新型TPBI/Ag阴极结构的红色有机发光二极管

采用可溶液加工的小分子红光材料2为发光层（EML）,制备了不同阴极结构的系列电致发光器件.结果表明,空穴阻挡层（HBL）TPBI的引入能有效降低高功函数（Al, Ag, Au）金属阴极的电子注入势垒,显著改善器件发光效率,与传统阴极结构（Ba/Al）比较,采用TPBI/Ag阴极结构的器件外量子效率提高了57%,主要原因是TPBI/Ag阴极界面形成较低的电子注入势垒,有利于电子注入,使器件发光效率明显提高. 关键词： 电致发光 电子注入 阻挡层 高功函数金属阴极     

倒置器件结构及局域等离子体效应对CdSe量子点LED发光性能的改进

研究了倒置器件结构以及CdSe量子点发光材料与金属纳米粒子之间的相互作用对量子点的电致发光性能的影响。利用TiO₂作为电子传输/注入层,成功地制备了倒置结构的量子点电致发光器件。通过对单载流子器件电压-电流特性的分析,证明了ITO作为阴极到TiO₂的电子注入特性与Al作为阴极时的效果几乎相同。观察到金属纳米粒子产生的局域等离子体效应提高了器件的效率,使得效率随电流增大而降低的速度明显减小。在电流密度为200 mA/cm²时,电致发光器件的效率大约提高了42%。     

柠檬酸钾电子注入层对有机电致发光器件的影响

使用柠檬酸钾(C₆H₅K₃O₇)作为电子注入材料,制备了多层有机电致发光器件。当柠檬酸钾阴极修饰层厚度为0.5 nm时,得到3.6 cd/A 的发光效率,高于0.5 nm LiF作阴极修饰层时的发光效率(2.5 cd/A) 。器件的开启电压相比0.5 nm LiF作阴极修饰的器件降低了0.5 V。实验结果表明,柠檬酸钾(C₆H₅K₃O₇)是一种良好的电子注入材料。     

CsF/Al阴极对提高芴基饱和红光器件性能的研究

从聚合物/电极界面修饰的角度对基于饱和红光聚合物PFO-SeBT(9,9-二辛基芴与4,7-二硒吩-2,1,3-苯并噻二唑的无规共聚物)的发光二极管的性能进行了改进，通过采用CsF/Al阴极并优化CsF的厚度以及在PFO-SeBT1/阳极界面插入聚乙烯基咔唑(PVK)层，使器件的最大电致发光外量子效率达到1.79%，比采用低功函数的金属Ba/Al阴极器件的效率提高了两倍多.器件的性能得以改善的原因是CsF/Al阴极能有效提高电子注入能力以及PVK层对电子的阻挡作用. 关键词： 聚合物发光二极管 聚合物/电极界面 CsF/Al阴极 电子注入     

多层结构的阴极修饰层对有机电致发光器件的性能改善

为提高有机电致发光器件（OLEDs）的阴极电子注入效率,我们设计了新型的阴极杂化修饰层,其结构为Bphen∶LiF/Al/MoO₃,将其应用到器件ITO/NPB/Alq₃/Al中,参考器件的电子注入层选用传统材料LiF。实验研究表明,与传统的阴极修饰层LiF相比,基于这种杂化结构的阴极修饰层非常有效。测试了器件的电致发光光谱（EL谱）,其峰值位于534 nm,发光来自于Alq₃,实验中我们可以观察到明亮的绿色发光。将其与传统参考器件的EL谱进行对比,在电流密度40 mA·cm-2下,两个器件的电致发光光谱是一致的。在0～100 mA·cm-2范围内,对器件的EL谱进行了测试。实验结果表明,随着电流密度的增加,器件的发光增强,但是EL谱的形状和谱峰的位置是固定不变的。与参考器件对比,基于杂化修饰层的器件的发光性能更好。研究表明,杂化修饰层的最佳参数为Bphen∶LiF(5 nm; 6%)/Al(1 nm)/MoO₃(5 nm),在测试范围内,器件的最大电流效率和最大功率效率分别为4.28 cd·A-1和2.19 lm·W-1,相比参考器件提高了25.5%和23.7%。器件的电流密度-电压特性曲线表明阴极杂化修饰层可以增强电子的注入,使器件中的载流子更加平衡,从而提高了器件的发光性能。从两个角度对器件效率的增强进行了理论方面的论证。一方面利用阴极杂化修饰层的作用机制来解释。在HML中,LiF能填充Bphen的电子陷阱,增强电流的注入,同时HML也能限制空穴的传输,减小空穴电流。另一方面从电荷平衡因子的角度,HML增强了电子的注入,使得器件的电荷平衡因子增大,空穴和电子的平衡性更好。实验研究表明,阴极杂化修饰层很好地增强了器件的效率。     

