窄谱带绿色有机电致发光器件

以Tb³⁺:水杨酸(Tb³⁺:(SA)₃)为空穴传输层兼发光层、高荧光材料Alq₃为电子传输层,得到了窄谱带的绿色有机薄膜电致发光双层结构器件.实验证实,双层器件的电致发光是电荷载流子隧穿内界面(Tb³⁺:(SA)₃/Alq₃)之后分别在两有机层内的复合发光,是两有机层本征发光的叠加.其光谱随着电子传输层厚度而改变,因而减少电子传输层厚度能得到亮度高、稳     

空间电荷限制电流法测量共混体系中空穴的迁移率

载流子迁移率测量是有机半导体材料与器件研究中的重要内容之一.以聚噻吩为电子给体材料, C₆₀的衍生物为电子受体材料,制备了一种单电荷传输器件.用空间电荷限制电流法测出了不同溶剂形成的 活性层及不同温度热处理后器件中空穴的迁移率.结果表明:器件中电荷的传输J-V曲线符合Mott-Gurney方程, 不同溶剂形成活性层中空穴具有不同的迁移率,高沸点的溶剂1, 2-二氯苯形成的活性层具有较高的空穴迁移率, 热处理有利于器件中空穴迁移率的提高.同时还进一步分析了空穴迁移率变化的原因.     

芴-咔唑新型共聚物/PVK掺杂体系的电致发光特性研究

研究了新型的芴-咔唑共聚物(PFC)与聚乙烯咔唑(PVK)掺杂体系的光致发光和电致发光特性.制备了结构分别为indium-tin-oxide(ITO)/PVK:PFC/bathocuproine(BCP)/tris-(8-hydroxylquinoline)-aluminum (Alq₃) /Mg:Ag，ITO/PFC/BCP/Alq₃/Mg∶Ag和ITO/PVK/BCP/Alq₃/Mg∶Ag的三种有机电致发光器件.对器件的光电特性进行了测试.结果表明，掺杂体系中的PVK有效地抑制了固态膜中PFC激基缔合物的形成.掺杂器件在不同的外加电场作用下发生发光层位置的移动，通过调节外加电场，可以获得从绿光到蓝光的可见光发射.当外加电压大于7V时，掺杂器件的蓝色发光亮度达到1650cd/m²，推测其中可能存在从PVK到PFC的能量传递过程.     

使用不同阴极缓冲层提升性能的反型有机太阳能电池

使用含Al_q3、Bphen、BCP、HATNA和Cs₂CO₃作为阴极缓冲层,制备了基于SubPc和C₆₀的反型平面异质结有机太阳能电池. 比较了有机阴极缓冲层的最低未占有分子轨道和电子迁移率对有机太阳能电池性能的影响. 结果显示,Al_q3、Bphen和HATNA能够大幅度提升器件的性能. 使用退火过后的HATNA作为阴极缓冲层获得了最高的效率,比没有阴极缓冲层的器件提升了7倍. 另外,使用空间电荷限制电流理论进行仿真的结果表明,通过加入HATNA作阴极缓冲层,反型有机太阳能电池结构中处于有机/电极界面处的肖特基势垒降低了27%.     

Li掺杂8-羟基喹啉铝的密度泛函理论研究

采用密度泛函理论研究了Li原子掺杂8-羟基喹啉铝(Alq₃)分子的几何构型、 前线分子轨道及电子转移特性. 研究结果表明, Li原子掺杂Alq₃后, Li原子与Alq₃的O, N原子键合, 形成电子转移复合物. Li原子将部分电子转移到Alq₃的吡啶环上, 在Alq₃的带隙内形成施主能级, 这种n型掺杂结构有效地提高了电子的传输效率; 但过多的Li原子的掺杂会使Alq₃分解, 从而减弱其电子传输能力. 为使Alq₃的电子传输能力达到最高, Li原子的掺杂应保持在2:1左右的比例.     

