TADF激基复合物主体材料提升溶液法制备蓝色荧光有机发光二极管的效率

为了提升溶液法制备的蓝色荧光有机发光二极管(OLEDs)的效率,采用了基于热激活延迟发光(TADF)的激基复合物作为主体材料。TADF激基复合物主体可以利用反向系间窜跃上转换形成单线态激子并将能量传递到客体,从而可以同时利用发光层中的三线态激子和单线态激子,以提升蓝色荧光器件的效率。选择蓝色荧光材料1-4-Di-[4-(N,N-diphenyl)amino]styryl-benzene(DSA-ph)作为客体发光材料,4,4′,4″-T-ris(carbazol-9-yl)triphenylamine(TCTA)掺杂1,3,5-Tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)(TPBi)作为热激活延迟荧光激基复合物主体,通过溶液法制备了蓝色荧光OLEDs。通过测试TCTA,TPBi以及TCTA掺杂TPBi的光致发光光谱发现,与TCTA和TPBi相比,TCTA掺杂TPBi的光致发光谱(PL)发生了明显的红移(峰值波长变为437 nm),而且光谱变宽,证明了TCTA∶TPBi激基复合物的形成。通过对于DSA-ph掺杂激基复合物主体的薄膜与DSA-ph掺杂poly(methyl methacrylate)(PMMA)的薄膜进行PL测试发现,两者发光峰相同,都是来自DSA-ph的发光,说明激基复合物主体将能量传递到了DSA-ph;DSA-ph的吸收光谱与激基复合物主体的PL光谱存在很大重叠,说明激基复合物主体与DSA-ph的能量传递非常有效;通过对激基复合物主体掺杂不同浓度客体的薄膜进行瞬态PL衰减测试发现,与纯DSA-ph的寿命相比,DSA-ph掺杂激基复合物主体之后其寿命会延长,纯DSA-ph的寿命只有1.19 ns,DSA-ph掺杂激基复合物主体的荧光衰减曲线与激基复合物主体的荧光衰减曲线相似,这进一步证明了激基复合物主体将能量传递到了DSA-ph。研究了主体引入以及DSA-ph掺杂浓度对器件性能的影响。对于器件的亮度、电流密度、电压、电流效率、电致发光光谱等参数进行了测试,与不采用激基复合物主体的器件相比,采用激基复合物主体的器件性能明显改善,在DSA-ph掺杂浓度为10%时,器件亮度从2133.6 cd·m^-2提升到了3597.6 cd·m^-2,器件效率从1.44 cd·A-1提升到了3.15 cd·A-1,发光峰只有来自DSA-ph的发光。采用TADF激基复合物主体的方法有潜力实现溶液法制备的高效蓝色荧光OLEDs。     

小分子掺杂高分子半导体薄膜中异质结结构光谱学特性研究

利用稳态吸收和荧光光谱学、瞬态荧光光谱学(时间相关单光子计数技术)系统研究了EPPTC掺杂的F8BT薄膜异质结结构中激发复合体的形成机理和荧光发射特性,并表征了其特征光谱和荧光发射寿命. 其特征主要体现在显著延长的荧光发射寿命和红移的荧光发射光谱.这对于理解有机半导体材料异质结结构形成的机理和光物理学特性研究提供了多方面的实验依据.同时,由于这两种材料混合后的吸收光谱较宽范围地覆盖了可见光谱区,这样的有机半导体掺杂工艺对于有机光伏器件和太阳能电池器件的应用研究具有重要意义.     

混合发光层有机电致发光器件中的多重成分发射

以等摩尔空穴传输材料TPD和电子传输材料PBD组成结构为ITO/TPD/TPD∶PBD/PBD/Al的混合物发光层有机电致发光(EL)器件,观察到了相对于组成材料的荧光光谱红移的宽发射带。通过比较EL光谱,光致发光光谱及EL光谱分解,表明电致发光中同时包含单体发射、激基复合物和电荷对复合物的发射。激基复合物为TPD的激发态TPD*与PBD的基态相互作用形成TPD*PBD类型的复合物,电荷对复合物是带电荷的空穴传输分子(D+)的空穴和电子传输分子(A-)的电子交叉复合而形成的(D+-A-)*复合物。各激发态在电场作用下呈现不同的形成机理和复合过程,并且单体发射和激发态复合物的比例随电场而变化,导致发射光谱随电场增强而蓝移。该器件的最高亮度和最大外部量子效率分别为240 cd·(cm2)-1和0.49%。有机固态界面激基复合物或电荷对复合物的发射常出现宽的红移发射带,是调节发光颜色的有效手段。     

