利用电子传输层掺杂改善有机发光器件的效率

利用BCP掺杂到电子传输层Alq中,在掺杂层中阻挡了空穴的迁移,调整了空穴和电子的平衡,将激子有效地限制在发光层中发光,从而增加有机电致发光器件的效率.器件的最大电流效率在外加电压9 V时达到4.1 cd/A(掺杂浓度8%时),与一般未掺杂器件相比效率提高了2倍多.同时也减少空穴到达阴极,而减少发光淬灭.     

ITO‐free top emitting organic light emitting diodes with enhanced light out‐coupling

Bottom emitting organic light emitting diodes (OLEDs) can suffer from lower external quantum efficiencies (EQE) due to inefficient out‐coupling of the generated light. Herein, it is demonstrated that the current efficiency and EQE of red, yellow, and blue fluorescent single layer polymer OLEDs is significantly enhanced when a MoO_x(5 nm)/Ag(10 nm)/MoO_x(40 nm) stack is used as the transparent anode in a top emitting OLED structure. A maximum current efficiency and EQE of 21.2 cd/A and 6.7%, respectively, was achieved for a yellow OLED, while a blue OLED achieved a maximum of 16.5 cd/A and 10.1%, respectively. The increase in light out‐coupling from the top‐emitting OLEDs led to increase in efficiency by a factor of up to 2.2 relative to the optimised bottom emitting devices, which is the best out‐coupling reported using solution processed polymers in a simple architecture and a significant step forward for their use in large area lighting and displays.     

有机异质结连接层C60/CuPc电荷产生能力研究

有机异质结连接层因其具有良好的透光性能、制备工艺和有机电致发光器件(Organic light-emitting diodes,OLEDs)完全兼容的优点,被广泛应用于叠层OLEDs中。在叠层OLEDs中,连接层可产生电荷,其工作性能是影响叠层OLEDs性能的关键因素之一。为了获得最佳性能的有机异质结连接层,本文制备了结构为glass/ITO/tris(8-hydroxyquinoline) aluminum(Alq_3)(60 nm)/C_(60)(x nm)/CuPc(y nm)/N,N′-bis(naphthalen-1-yl)-N,N′-bis (phenyl)-be-nzidine(NPB)(40 nm)/Al (100 nm)的有机器件,直接获得了有机异质结连接层C_(60)/CuPc产生的器件电流。通过结构优化发现,结构为C_(60)(30 nm)/CuPc(10 nm)的连接层具有最强的电荷产生能力,并对最优结构连接层形成的物理机制作了合理的解释.本文获得的结果可为理解有机异质结连接层工作机理以及制备高性能叠层OLEDs提供理论基础。     

Development of organic light‐emitting diodes for electro‐optical integrated devices

Organic light‐emitting diodes (OLEDs) are discussed for electro‐optical integrated devices that are used for optical signal transmission. Organic optical devices including polymeric optical fibers are used for optical communication applications to realize polymeric electro‐optical integrated devices. The OLEDs were fabricated by vacuum process, i.e. the organic molecular beam deposition (OMBD) technique or a solution process on a polymeric or a glass substrate, for comparison. Optical signals faster than 100 MHz have been created by applying pulsed voltage directly to the OLED utilizing rubrene doped in 8‐hydoxyquinolinum aluminum (Alq₃), as an emissive layer. OLEDs fabricated by solution process utilizing rubrene doped in carrier‐transporting materials have also discussed. OLEDs utilizing polymeric materials by solution process are also fabricated and discussed. Moving‐picture signals are transmitted utilizing both vacuum‐ and solution‐processed OLEDs, respectively.     