Organic Photovoltaic Cells with Improved Performance Using Bathophenanthroline as a Buffer Layer

采用Bphen作为缓冲层,研究Bphen处在电子受体材料C₆₀和阴极Ag之间对有机薄膜光伏电池(OPV)性能的影响．通过引入2.5nm厚的Bphen,在100 mW/cm²光照下,CuPc/C₆₀结构的器件效率从0.87%提高到2.25%． 对光生电流-电压的分析表明,Bphen缓冲层可以有效的提高电子从C₆₀层向Ag阴极的传输能力和平衡器件中载流子的传输能力．系统研究了Bphen厚度对OPV器件性能的影响,发现随着Bphen厚度的增加,电导率的降低是限制器件性能的主要原因．此外,采用紫外-可见光分光光度计测试了器件的吸收光谱,发现Bphen缓冲层可以增强CuPc/C₆₀的光吸收能力．     

磁场作用下的有机电致发光

分别制备了荧光器件ITO/NPB/Alq₃/LiF/Al和磷光器件ITO/NPB /CBP: Ir（ppy）₃/BCP/Alq₃/LiF/Al, 测试了50 mT磁场作用下器件的I-V和L-V特性. 与零磁场相比荧光器件和磷光器件的效率分别增加了44%和7%. 从有机电致发光的机制出发对该现象进行了解释, 认为外加磁场可以使三重态激子发生塞曼分裂, 进而在荧光器件中引起了三重态激子T     

4,4′,4″-三(N-3-甲基苯基-N-苯基氨基)三苯胺掺杂MoOx作为空穴传输层对有机太阳电池性能的影响

通过采用4,4′,4″-三(N-3-甲基苯基-N-苯基氨基)三苯胺 (m-MTDATA)掺入MoO_x作为器件的空穴传输层来提高酞菁铜(CuPc)/C₆₀小分子 有机太阳电池的效率. 采用真空蒸镀的方法制备了一系列器件, 其中结构为铟锡氧化物 (ITO)/m-MTDATA:MoO_x(3:1)(30 nm)/CuPc(20 nm)/C₆₀(40 nm)/4,7-二苯 基-1,10-菲罗啉 (Bphen)(8 nm)/LiF(0.8 nm)/Al(100 nm)的器件, 在AM1.5 (100 mW/cm²)模拟太阳光的照射条件下, 开路电压V_oc=0.40 V, 短路电流J_sc=6.59 mA/cm², 填充因子为0.55, 光电转换效率达1.46%, 比没有空穴传输层的器件ITO/CuPc(20 nm)/C₆₀(40 nm)/Bphen(8 nm)/LiF(0.8 nm)/Al(100 nm) 光电转换效率提高了38%. 研究表明, 加入m-MTDATA:MoO_x(3:1)(30 nm)空穴传输层减小了有机层和ITO电极之间的接触电阻, 从而减小了整个器件的串联电阻, 提高了器件的光电转换效率.     

富勒烯掺杂NPB空穴传输层的有机电致发光器件

报道了不同掺杂浓度NPB：C₆₀（富勒烯）作为空穴传输层对有机电致发光器件性能的影响.采用真空热蒸镀方法,制作了ITO/ NPB：C₆₀ （x % ）/Alq₃/LiF/Mg:Ag结构的四种有机电致发光器件.当NPB：C₆₀的掺杂浓度是15％时,器件的启亮电压是4 V,最大亮度是11000 cd/m².然而,当NPB：C₆₀的掺杂浓度是20％时,器件的最大亮度降     

栅漏间表面外延层对4H-SiC功率MESFET击穿 特性的改善机理与结构优化

本文提出了一种带栅漏间表面p型外延层的新型MESFET结构并整合了能精确描述4H-SiC MESFET工作机理的数值模型,模型综合考虑了高场载流子饱和、雪崩碰撞离化以及电场调制等效应. 利用所建模型分析了表面外延层对器件沟道表面电场分布的改善作用,并采用突变结近似法对p型外延层参数与器件输出电流(I_ds)和击穿电压(V_B)的关系进行了研究.结果表明,通过在常规MESFET漏端处引入新的电场峰来降低栅极边缘的强电场峰并在栅漏之间的沟道表面引入p-n结内建电场进一步降低电场峰值,改善了表面电场沿电流方向的分布.通过与常规结构以及场板结构SiC MESFET的特性对比表明,本文提出的结构可以明显改善SiC MESFET的功率特性.此外,针对文中给定的器件结构,获得了优化的设计方案,选择p型外延层厚度为0.12 μupm,掺杂浓度为5× 10¹⁵ cm^-3,可使器件的V_B提高33%而保持I_ds基本不变.     

Efficient organic light-emitting diodes with zinc acetate as an effective electron injection layer

We report on the fabrication of organic light-emitting diodes (OLEDs) using a zinc acetate ((CH₃COO)₂Zn) layer as the cathode buffer layer. The results show that the device containing a (CH₃COO)₂Zn interlayer shows improved luminance and efficiency due to the Zn–N bond formation resulting in the occurrence of Alq₃ anion and also due to the band bending at the Alq₃/Al interface, which is beneficial to electron injection by lowering electron injection barrier. And the devices with structured cathodes (CH₃COO)₂Zn/LiF/Al and LiF/(CH₃COO)₂Zn/Al have a higher luminance and efficiency than the LiF/Al cathode-based device.     

