DCM掺杂PVK体系的超快光谱

利用稳态荧光光谱和时间分辨超快光谱研究了DCM掺杂PVK(聚乙烯咔唑)体系的发光特性和能量转移。根据DCM的吸收光谱与PVK的荧光光谱,用Frster理论估算出DCM:PVK掺杂体系能量转移的临界半径及其效率。在DCM:PVK掺杂薄膜中,随着掺杂浓度的升高,DCM的发射强度增强,PVK的发射强度减弱,两者相对强度之比与估算结果一致。还利用时间分辨超快光谱研究了DCM:PVK掺杂薄膜体系的能量转移动力学过程,观察到DCM:PVK掺杂薄膜的荧光寿命随着掺杂浓度的升高逐渐变短。结果表明,在DCM:PVK掺杂薄膜中,存在从PVK到DCM较为有效的Frster能量转移。     

一种多层白色磷光有机电致发光器件的制备及性能研究

制备了一种结构为ITO/NPB/NPB:Ir(piq)₂(acac)/CBP:TBPe/BAlq:rubrene/BAlq/Alq₃/Mg:Ag的白色磷光有机电致发光器件.其中空穴传输型主体NPB掺杂磷光染料Ir(piq)₂(acac)作为红色发光层,双载流子传输型主体4,4′-N,N′-dicarbazole-biphenyl (CBP)掺杂TBPe作为蓝色发光层,电子传输型主体材料BAlq掺杂rubrene作为绿色发光层.以上发光层夹于 关键词： 电致发光 磷光染料 异质结 白光     

不同掺杂顺序的磷光OLED器件发光性能的研究

绿色GIr1和红色R-4B磷光染料,采用红绿红、绿红、红绿、绿红绿等顺序,与主体材料CBP共蒸,制备了四种红绿磷光器件,并结合TCTA和BCP对载流子和激子的阻挡作用,研究了发光层掺杂顺序对器件性能的影响。结果表明,四种器件光谱、光效、亮度和发光颜色均有较大差异,且BCP和CBP界面附近是主要的激子复合区。在电压为5v,红绿红掺杂型器件,亮度、电流效率和色坐标分别为40.12 cd·m-2,7.68 cd·A-1 和(0.630 1,0.365 4);而绿红绿掺杂型器件为104 cd·m-2,19.75cd·A-1和(0.371 7,0.576 8)。分析认为：CBP与GIr1,R-4B,BCP,TCTA有较大的LUMO能级差异,发光层中电子的主要传输方式为掺杂分子上的俘获和分子间跳跃,不同掺杂顺序会形成不同能级势垒分布,发光层内电荷累积形成的空间电场分布不同。     

Effect of electric field, temperature, and defect formation on processes of nonequilibrium carrier emission from InAs/GaAs quantum dots

The effect of electric field, temperature, and defect formation on the processes of nonequilibrium charge-carrier emission from InAs/GaAs quantum dots grown by vapor phase epitaxy is studied by photo-electric spectroscopy. It is shown that, under a relatively low electric field strength, the main mechanism for carrier emission is thermally activated emission; in strong fields, it is tunnel emission. Formation of defects under anodic oxidation of the surface leads to suppression of charge carrier emission from quantum dots due to the appearance of an effective recombination channel.     

Phosphorescence emission from BAlq by forced intersystem crossing in a colloidal photonic crystal

Bis(2-methyl-8-quinolinato)-4-phenylphenolate aluminium (BAlq) does not show phosphorescence. Only in the presence of an emitting sensitiser and at low temperature, phosphorescent emission has been reported from this molecule. We report for the first time, up to our knowledge, phosphorescent emission from BAlq at room temperature in the absence of sensitisers by trapping the molecule in a photonic crystal (PhC). BAlq has been embedded first in a polymer matrix and subsequently inserted within a colloidal PhC in order to create the optical confinement that suppresses the available energy modes for fluorescence and favours intersystem crossing, giving rise to the unusual triplet emission.     

