to isolate the self-activated emission. This has been done by heating crystals in molten zinc. In this way it has been possible to show that at 85 °K the self-activated emission band lies at 6150 Å, whereas the copper-red emission occurs at 6400 . The self-activated emission is excited strongly in a band centred at 4850 Å, while the copper-red emission is excited in a band centred at 5100 Å. The various transitions Å involved are discussed.     

Photofield emission from SiGe nanoislands under green light illumination

Photofield emission from SiGe nanoislands formed by molecular beam epitaxy (MBE) have been investigated. Two types of nanoislands, namely the domes and pyramids with different heights, have been addressed. It was found that the arrays of SiGe nanoislands exhibited a low onset voltage for field emission. The increase of emission current and the decrease of the curve slope in Fowler-Nordheim coordinates under green light illumination have been revealed. Electron field emission and photoemission from SiGe nanoislands have been explained based on the energy band diagram of Si-Ge heterostructure and some energy barriers have been determined.     

Spontaneous emission of positronium negative ions from polycrystalline tungsten surfaces

Recently, the spontaneous emission of positronium negative ions from polycrystalline tungsten surfaces was observed. In the present work, the emission of these ions in ultra-high vacuum has been studied and the long-term stability of the emission efficiency has been investigated.     

Visualization of field induced ferroelectric electron emission from TGS using emission electron microscopy

Field induced electron emission from triglycinesulfate (TGS) has been investigated using parallel imaging electron emission microscopy (EEM). The emission phenomenon has been induced by applying an ac electrical field up to 2 kV/mm to a single crystal of approximately 0.1 mm thickness. Emission patterns have been observed as a function of the applied field amplitude and of the crystal temperature. At voltages below the coercive field, no emission is visible. When approaching the Curie temperature, emission gradually disappears. This indicates an electron emission mechanism relying on the existence of a switchable ferroelectric phase. The information content of the images is discussed, an interpretation is given on the basis of existing theories. PACS 68.37.-d; 77; 77.80.Fm; 77.80.-e     

On the influence of the Reynolds number on the intensity of vortex sound flowing around a cylindrical profile

Regularities of the emission of vortex sound (eolian tone) during air flow around stationary and rotating cylindrical profiles have been investigated. The influence of the flow Reynolds number on the intensity of vortex sound emission has been estimated from results of measuring the pressure fluctuation distribution on the surface of stationary cylindrical rods flowed around by air, as well as in the wake behind them. It is shown that the emission intensity depends on the location of the point of flow detachment from the profile surface and the track width near the profile. The ranges of the flow Reynolds numbers where the emission intensity increases with different flow velocities have been determined by analyzing the dependence of the profile lift coefficient on the Reynolds number. An independent way of determining the profile lift coefficient by measuring the vortex sound intensity is proposed. The results explain contradictions between the results of some authors, who experimentally observed different dependences of emission intensity on the flow velocity. The influence of the profile diameter on the vortex sound emission intensity has been investigated. The boundary Reynolds number above which the profile diameter does not affect emission has been established for stationary and rotating cylindrical profiles. It is shown that deposition of rough coatings on the rod surface may reduce the vortex sound emission intensity by affecting the point of flow detachment from the surface.     

太赫兹源场致发射电子源

通过粒子模拟(PIC)软件模拟计算了在ps级别下二极与三极结构碳纳米管场致发射的电流密度与电子注聚焦性能。阳极电压在2 kV时,二极结构下电流密度达到1.85 A/cm2;三极结构下,栅压700 V时发射电流密度达到2.3 A/cm2,且在一定的三极结构参数与电极电压下,可以获得较好的电子注聚束效果。通过碳纳米管二极管发射实验,获得了6.6 A/cm2的发射电流密度,总发射电流达到52.1 mA,可以为太赫兹器件提供连续发射的电子注。