Novel Field Emission Organic Light Emitting Diodes with Dynode

This work presents novel field emission organic light emitting diodes(FEOLEDs) with dynode,in which an organic EL light-emitting layer is used instead of an inorganic phosphor thin film in the field emission display(FED).The proposed FEOLEDs introduce field emission electrons into organic light emitting diodes(OLEDs),which exhibit a higher luminous efficiency than conventional OLED.The field emission electrons emitted from the carbon nanotubes(CNTs) cathode and to be amplified by impact the dynode in vacuum.These field emission electrons are injected into the multi-layer organic materials of OLED to increase the electron density.Additionally,the proposed FEOLED increase the luminance of OLED from 10 820 cd/m2 to 24 782 cd/m2 by raising the current density of OLED from an external electron source.The role of FEOLED is to add the quantity of electrons-holes pairs in OLED,which increase the exciton and further increase the luminous efficiency of OLED.Under the same operating current density,the FEOLED exhibits a higher luminous efficiency than that of OLED.     

Sharply directed emission in microcavity organic light-emitting diodes with a cholesteric liquid crystal film

A flexible microcavity organic light-emitting diode (OLED) was fabricated and the emitting characteristics were examined. A pair of right- and left-handed cholesteric liquid crystal (CLC) films were attached to the microcavity OLED between aluminum (Al) and silver (Ag). Sharply directed spontaneous emission was observed from microcavity OLEDs, in which a typical luminescent material, 8-hydroxyquinoline aluminum (Alq₃), with a broad emission spectrum was used for emitting layer. The introduction of the CLC film improved both the emission bandwidth and directionality, preserving the turn-on voltage and maximum brightness.     

基于垂直结构的有机光发射晶体管制备与性能研究

制备了一种有机垂直光发射晶体管, 兼具有机发光二极管的发光和晶体管的开关调节两个功能.其结构为一个有机发光单元垂直堆叠在一个电容单元上,两单元通过一个共有的源电极连在一起.当电容单元被充电时,积累在源电极的电荷能有效地调节源极与有机层之间的载流子注入势垒,从而达到控制源漏输出电流的大小,最终控制发光单元发光的强度.实验结果表明,器件可提供02 mA的输出电流,其大小可驱动发光单元发光,工作电压（开启电压）为6 V.这种垂直集成方案,实现了器件多功能化,为有机发光二极管有源矩阵驱动的实际应用提供了一种新的解决方法. 关键词： 有机光发射晶体管 垂直 电容     

一种高电流密度下效率不降低的绿光有机电致发光器件

为了提高有机电致发光器件(OLED)在高电流密度下的发光效率, 在以C545T掺杂Alq₃为发光层的有机小分子绿光器件中的发光层与电子传输层之间插入超薄LiF绝缘层.结果表明, 器件的外量子效率随着电流密度的增加始终没有降低, 直至600 mA/cm²时达到最大值 4.79%, 是相同电流密度下的参考器件的外量子效率的7倍.     

Tandem organic light-emitting diodes with an effective charge-generation connection structure

The tandem organic light-emitting diodes (OLEDs) with an effective charge-generation connection structure of Mg-doped tris(8-hydroxyquinoline) aluminum (Alq₃)/Molybdenum oxide (MoO₃)-doped 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) were presented. At a current density of 50 mA/cm², the current efficiency of the tandem OLED with two standard NPB/Alq₃ emitting units is 4.2 cd/A, which is 1.7 times greater than that of the single EL device. The tandem OLED with the similar connection structure of Mg-doped PTCDA/ MoO₃-doped PTCDA was also fabricated and the influences of the different connection units on the current efficiency of the tandem OLED were discussed as well.     

Electrical doping is paving the way for the implementation of OLEDs in consumer electronics

The great potential of organic light‐emitting diodes (OLEDs) to replace current display and lighting technologies is no longer questioned. Nevertheless, before large‐scale production can commence, considerable advances in the OLED technology are still necessary to satisfy the corresponding challenging requirements and to be competitive with firmly established alternative technologies. In this context, significant progress in diode performance, lifetime and stability is achieved by employing electrically doped charge‐transport layers. Thus, the so‐called PIN technology allows for an early, successful implementation of OLEDs in consumer applications.     