基于PVK的高色纯度高稳定性有机电致红光器件

利用旋涂法和真空蒸镀法相结合的方法,根据能量空间传递的原理制备了PVK ∶ Ir(piq)₂(acac)体系的红色有机电致发光显示器件。器件的结构为ITO/CuPc/PVK ∶ Ir(piq)₂(acac)/BCP/Alq₃/LiF/Al。研究了不同主客体掺杂比对器件发光性能的影响,得到了高色纯度、单色性较好的红光器件。当Ir(piq)₂(acac)掺杂的质量比为1 ∶ 0.08时,器件的综合性能达到最佳,发光峰位于625 nm,CIE坐标为(x=0.66,y=0.33)。通过对各层厚度的合理选择,形成相对优化的微腔结构,充分利用其对光谱的窄化效应,使得器件的EL光谱的发射半峰全宽仅为55 nm,提高了器件的发光性能。器件光谱具有很好的单色性,色纯度达到98.2%。     

磷光材料fac-tris(2-phenylpyridinato-N，C2′)iridium(Ⅲ)对不同荧光材料的敏化作用及发光机制分析

在荧光材料中掺杂合适的磷光敏化剂,可以大大提高荧光有机电致发光器件(OLED)的效率。选择磷光材料知fac-tris(2-phenylpyridinato-N,C^2′)iridium(Ⅲ)(Ir(ppy)3)分别与荧光材料4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl(DCJTB)、5,6,11,12,-tetraphenylnaphthacene(Rubrene)掺杂作为发光层,当掺杂质量比合适时,磷光材料的发光消失,得到了纯正的荧光材料的发光。同时,对磷光材料的敏化作用及发光机制进行了分析,比较了Ir(ppy)3对两种不同荧光材料的敏化作用强弱,发现Ir(ppy)3对荧光材料Rubrene的敏化作用更强。对影响敏化作用的因素进行了分析,推测其原因与磷光材料和荧光材料的相容性质有关。     

Ir(PPY)3掺杂PVK的电致发光机理

近几年来发展起来的电致磷光(electrophosphorescence)是有机发光二极管(OLED)研究的新生长点。对电致磷光发光机理的研究随即得到了人们普遍的关注。比较了不同正向偏压条件下Ir(PPY)₃掺杂聚乙烯基咔唑(PVK)的光致发光(PL)和电致发光(EL)光谱。研究结果显示在电场和注入电流的共同作用下,PL光谱中基质PVK发光的相对强度并没有发生显著的变化。电场或注入载流子不会影响PVK向Ir(PPY)₃的能量传递。磷光掺杂聚合物EL主要是由于载流子在掺杂磷光分子上的直接复合,而不是由基质向磷光掺杂分子的能量传递。     

磷光染料掺杂有机分子发光的能量转移研究

用稳态光谱和时间分辨的超快光谱研究了不同浓度磷光染料PtOEP掺杂有机小分子Alq薄膜的发光特性和能量转移.据PtOEP的吸收光谱与Alq的荧光光谱,用Frster理论估算出Alq:PtOEP掺杂体系的能量转移临界半径及其转移效率.稳态荧光光谱显示,在Alq:PtOEP掺杂薄膜中,随着掺杂浓度的升高,PtOEP的发光强度增强,Alq的发光强度逐渐减弱,两者间的能量转移效率与理论计算结果一致.利用时间分辨光谱研究了Alq:PtOEP掺杂薄膜体系的能量转移动力学过程,观察到Alq:PtOEP掺杂薄膜的荧光寿 关键词： 有机掺杂薄膜 稳态光谱 时间分辨光谱 能量转移     