有机薄膜电致发光器件载流子注入和传输性质的研究

制备了不同电极、不同厚度、以8-羟基喹啉铝螯合物(Alq3)为发光层的有机薄膜电致发光(TFEL)器件。分析了它们的电流密度-电压关系。不同阳极器件的电流变化很大,而改变阴极时电流密度的变化较小,说明电流以空穴为主。根据不同阴极器件的电致发光效率的比较,说明电子是决定器件电致发光效率的少数载流子。从不同厚度的器件的结果讨论了载流子的传输性质,认为在ITO/Alq3/Al器件中的电流符合陷阱限制的空间电荷电流.     

9,9-二辛基聚芴-苯并噻二唑交替共聚物的绿光偏振电致发光

通过缩聚法合成了绿光9,9-二辛基聚芴-苯并噻二唑交替共聚物（PFBT）.该聚合物在一定温度范围内形成向列液晶态,利用其在定向层上的有序排列,实现了峰值发光波长为550 nm的偏振电致发光.采用摩擦后的空穴注入层聚（3,4-乙撑二氧噻吩）∶聚（苯乙烯磺酸）（PEDOT:PSS）作为定向层,通过偏振紫外可见吸收光谱和偏振光致发光谱,研究了聚合物分子在薄膜平面内的单轴取向特性,计算得到薄膜的有序参数为075.制备了结构为ITO/PEDOT:PSS/PFBT/LiF/Al的聚合物电致发光器件,工作电压为15 V时,电致发光偏振率达到4,亮度和流明效率分别为450 cd/m²和021 cd/A. 关键词： 偏振发光 交替共聚物 聚合物电致发光器件     

SiO2/C9-PPV异质结中类阴极射线发光及有机电致发光的交互增强

用夹在两层SiO2之间的发光聚合物C9-PPV作成器件，在交流电激发下得到了超出有机电致发光黄绿色发光的蓝色发光.通过对器件光学特性的研究，发现这种发光源于SiO2中加速电子直接碰撞激发有机发光层而引起的类阴极射线发光.使用非对称结构，得到了类阴极射线发光与有机电致发光相互增强的混合发光. 关键词： 混合发光 类阴极射线发光 有机电致发光     

利用8-羟基喹啉锂作电子注入层以提高有机发光器件的发光效率

8-羟基喹啉锂用作有机电致发光器件的电子注入层能够提高阴极功函数,进而提高器件的发光效率。10的Liq薄膜足以降低有机电致发光器件中的开启电压并能有效提高器件效率,该现象可与LiF/Al作阴极的器件性能相比拟。利用不同阴极材料制作器件,讨论了8-羟基喹啉锂的电子注入机制,发现把Liq薄膜引入到Alq3和不同阴极之间后,器件的电流密度与所用阴极材料的种类无关。为了讨论电子在分界面上注入势垒的变化情况,对器件进行饱和光伏测试。测试发现Alq3/Liq/Al的分界面上真空能级的移动降低了电子注入势垒。推测此现象是由于在界面上形成了强偶极子,这也可能是有机电致发光器件中电子注入效率提高的机理之一。     

Poly ∶ DCJTB 为功能层LEC器件的能量传递

在有机发光器件中,掺杂染料分子是改变发光颜色,提高发光性能的有利手段。在掺杂体系中,主体材料向掺杂剂的能量传递是主要的激发态弛豫过程。在LEC器件中,利用掺杂手段改变发光颜色的方法报道很少。研究了以发射绿光(峰值550 nm)的共聚物Poly 中掺杂DCJTB作为功能层的LEC器件的发光特性。器件的结构为ITO/Poly ∶ DCJTB+PEO+LiCF₃SO₃/Al。共聚物的光致发光光谱几乎覆盖了整个DCJTB吸收光谱的范围,满足能量传递的要求。通过光致发光与电致发光光谱的研究,发现掺杂后的薄膜不论是光致发光还是电致发光,都以DCJTB的发射为主,说明二者之间的确存在能量传递。     

Ring of C60 polymers formed by electron or hole injection from a scanning tunneling microscope tip

Carrier (electron or hole) injection from a scanning tunneling microscope tip causes various surface modifications on the molecular scale. We report that injection into C60 close-packed layers forms a ring-shaped distribution of C60 polymers. This can be explained on the basis of the radial propagation and energy dissipation of carriers. Subsequent electron or hole injections enlarge the ring, showing that both carriers can induce both polymerization and depolymerization. Furthermore, we demonstrate visualization of carrier scattering by injecting carriers into C60 layers with grain boundaries.     