Highly efficient bipolar connecting layers for tandem organic light-emitting devices

A highly efficient tandem organic light-emitting device (OLED) has been fabricated by using an effective bipolar connecting layer structure. The connecting layers were made up of a layer of magnesium (Mg): 2,7-dipyrenyl-9,9-diphenyl fluorene (N-DPF) and a layer of tungsten trioxide (WO₃). Such a connecting layer structure permits efficient opposite holes and electrons flowing into two adjacent emitting units. The current efficiency of the two-unit tandem device can be dramatically enhanced by more than four times compared with that of the conventional single-unit device. At 60 mA/cm², the current efficiency of the tandem OLED using the connecting layers of Mg: N-DPF/WO₃ was about 8.15 cd/A. The results can be marked as a breakthrough approach to improve the current efficiency and brightness of OLEDs. Furthermore, a model of the carrier tunneling into light-emitting units is proposed based on carrier balance and field-assisted tunneling. It indicates that the connecting layer structure functions as the origin of high efficiency for the tandem OLEDs.     

Enhancement of light extraction efficiency of organic light emitting diodes using nanostructured indium tin oxide

Improved outcoupling efficiency of organic light emitting diodes (OLEDs) is demonstrated by incorporating a nanostructured indium tin oxide (NSITO) film between a conducting anode and a glass substrate. NSITO film was fabricated using rf-sputtering at oblique angle (85°). Significant reduction in refractive index and improved transmission of NSITO film was observed. OLEDs were then fabricated onto NSITO film to extract the ITO-glass waveguided modes. Extraction efficiency was enhanced by 80% without introducing any detrimental effects to operating voltage, current density, and angular invariance of emission spectra of OLEDs.     

ZnO作为电子传输层的绿光胶体CdSe量子点LED(QD-LED)的制备与表征

通过调节作为发光层的量子点的尺寸,可以制作出覆盖可见光(380～780 nm)以及近红外光谱的量子点LED(QD-LED),其光谱范围很窄且半高宽可达30 nm。然而量子点LED的寿命、亮度以及效率需要进一步提高才能满足商业化的需求。为了研究QD-LED器件的特性,本文采用523 nm波长的CdSe/ZnS核壳型量子点为发光层、poly-TPD为空穴传输层、ZnO为电子传输层,制备了绿光量子点LED,并表征了器件的特性。     

Light outcoupling efficiency enhancement in organic light emitting diodes using an organic scattering layer

Crystallized 4,7‐diphyenyl‐1,10‐phenanthroline (BPhen) films deposited by convenient vacuum thermal evaporation technique have been found to be an efficient means to extract the substrate wave guided light in organic light emitting diodes (OLEDs). The optimized BPhen film working as organic scattering layer was successfully used with OLEDs for light outcoupling efficiency improvement. Enhancement of 26%, 15% and 6% in efficiency of the blue, green and red OLEDs were obtained, respectively. The achievement was found to be advantageous in terms of simplicity of fabrication method and feasibility for large area OLED applications. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

有机电致发光器件光取出效率增强研究进展

有机电致发光器件(OLED)经过近三十年的发展,已经在照明和显示上得到一定程度的应用.OLED具有全固态、响应速度快、易于实现柔件显示等优点.由于磷光材料的应用,其内量子效率几乎达到了理论的极限值100%,但其外量子效率却只有20%左右,制约外量子效率进一步提高的主要因素是器件的光取出效率.本文从提高OLED光取出效率的方法入手,综述了国内外关于顶发射和底发射有机发光器件光取出效率增强的研究现状、最新进展及以后的研究方向.     