电子传输层PBD对Alq3：DCJTB电致发光器件的影响

以PBD为电子传输层制作了一组掺杂型有机电致发光器件,并研究了掺杂器件中PBD对器件的光谱、亮度等的影响。发现PBD与NPB和DCJTB分别掺杂的器件的光谱与其它的器件不同,然后运用了载流子的注入、传输及PBD的传输特性等方法对光谱做出了合理的解释,并运用高斯截谱的方法分析了各个发光峰的产生原因。     

Proton N.M.R. of trismethylenemethaneiron tricarbonyl in a nematic liquid crystal

Single crystals of the cycloadduct of 1-(9-anthryl)-3-(1-naphthyl)propane (CANP) have been prepared, enabling a photochemical and photophysical study to be made of the anthracene-naphthalene sandwich pair in this material. The low temperature fluorescence spectrum is broad, exciplex in nature, and has a decay time of about 80 ns. This emission is quenched as the temperature is raised by a process which involves photocyloaddition of the pair. Arrhenius plots give an activation energy of about 600 cm^-1 for the photochemical process. The analogous photophysical properties have also been studied in methylcyclohexane glasses at 77 K and 60 K. Formation of the sandwich pairs at 77 K gives rise to a ‘ partially relaxed ’ pair having some structure in its emission spectrum and a shorter lifetime. Possible reasons for the differences in properties of sandwich pairs in methylcyclohexane glasses and the parent cycloadduct crystals are discussed. Very weak emission from the naphthalene moiety of monomer ANP has been observed at 77 K.     

Laser cooling of a solid by 21K starting from room temperature

A fluorozirconate glass doped with trivalent ytterbium ions has been laser cooled in vacuo from 298 to 277 K by optical pumping of the ions at 1015 nm. The cooling effect arises from anti-Stokes fluorescence of the laser-excited ions and by virtue of the near-unit fluorescence quantum efficiency for Yb(3+) in sufficiently pure solid hosts. The sample temperatures in the experiment are determined by measurement of the Yb(3+) emission spectrum; the value of the observed temperature change from room temperature as a function of pump wavelength is successfully explained in terms of a simple two-level model that includes the effect of optical saturation.     

Enhanced Exciplex Emission of Pyrene Thin Films Doped by Perylene: Structural,Photophysical and Morphological Investigation

The present work reports on the preparation of thin films of pyrene luminophors doped by varying amounts of perylene by spin coating technique. The structural, morphological, and photophysical properties of pyrene thin films have been investigated as a function of perylene contents. X-ray diffraction studies of doped thin films show well-defined peaks, and estimated crystallite size decreases with increasing perylene content, due to the formation of closed packed crystal structure. SEM images of pure pyrene revealed smooth, and compact and separated crystals with amounts of perylene. The result of absorption spectra showed decrease in intensity with perylene content. However, the fluorescence spectra of pyrene containing higher amounts of perylene showed broad and structureless exciplex emission at 510 nm. The emission colour of pyrene luminophors tuned from blue to green by controlling the concentration of perylene. The phenomenon of change in colour was seen due to efficient excitation energy transfer from pyrene to perylene in thin films. It also found that the intensity of exciplex emission increases with increasing concentration of perylene is of high demand in fluorescent lamp as well as green organic light emitting diodes.     

Analysis of the Effects of Protic,Aprotic, and Multi-Component Solvents on the Fluorescence Emission of Naphthalene and its Exciplex with Triethylamine

The emission spectra of naphthalene (NP)–triethylamine (TEA) systems were measured under steady-state illumination conditions in some protic and aprotic solvent-tetrahydrofuran (THF) mixtures. The fluorescence spectrum of the NP–TEA system in THF could be separated into two component bands (band A at 329 nm (fluorescence of NP) and band B at 468 nm (emission from an intermolecular exciplex)). The intensities of bands A and B decreased with increasing solvent polarity. The intensity of band B also decreased owing to the hydrogen-bonding interaction between TEA and protic solvents, but in this case the intensity of band A increased. The decrease in the intensity of band A with increasing solvent polarity is considered to be caused by the enhanced formation of an ion-pair parallel to the formation of an exciplex with increasing solvent polarity. The decrease in the intensity of band B is considered to be caused by the enhanced formation of ion-pair both parallel to and through the formation of the exciplex. The increase in the intensity of band A and the decrease in that of band B upon the addition of protic solvents is caused by the decrease in the concentration of free TEA. Acetonitrile only has a polar effect and trichloroacetic acid only has a hydrogen-bonding (protonation) effect, while alcohols have both the effects.     