电场变化对有机磷光器件中激子形成影响的研究

激子形成区域随电场变化的移动会使得有机电致发光器件(OLEDs)的效率和色度发生改变,从而影响器件的性能。文章首先制备了两种OLED器件,器件1为ITO/PEDOT∶PSS/PVK∶Ir(ppy)₃∶DCJTB (100∶2∶1 wt)/BCP(10 nm)/Alq₃(15 nm)/Al,器件2为ITO/PEDOT∶PSS/PVK∶Ir(ppy)₃(100∶2 wt)/BCP(10 nm)/Alq₃(15 nm)/Al,研究了电场强度对单层多掺杂结构器件激子形成的影响。实验发现在多掺杂发光层中,随着电压的增加,Ir(ppy)₃,PVK和DCJTB的发光均增强,PVK和DCJTB发光增强更快。对其发光机制进行分析,认为较高电场下,载流子获得较高能量,更容易形成高能量激子,产生宽禁带材料PVK的发光;另一方面,从能级结构分析DCJTB的带隙较窄, 俘获更多的载流子发光更强。同时,在器件的电致发光(EL)光谱发现在460 nm处一新的发射峰, 发光随着电压的增大相对减弱。为了研究460 nm发光的来源,制备了器件：ITO/PEDOT∶PSS/PVK∶BCP∶Ir(ppy)₃(x∶y∶2 wt)/Alq₃(15 nm)/Al, 改变x, y的比值研究发现,460 nm处的发光依然存在,推测此发光峰应与PVK及BCP之间有关。     

Thermoluminescence of the blue light-emitting system based on poly(9-vinylcarbazole) doped with a pyrazoloquinoline dye

We have investigated the charge carrier trapping and recombination mechanisms in electroluminescent systems based on poly(9-vinylcarbazole)/2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole blend, used as the matrix, and the deep blue light-emitting pyrazoloquinoline dye-1-H-pyrazolo[3,4-b]quinoline (PAQ8) dopant. The thermoluminescence studies have shown that the charge carrier trapping occurs on the dye molecules as well as on the matrix components. The traps localized on the PAQ8 molecules compete with the others available in the system, however at higher concentrations of the dye a role of these traps increases. Spectral analyses of the thermoluminescence have indicated that even at low concentration of PAQ8, the dye molecules constitute the dominating recombination centres in the system.     

低效率滚降、发光颜色稳定的磷光白色有机电致发光器件

本文采用多发光层结构,制备了高亮度下具有高发光效率,同时在较宽亮度范围内发光颜色稳定的白色磷光有机电致发光器件(WOLED).在对双发光层结构磷光OLEDs的发光机制和载流子传输过程进行系统研究的基础上,将两种磷光OLEDs的发光层结构相结合,获得的多发光层结构磷光WOLED最大电流效率和外量子效率分别为34.6 cd/A和13.5%;当亮度为1000 cd/m^2时,其电流效率和外量子效率分别为33.9 cd/A和13.3%,外量子效率滚降仅为1.5%;亮度从1000 cd/m^2增至10000 cd/m^2的过程中,其CIE色度坐标从(0.342,0.403)变化至(0.326,0.392),变化量ΔCIE为(0.016,0.011).     

水溶性苝系衍生物荧光探针识别金属离子的光物理机制计算研究

随着人们对荧光化合物电子光谱和光物理行为的深入研究,在利用荧光分子作为探针,检测各种不同体系的状态及其变化等方面都有了巨大的进展。其中,N,N′-二天冬氨酸铵盐-3,4,9,10-四羧酸二酰亚胺(PTCDA)是一种水体环境中选择性好灵敏度高的典型荧光分子探针。本文用密度泛函理论对PTCDA的光物理机制进行研究。计算了PTCDA分子在理想状态下的最优构型,电荷布居和激发光谱。根据计算结果,拟合此苝系衍生物激发态与Cu2+结合前后的吸收光谱,与Cu2+结合前后,吸收光谱峰形相似,加铜后整体吸收峰位发生了红移,有猝灭变色现象。通过与实验值的对比,计算所得分子构型合理有效,激发光谱谱峰位置切合实际。分析得出：PTCDA分子对二价铜离子有较好荧光探测活性,其光信号响应机制属于分子内电荷转移(ICT)机制。当分子接收二价铜离子时,吸收光谱谱峰位置红移,分子内电荷转移方向和强度均发生变化,既有猝灭信号,也有光的颜色变化信号,是一种具有猝灭与变色双信号的荧光探针材料,具有很大的开发潜力。所做工作只是用量子化学计算方法在分子荧光探针领域进行光物理响应机制分析的初步探索,可以为该领域提供系统而有价值的理论参考。     