Enhanced electron injection in organic light-emitting devices using Al/LiF electrodes

The temperature dependence of the current-voltage-luminescence characteristics in organic light-emitting diodes (OLEDs) with varying thickness of LiF layers are studied to understand the mechanism of the enhanced electron injection by inserting a thin insulating LiF layer at the tris(8-hydroxyquinoline) aluminum (Alq₃)–Al interfaces. At room temperature, the LiF/Al cathode enhances the electron injection and the quantum efficiency (QE) of the electroluminescence (EL), implying that the LiF thin layer lowers the electron-injection barrier. However, at low temperatures it is observed that the injection-limited current dominates and the barrier height for the electron injection in the device with LiF/Al appears to be similar with the Al only device. Thus, our results suggest that at low temperatures the insertion of LiF does not cause a significant band bending of Alq₃ or reduction of the Al work function.     

Investigation of an efficient YbF3/Al cathode for tris-(8-hydroxyquinoline)aluminum-based small molecular organic light-emitting diodes

Efficient tris-(8-hydroxyquinoline)aluminum (Alq₃)-based organic light-emitting diodes (OLEDs) using YbF₃ as the electron injection layer have been investigated. With an YbF₃ (3.0 nm)/Al cathode, the device with Alq₃ as the emitting layer achieved a better performance than the control device with a LiF (0.5 nm)/Al cathode. The release of the low-work-function metal Yb is responsible for the performance enhancement. From the analysis by atomic force spectroscopy and X-ray photoemission spectroscopy, it is observed that the Alq₃-cathode interface could be well covered by YbF₃ at an optimum thickness of 3.0 nm, which helps to prevent the contact between Alq₃ and Al, and to reduce the destruction of Alq₃ by Al.     

室温下磁场对基于Alq3的有机电致发光器件的影响

制备了ITO/NPB/LiF/Alq₃/LiF/Al的器件,测量了该组器件效率和亮度的磁效应.结果表明,在50 mT磁场中,当LiF缓冲层厚度为0.8 nm时,器件的效率最大增加了12.4%,磁致亮度最大变化率17%.同时,制备的磷光器件ITO/NPB/LiF/CBP:6 wt% Ir(ppy)₃/BCP/Alq₃/ LiF/Al,在50mT磁场作用下,当LiF缓冲层的厚度为0.8 nm时,器件的效率最大增加12.1%.在Alq_{3 关键词： 有机发光 磁场 效率 磁致亮度}     

Influence of small-molecule material on performance of polymer solar cells based on MEH-PPV:PCBM blend

In this work,the influence of a small-molecule material,tris(8-hydroxyquinoline) aluminum (Alq 3),on bulk het-erojunction (BHJ) polymer solar cells (PSCs) is investigated in devices based on the blend of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and [6,6]-phenyl-C 61-butyric acid methyl ester (PCBM).By dop-ing Alq 3 into MEH-PPV:PCBM solution,the number of MEH-PPV excitons can be effectively increased due to the energy transfer from Alq 3 to MEH-PPV,which probably induces the increase of photocurrent generated by excitons dissociation.However,the low carrier mobility of Alq 3 is detrimental to the efficient charge transport,thereby blocking the charge collection by the respective electrodes.The balance between photon absorption and charge transport in the active layer plays a key role in the performance of PSCs.For the case of 5 wt.% Alq 3 doping,the device performance is deteriorated rather than improved as compared with that of the undoped device.On the other hand,we adopt Alq 3 as a buffer layer instead of commonly used LiF.All the photovoltaic parameters are improved,yielding an 80% increase in power conversion efficiency (PCE) at the optimum thickness (1 nm) as compared with that of the device without any buffer layer.Even for the 5 wt.% Alq 3 doped device,the PCE has a slight enhancement compared with that of the standard device after modification with 1 nm (or 2 nm) thermally evaporated Alq 3.The performance deterioration of Alq 3-doped devices can be explained by the low solubility of Alq 3,which probably deteriorates the bicontinuous D-A network morphology;while the performance improvement of the devices with Alq 3 as a buffer layer is attributed to the increased light harvesting,as well as blocking the hole leakage from MEH-PPV to the aluminum (Al) electrode due to the lower highest occupied molecular orbital (HOMO) level of Alq 3 compared with that of MEH-PPV.     