Spectroscopic characterization of the fluorobenzene/DEMA tracer system for laser-induced exciplex fluorescence for the quantitative study of evaporating fuel sprays

Quantitative analysis of laser-induced exciplex fluorescence (LIEF) requires knowledge of the spectral characteristics of all the involved substances. The temperature dependence of the ratio of exciplex and monomer in the liquid phase as well as the temperature-dependent fluorescence intensity from monomers in the gas phase must be known when quantifying signals and correcting for cross talk between liquid and vapor phase. In this work we present an extensive characterization of the fluorescence of the fluorobenzene/diethyl-methyl-amine (DEMA)/n-hexane exciplex system. We use a mixture of 2% fluorobenzene, 9% DEMA, and 89% n-hexane, which was tested before for its coevaporative behavior. The temperature dependent fluorescence of the liquid exciplex was studied in a thin layer cell with UV-light (266 nm) excitation. Cross talk of a known combination of bandpass filters was quantified for the relevant temperature range. The temperature dependence of the gas-phase absorption and fluorescence signal (fluorobenzene) was studied in a heated static cell and a heated gas stream in a nitrogen coflow, respectively. These measurements provide the background for the application of LIEF for quantitative analysis of vapor and liquid distributions in fuel sprays.     

Structural effects on intramolecular exciplexes of 1-amino-3-anthryl-(9)-propanes

The photophysical behavior of six 1-(N-aryl-N-alkyl)-amino-3-anthryl-(9)-propanes was studied by steady-state and time-resolved fluorescence measurements in methylcyclohexane/ isopentane (MP). Structurally, these compounds are most suitable for the formation of intramolecular exciples as shown by the high exciplex quantum yields. The rate constants and the activation energies show that the rate of the exciplex formation depends on steric effects of the N-alkyl group and on the donor effect of the N-aryl group. From the rise curves of the exciplex emission it follows that also in nonpolar solvents exciplexes with a conformation deviating from the favored sandwich structure can be formed. The solvent effect on the fluorescence properties was investigated.     

Tb3+掺杂高密度锗酸盐闪烁玻璃的发光性质

采用高温熔融法制备了Tb³⁺掺杂高密度锗酸盐玻璃。分别测试了该玻璃的透过光谱、密度、荧光光谱、荧光寿命及X射线激发发光光谱,揭示了该玻璃的物理化学性质和发光性质。透过光谱表明该玻璃具有良好的可见光透过率。高含量的Lu₂O₃和Gd₂O₃使得玻璃的密度高达6.4 g/cm³。该玻璃在377 nm光和X射线激发下发出强的绿光。544 nm发光的荧光寿命为1.325~1.836 ms。研究结果表明,Tb³⁺掺杂高密度锗酸盐玻璃是一种可用于慢速事件X射线探测器的候选闪烁材料。     

激发单色仪波长校准的标准物质的探索

找到了一种用于荧光光谱仪的激发单色仪波长校准用的标准物质。用光激发氧化钬滤光片标准物质GBW(E)130112时,能发射547.7 nm的荧光谱线。测量547.7 nm荧光的激发谱,发现激发谱峰的波长测量值为333.56, 360.43,418.39 nm,与上述标准物质证明材料所给出的真值333.8, 360.9,418.5 nm吻合得较好,说明用氧化钬滤光片标准物质GBW(E)130112可以用来作为荧光光谱仪的激发单色仪校准用的标准物质。如果选用发光效率高的材料作为稀土离子掺杂的基质和有效地提高样品的纯度、减小交叉弛豫,那么,氧化钬滤光片作为荧光光谱仪的激发谱波长校准用的标准物质的性能还会有大幅度的提高。     

掺钕镉铝硅酸盐玻璃的Judd-Ofelt理论分析与光谱特性

以掺杂光子晶体光纤为介质的光纤激光器一直受到科研工作者的广泛关注,应用于光子晶体光纤纤芯的掺稀土元素玻璃的制备成为研制掺杂光子晶体光纤的关键问题。利用高温熔融工艺制备钕离子掺杂的40SiO_2-14Al_2O_3-(40-x)CdO-2Li2O-2K2O-2Na_2O-xNd_2O_3(x=0.07,0.14,0.21,0.35,0.42,0.56mol)重金属硅酸盐玻璃系统,测试了其吸收光谱和荧光光谱。采用Judd-Ofelt理论,计算了玻璃样品的强度参数Ωt(t=2,4,6)以及钕离子的自发辐射概率、荧光分支比、荧光辐射寿命等参数。利用测得的荧光光谱计算了钕离子能级跃迁4 F3/2→4 I11/2的受激发射截面及荧光有效线宽。结果表明:当掺Nd_2O_3的摩尔分数为0.42时,制备的镉铝重金属硅酸盐玻璃具有较大的受激发射截面和比较宽的荧光有效线宽,且与相关文献中的钕离子掺杂玻璃相比,具有良好的激光性能和增益性能,有望在研制掺杂光子晶体光纤中得到应用。     