杂质离子对有机共轭聚合物中极化子动力学性质的影响

基于一维紧束缚Su-Schrieffer-Heeger模型, 采用分子动力学方法, 讨论了杂质势的强度和杂质之间的距离对电子和空穴极化子动力学性质的影响. 研究结果表明: 1)当杂质势强度保持不变时, 两杂质离子之间的距离(d)在2-16个晶格常数变化时, 电子极化子的平均速度大于空穴极化子的平均速度, 这是由于电子、空穴极化子与杂质势的库仑作用不同而产生的差异, 同时极化子的平均速度随d的增加而增大; 若继续增加杂质离子之间的距离, 电子和空穴极化子的平均速度几乎保持不变, 仅有一些微小的振荡, 这是由于不同距离的杂质离子对电子和空穴极化子产生的势垒或势阱的叠加效果不同而引起的; 2)保持两杂质离子之间的距离不变时, 随着杂质势强度的增大, 电子和空穴极化子的平均速度均减小, 且空穴极化子的平均速度减小趋势更明显.     

新型含咔唑聚芴类共轭聚电解质及其前驱体的合成与光电性能

采用Suzuki偶合反应成功地合成了一系列在主链上具有不同含量苯并噻二唑单元的聚咔唑和含胺基芴的衍生物:聚[3,6-(N-(2-乙基己基))咔唑-2,1,3-苯并噻二唑-9,9-双(N,N-二甲基胺丙基)芴](PCzN-BTDZ);通过对所得聚合物的季铵盐化后处理得到了其相应的聚电解质衍生物:聚[3,6-(N-(2-乙基己基))咔唑-2,1,3-苯并噻二唑-9,9-(双(3′-(N,N-二甲基)-N-乙基铵)丙基)芴]二溴(PCzNBr-BTDZ)。通过对它们的电致发光性能的研究,发现所有的聚合物用高功函数铝作阴极的器件具有和用钡/铝作阴极的器件相近的发光性能,说明这类聚合物具有良好的电子注入性能。不同比例的2,1,3-苯并噻二唑(BTDZ)的引入使聚合物中发生有效的能量转移,调节了聚合物的发光颜色;同时也提高了聚合物的器件性能。其中聚合物PCzN-BTDZ1在器件结构为ITO/PEDOT/PVK/Polymer/BaAl时的效率达0.99%,高于PCzN在相同器件结构时的效率(0.14%)。     

Influence of Blocking Interlayer in Blue Organic Light-Emitting Diodes with Different Thicknesses of Emitting Layer and Interlayer

A series of blue organic light-emitting diodes with electron or hole blocking interlayer are fabricated.Different structures of blocking interlayers can influence the position of the recombination zone due to the fact that they confine carriers in different ways.We find that the double hole blocking interlayer structure can balance carrier injection more effectively.Its power and current efficiency are more stable and the current efficiency value is30.2cd/A at 1000cd/m2.Decreasing the thicknesses of the emitting layer and interlayers is in favor of the power efficiency.The performance of the device is also affected by changing the interlayer position when we use hole and electron blocking material as interlayers simultaneously.     

Organic polymer p-n heterostructures for optoelectronics

The photovoltaic effect due to the photogeneration of charge carriers at the interface in organic polymeric p-n-heterostructures based on the developed composites with hole (doped polyimides, conjugated polymers) and electron (doped polyetherimides and carbazolyl-containing polymers) conduction was observed and studied. The best performance was observed for heterostructures with diffuse and developed (bulk) interface. The maximum energy conversion efficiency was found to be 0.5% at λ = 400–650 nm. Components with enhanced photo and thermal stability were used. A weak photovoltaic effect was observed for heterostructures based on conjugated polymers (with a sharp interface). In this case, the rectification (diode) effect was observed for both dark current and photocurrent due to dark and photo injection of carriers from the electrodes at bias voltages across the cell above the injection threshold (V > V _i ). This conclusion is supported by the observation of recombination electroluminescence of the dopant in the n-layer, indicating a full or partial recombination of carriers at the interface. At V < V _i , photocurrent under reverse bias (+A1, ?ITO) is significantly higher than that under forward bias due to an efficient photogeneration of carriers at the interface and separate transport thereof. A sensitivity of about 100 mA/W at λ = 400–500 nm was reached.     