Blocking of interfacial diffusion at Ag/Alq3 by LiF

X-ray photoelectron spectroscopy has been applied to interface studies of Ag/tris-(8-hydroxyquinoline) aluminum (Alq₃) and Ag/LiF/Alq₃. For Ag/Alq₃, diffusion of Ag atoms into the Alq₃ layer occurs immediately after the adhesion of the metal onto the organic layer and the process lasts several hours. Insertion of a monolayer-thick LiF buffer at the interface can effectively block the diffusion process. This is quite different from what is observed from Al/LiF/Alq₃, where Al penetrates into the LiF layer as deep as several nanometers. It is thus concluded that the LiF buffer may play different roles in Ag/LiF/Alq₃ and Al/LiF/Alq₃ and hence different mechanisms may dominate in the two cases for the enhanced carrier injection observed.     

High-efficiency Simple Structure White Organic Light-emitting Devices Based on Rubrene Ultrathin Layer

White organic light-emitting devices (WOLEDs) were fabricated with an ultrathin layer of rubrene inserted between NPB and TPBI. With a simple three-layer structure of ITO/NPB(50 nm)/rubrene(0.1 nm)/TPBI(50 nm)/LiF/Al, a white light with CIE coordinates of (0.31, 0.30) were generated. The device gave a maximum luminance efficiency of 2.04 lm/W at 5 V. Furthermore, with a multilayer structure of ITO/m-MTDATA(30 nm)/NPB(20 nm)/rubrene(0.1 nm)/TPBI(40 nm)/Alq₃(10 nm)/LiF/Al, the device reached a maximum luminance efficiency of 4.29 lm/W at 4 V and the luminance could exceed 10 000 cd/m² at 10 V.     

Effect of dye dopants in poly(methylphenyl silane) light-emitting devices

To investigate the inter-molecular energy transfer between polysilane and dye dopants, poly(methylphenylsilane)(PMPS) was used as a host material and perylene as the blue dopant. The structure of the devices is indium–tin oxide (ITO)/PEDOT:PSS(30 nm)/PMPS:perylene(dye dopant 0.1–1.0 mol%)(60 nm)/Alq₃(20 nm)/LiF(0.5 nm)/Al(100 nm). Poly(3,4-ethylenedioxythiophene) (PEDOT):poly(4-styrenesulfonate) (PSS) is used as a buffer layer, tris(8-hydroxyquinoline)aluminum (Alq₃) as hole transporting layer, LiF as hole injection layer. The device shows a luminance 810 cd/m² at current density of 28 mA/cm², luminous efficiency of 0.14 lm/W. The external quantum efficiency (EQE) is about 0.5% and EQE increased up to 0.52% by doping with single wall carbon nanotubes (SWNT) into the emissive layer. We found an efficient inter-molecular energy transfer from polysilane to dye dopants. Furthermore, using the polysilane and energy-matched dye dopants enable to fabricate the electroluminescence devices through wet processes.     

Highly efficient and stable organic light-emitting diode by balancing drift current of charge

Highly efficient and stable OLED device in which hole-drift current and electron-drift current are balanced was fabricated. Drift current characteristics according to the thickness of organic layer were examined using the device with ITO/m-MTDATA/NPB/Al structure that can only move the hole and the device with Al/LiF/Alq₃/LiF/Al structure that can only move the electron. Using the result of such examination, green device with balanced drift current was produced. Device with the structure of m-MTDATA (80 nm)/NPB (20 nm)/C-545T (3%) doped Alq₃ (5 nm)/Alq₃ (59 nm)/LiF (1 nm)/Al (200 nm) showed color purity of (0.309, 0.643) and high efficiency of 7.0 lm/W (14.4 cd/A). Most of light emission was observed inside the green emitting layer. Through the result of EL spectrum for the device also including red emitting layer, same result could be obtained. The device with balanced drift current also showed half life-time of 175 h for initial luminance of 3000 cd/m², which is more stable in comparison to the device without balanced drift current.     

The mechanism of efficiency enhancement with proper thickness of DPVBi layer for blue organic light-emitting devices (BOLED)

We report on the fabrication of blue organic light-emitting devices (BOLEDs) with structure: ITO/NPB/DPVBi/Alq₃/LiF/Al. The hole-blocking effect in NPB/DPVBi interface was indirectly demonstrated and deduced by inserting DCJTB layer. In addition, the effect of the device with better J–V characteristics because of the extra DCJTB layer is discussed as well. However, the performance of devices was investigated with various thicknesses of DPVBi layer. The result shows that the device with proper thickness of DPVBi layer generating better electron injection enhances efficiency and luminance for BOLED.