KMgF3中Eu2+的f-f跃迁及其影响因素

研究了KMgF3多品粉末中Eu2+的f-f跃迁及温度、浓度和卤离子等对这种跃迁的影响。发现了荧光光谱的某些规律性。提出了掺溴离子的KMgF3:Eu2+用作高压汞灯材料的可能性。     

Laser cooling of a solid by 65K starting from room temperature

In vacuo laser cooling of a solid from 301 to 236 K has been demonstrated. The sample consists of a cladded, multimode optical fiber fabricated from the fluorozirconate glass ZBLANP; the fiber's waveguiding core is doped with 1 wt. % Yb(3+) ions. Cooling of the host glass results from anti-Stokes fluorescence of Yb(3+) following optical pumping in the long-wavelength tail of the ion's absorption spectrum (lambda=1015nm) . Measurement of the time constant for equilibration of the sample temperature is in excellent agreement with an analytic calculation of this quantity.     

A Low-Field Magnetically Affected Reaction Yield (MARY) Spectrometer with Spectral Fluorescence Resolution

A novel spectrometer for low-field studies in magnetically affected reaction yield (MARY) spectroscopy with fluorescence detection is described. The spectrometer is based on a yoke-free magnetic system containing no ferromagnetic elements, uses X-ray or optical excitation, and includes a monochromator to analyze the spectral composition of luminescence. Using the new setup, the effect of transversal residual magnetic field on zero field MARY line is illustrated, formation of exciplexes under X-irradiation in a naphthalene/N,N-dimethylaniline solution in alkane is demonstrated, a magnetic field effect on the emission spectrum is shown in field-cycling mode, and modulated MARY spectra in the exciplex and the intrinsic luminophor bands are compared to show that magnetic field sensitivity here is provided at the stage of the recombining radical ion pair, while exciplex formation only transforms the luminescence properties.     

Fluorescence quenching of phenanthrene and chrysene by potassium iodide in methanol-ethanol solutions

The fluorescence decay functions and the fluorescence quantum yields of phenanthrene-h₁₀, -d₁₀, chrysene-h₁₂ and -d₁₂ in the presence of Kl in methanol-ethanol solutions were measured at 77 K and 293 K. The fluorescence decay functions measured at 77 K were analyzed taking into account the distance dependence of the intersystem crossing and radiative fluorescence rate constants. The kinetic effects and spectral evidence suggest that for the external heavy-atom effect in the system investigated here both the electron transfer processes and the exciplex formation between the aromatic molecule and perturber are important.     

Fluorescence study of inter- and intramolecular interactions in poly(p-N,N-dimenthylaminostyrene-co-9-vinylantracene)

A new exciplex-forming polymer, poly(p-N, N-dimethylaminostyrene-co-9-vinylanthracene) (PDMA-AN, DP ≈ 25) was prepared by copolymerization of p-N, N-dimethylaminostyrene and 9-vinylanthracene. Exciplex formation was observed both in the fluid media and a polymer film. The fluorescence spectrum of PDMA-AN is characterized by the appearance of a high-energy exciplex formed by the neighboring pendant 9-anthryl (AN) and p-N, N-dimethylanilino (DMA) groups, which is shifted by approximately 85 nm to shorter wavelengths in comparison with the emission band of the intermolecular exciplex formed by the monomer model anthracene-p-N, N-dimethylaminotoluene (DMAT). The polymer conformation appropriate for the formation of this state exists prior to the initial excitation and is partially eclipsed. The effects of concentration and polarity of the solvent on the flourescence emission are discussed. A red shift of the maximum wavelength of the flourescence band as a function of concentration was found in a nonpolar solvent (toluene). However, in a relatively polar solvent (1,2-dichloroethane), a shoulder peak at a longer wavelength gains in intensity with increasing concentration. These phenomena are attributed to the increase of the contribution of the normal intermolecular exciplex state in which the interacting AN-DMA groups achieve an eclipsed and sandwiched conformation.     

用光线量子论研究掺铒磷酸盐玻璃微球发光的形貌共振

介绍微腔研究理论的发展和微球腔中的光线量子论。测试了488nm激光激发下掺铒磷酸盐玻璃微球的1533nm荧光光谱，分析其谱线中的形貌共振现象及形成机制，并将掺铒磷酸盐玻璃微球的荧光光谱和掺铒磷酸盐体玻璃的荧光光谱进行比较。从实验中得到了掺铒磷酸盐玻璃微球产生的单模振荡幅度。