Emission tuning study of RGB blends. Interaction of two EL polymers and a red dye

A study of light emission in photo- and electroluminescence in blends composed of a blue and a green emitting polymers with a red dye was performed. To gain information about the tunability of the RGB mixture, the blends varied in composition. The polymers were poly(2,7-9,9′-dihexylfluorenediyl) (blue), poly(9,9-di-hexylfluorenediyl divinylene-alt-1,4-phenylenevinylene) (green) and the dye was 4-(dicyanomethylene)-2-methyl-6-(dimethylaminostyryl)-4H-pyrane (red).It was verified that in photoluminescence Forster type energy transfer plays the main role in the emission. In solution a large concentration of the acceptors is needed to attain the transfer radii, whereas in the solid state, the transfer is very sensitive to small variations in the acceptor content, with large changes in emission spectra. The band gaps of the components allowed a cascade energy transfer mechanism. In electroluminescence, apart from the energy transfer mechanism, an important role is played by the trapping of charge carriers, resulting in significant differences between the PL and EL spectra.     

Experiment and simulation of space charge suppression in LDPE/MgO nanocomposite under external DC electric field

In this paper, space charge dynamics under DC electric field of −100 kV/mm in low-density polyethylene (LDPE) and its nanocomposite containing a small amount of MgO nanoparticles were measured using an improved pulsed electro-acoustic (PEA) system. Unlike negative packet-like space charge accumulating in LDPE films, no remarkable space charge was observed in LDPE/MgO nanocomposite films, which indicated that the introduction of MgO nanoparticles played a key role on the space charge suppression. Different with current qualitative models, this paper describes space charge suppression on the basis of simulation using the bipolar charge transport model, which featured bipolar charges injection, transport, trapping, recombination, and extraction process. It was shown from the simulation that trap depth, trap concentration, local electric field and charge injection barrier height were all significant factors on the space charge suppression process. A deeper trap depth in LDPE/MgO nanocomposites made it easier for traps to capture mobile carriers. And a larger trap concentration effectively slowed down the whole carrier movement although there seemed a trap concentration threshold less than 30 Cm⁻³, above which this effect became slight. In addition, both the high permittivity of LDPE/MgO nanocomposites and low local electric field in the vicinity of cathode led to a larger injection barrier height based on the Schottky injection law, which would tremendously block the charge injection. At last, the suppression mechanism of space charge formation in the LDPE/MgO nanocomposites is presented.     

采用瞬态电致发光研究磷光掺杂体系发光瞬时过冲的发射机理

掺杂型有机电致发光器件中载流子累积、载流子复合等物理过程的深入了解对提高器件效率和稳定性有重要作用。通过瞬态电致发光测量可以研究掺杂型有机电致发光器件内部载流子累积。对结构为: ITO/NPB(30 nm)/host: Ir(ppy)₃/BCP(10 nm)/Alq₃(20 nm)/LiF(0.7 nm)/Al(100 nm)的器件分别研究主体材料以及客体掺杂浓度变化对有机掺杂型器件瞬态发光行为的影响。实验发现,当单脉冲驱动电压关闭后,只有TAZ: Ir(ppy)₃掺杂器件出现发光瞬时过冲现象,即发光强度衰减到一定时间时突然增强;且随着客体掺杂浓度的增加,瞬时过冲强度逐渐增强。通过分析TAZ: Ir(ppy)₃掺杂器件的瞬时过冲强度对主体材料与掺杂浓度的依赖关系,进一步发现,瞬时过冲效应强度主要受限于发光层内部积累的电子载流子;TAZ: Ir(ppy)₃发光层内电子容易被客体材料分子俘获并积累,电场突变时陷阱电子容易跳跃到主体材料上并与主体材料上积累的空穴形成激子,激子能量传递到客体材料上并复合发光继而出现发光强度的瞬时过冲现象。研究发光瞬时过冲行为可探究器件发光层内的载流子和激子的动态行为,有利于指导器件的设计,从而减少积累电荷的影响,提高器件的性能。     