利用山形空穴存储层结构对深紫外激光二极管的性能优化

为了有效提高深紫外激光二极管的空穴注入效率和减少电子泄露,优化其性能,设计出了在基础矩形空穴存储层结构上改进后的山形空穴存储层和倒山形空穴存储层。使用Crosslight软件模拟仿真倒山形和山形空穴存储层结构的电子浓度、电子电流密度、能带图以及P-I特性曲线。结果显示山形空穴存储层激光器的光学和电学性能优于矩形和倒山形激光器,因此山形空穴存储层激光器能有效地增加有源区空穴注入和减少电子泄露,提高有源区载流子浓度和辐射复合速率,实现了激光器优越的光电性能。     

Novel transparent Yb-based cathodes for top-emitting organic light emitting devices with high performance

We have studied three kinds of transparent low-work-function Yb-based cathodes for the top-emitting organic light emitting devices (TEOLEDs) with a structure of ITO/NPB/Alq₃/cathodes and compared them with each other. For the Yb/Au cathodes, a series of Yb layers with various thicknesses have been tested and it is found that the Yb layer with a thickness of 4 nm is the optimum one. The Yb:Au (19 nm) and Yb:Ag (19 nm) co-evaporation cathodes possess very high transmittance but relative poor electron injection; whilst the Yb (4 nm)/Au (15 nm) cathode possess a little lower transmittance but much improved electron injection and the TEOLED with this cathode has the highest power efficiency among the TEOLEDs with the three kinds of Yb-based cathodes mentioned above.     

Hollow Cathode Effect with Double Axial Electron Injection

The paper presents a new type of HCE glow discharge obtained with double plane-conical cathodes. The two identical cathodes are tronconical and screened with 1 mm² mailed wire net with a 3.5 mm diameter central washer each. The discharge is obtained between the two cathodes and a ring shaped anode equally distant from both. Optimum intercathodic span is 4 mm, allowing for maximum amplifications at the optimum pressure values for the two gases. Employed helium and argon are spectral pure. At the given distance and depending on voltage and gas pressure, a double axial electron self injection cathode effect is obtained between the electrodes, consisting of very large increase of current and radiations.     

Nonadiabatic dynamics of electron injection into organic molecules

We numerically investigate the injection process of electrons from metal electrodes to one-dimensional organic molecules by combining the extended Su-Schrieffer-Heeger (SSH) model with a nonadiabatic dynamics method. It is found that a match between the Fermi level of electrodes and the highest occupied molecular orbital (HOMO) or the lowest unoccupied molecular orbital (LUMO) of organic molecules can be greatly affected by the length of the organic chains, which has a great impact on electron injection. The correlation between oligomers and electrodes is found to open more efficient channels for electron injection as compared with that in polymer/electrode structures. For oligomer/electrode structures, we show that the Schottky barrier essentially does not affect the electron injection as the electrode work function is smaller than a critical value. This means that the Schottky barrier is pinned for a small work-function electrode. For polymer/electrode structures, we find that it is possible for the Fermi level of electrodes to be pinned to the polaronic level. The condition under which the Fermi level of electrodes exceeds the polaronic level of polymers is shown to not always lead to spontaneous electron transfer from electrodes to polymers.     

Simulation study of blue InGaN multiple quantum well light-emitting diodes with different hole injection layers

InGaN-based light-emitting diodes with p-GaN and p-AlGaN hole injection layers are numerically studied using the APSYS simulation software.The simulation results indicate that light-emitting diodes with p-AlGaN hole injection layers show superior optical and electrical performance,such as an increase in light output power,a reduction in current leakage and alleviation of efficiency droop.These improvements can be attributed to the p-AlGaN serving as hole injection layers,which can alleviate the band bending induced by the polarization field,thereby improving both the hole injection efficiency and the electron blocking efficiency.