Highly Efficient and Stable Hybrid White Organic Light Emitting Diodes with Controllable Exciton Behavior by a Mixed Bipolar Interlayer

Highly efficient and stable hybrid white organic light-emitting diodes(HWOLEDs) with a mixed bipolar interlayer between fluorescent blue and phosphorescent yellow emitting layers are demonstrated.The bipolar interlayer is a mixture of p-type diphenyl(10-phenyl-10H-spiro[acridine-9,9'-fluoren]-3'-yl) phosphine oxide and n-type 2',2"-(1,3,5-benzinetriyl)-tris(l-phenyl-l-H-benzimidazole).The electroluminance and Commission Internationale de l'Eclairage(CIE1931) coordinates' characteristics can be modulated easily by adjusting the ratio of the holepredominated material to the electron-predominated material in the interlayer.The hybrid WOLED with a p-type:n-type ratio of 1:3 shows a maximum current efficiency and power efficiency of 61.1 cd/A and 55.8hn/W,respectively,with warm white CIE coordinates of(0.34,0.43).The excellent efficiency and adaptive CLE coordinates are attributed to the mixed interlayer with improved charge carrier balance,optimized exciton distribution,and enhanced harvesting of singlet and triplet excitons.     

聚合物材料空间电荷陷阱模型及参数

采用电声脉冲测量技术研究了直流电场下低密度聚乙烯材料的电荷入陷和脱陷特征. 发现在不同电场周期下样品的电荷衰减呈现不同的特征, 为此提出了一个简单的基于两陷阱水平的入陷和脱陷模型, 并计算了相应的参数, 如陷阱能级和密度. 确定了不含任何添加剂的低密度聚乙烯样品中存在的两种水平的陷阱能级分别为: 较浅陷阱能级0.77–0.81 eV 对应的浅陷阱电荷密度为(1.168–1.553)× 10¹⁹ m^-3; 较深陷阱能级0.96–1.01 eV 对应的深陷阱电荷密度为(1.194–4.615)× 10¹⁸ m^-3. 最后初步验证了材料的深陷阱能级和对应的深陷阱电荷密度随老化而增加, 可考虑将模型中的两能级陷阱参数作为老化诊断特征参量. 关键词： 聚合物 空间电荷 陷阱 老化     

Recombination zone shift in phosphorescent white organic light-emitting devices with single host structure of multi-emission layers

We have investigated the recombination zone in the phosphorescent white organic light-emitting devices with single host structure of multi-emission layers. Blue, green, and orange-red phosphorescent emitters were doped into the separate layers of single host material for fabricating the white devices with multi-emission layers. The electroluminescence spectrum was substantially modified by the shift of the recombination zone that was dependent upon the thickness of the electron transport layer. We investigated the recombination zone shift in terms of electric field distribution and carrier injection. A maximum external quantum efficiency of 15.9% and a maximum power efficiency of 28.9 lm/W were achieved by optimizing the recombination zone.     

Efficient green-phosphorescent light-emitting diodes based on polymeric binary-host systems

The fabrication of the green polymer light-emitting diodes based on emission from the phosphorescent molecule fac tris(2-phenylpyridine) iridium doped into a polymeric binary-host is reported. The main host used in the PLEDs was a non-conjugated polymer, poly(9-vinyl carbazole) (PVK). To realize the balanced transport of the holes and the electrons, a conjugated polymer, poly(9,9-dioctylfluorene) (PFO) was used as the assisting host. According to the experimental results, we found that the PLEDs can achieve the balance in charge transport and the recombination zone is still confined in the emissive layer by controlling the ratio of PVK to PFO. The luminous efficiency is enhanced by >40% while the external quantum efficiency can be increased by >38% in a polymeric binary-host system as compared to those of traditional device configuration, which is attributed to the balanced transport of the charged carrier.