基于器件结构提高TADF-OLED器件的发光性能

为了提高以TADF材料作为主体、天蓝色荧光材料作为客体的混合薄膜的OLED器件光电性能,我们调整了器件结构,使主体材料发挥其优势。制备了基本结构为ITO/NPB(40 nm)/DMAC-DPS∶x%BUBD-1(40 nm)/Bphen(30 nm)/LiF(0.5 nm)/Al的OLED器件。研究了主-客体材料在不同掺杂浓度下的OLED器件的光电特性。为了提高主体材料的利用率,在空穴传输层和发光层之间加入10 nm的DMAC-DPS作为间隔层;然后,在阳极和空穴传输层之间加入HAT-CN作为空穴注入层,形成HAT-CN/NPB结构的PN结,有效降低了器件的启亮电压(2.7 V)。测量了有无HAT-CN的单空穴器件的阻抗谱。结果表明,在最佳掺杂比例(2%)下,器件的外量子效率(EQE)达到4.92%,接近荧光OLED的EQE理论极限值;加入10 nm的DMAC-DPS作为间隔层,使得器件的EQE达到5.37%;HAT-CN/NPB结构的PN结有效地降低了器件的启亮电压(2.7 V),将OLED器件的EQE提高到5.76%;HAT-CN的加入提高了器件的空穴迁移率,降低了单空穴器件的阻抗。TADF材料作为主体材料在提高OLED器件的光电性能方面具有很大的潜力。     

Thin film hexagonal gold grids as transparent conducting electrodes in organic light emitting diodes

Indium Tin Oxide (ITO) coated glass is currently the preferred transparent conducting electrode (TCE) for organic light emitting diodes (OLEDs). However, ITO has its drawbacks, not least the scarcity of Indium, high processing temperatures, and inflexibility. A number of technologies have been put forward as replacements for ITO. In this paper, an OLED based on a gold grid TCE is demonstrated, the light emission through the grid is examined, and luminance and current measurements are reported. The gold grid has a sheet resistance of 15 Ω□⁻¹ and a light transmission of 63% at 550 nm, comparable to ITO, but with advantages in terms of processing conditions and cost. The gold grid OLED has a lower turn‐on voltage (7.7 V versus 9.8 V) and achieves a luminance of 100 cdm⁻² at a lower voltage (10.9 V versus 12.4 V) than the reference ITO OLED. We discuss the lower turn‐on voltage and the uniformity of the light output through the gold grid TCE and examine the conduction mechanisms in the ITO and gold grid TCE OLEDs.     

基于超薄发光层及双极性混合间隔层的白光有机发光器件研究

本文采用非掺杂超薄发光层及双极性混合间隔层结构,获得了高效、光谱稳定的白光有机发光器件.基于单载流子器件及单色蓝光有机发光器件的研究,确定了双极性混合间隔层的最佳比例;通过瞬态光致发光寿命研究,验证了不同发光材料之间的能量传递过程;得到的三波段和四波段白光有机发光器件的最高效率分别为52 cd/A (53.5 lm/W)和13.8 cd/A (13.6 lm/W),最高外量子效率分别为17.1%和11.2%.由于发光层不同颜色之间依次的能量传递结构,三波段白光有机发光器件的亮度从465到15950 cd/m~2时,色度坐标的变化?CIE仅为(0.005, 0.001);四波段白光有机发光器件的亮度从5077到14390 cd/m~2时,色度坐标的变化?CIE为(0.023, 0.012).     

Electron-irradiated n+-Si as hole injection tunable anode of organic light-emitting diode

Traditionally, n-type silicon is not regarded as a good anode of organic light emitting diode (OLED) due to the extremely low hole concentration in it; however, when doped with Au element which acts as carrier generation centers, it can be, as shown in our previous work. In this study, we demonstrate a new kind of carrier generation centers in n⁺-type silicon, which are the defects produced by 5 MeV electron irradiation. The density of carrier generation centers in the irradiated n⁺-Si anode can be controlled by tuning the electron irradiation time, and thus hole injection current in the OLEDs with the irradiated n⁺-Si anode can be optimized, leading to their much higher maximum efficiencies than those of the OLEDs with non-irradiated n⁺-Si anode. For a green phosphorescent OLED with the irradiated n⁺-Si anode, the current efficiency and power efficiency reach up to 12.1 cd/A and 4.2 lm/W, respectively.     

典型有机发光二极管中载流子传输和复合模型

提高载流子复合效率是改善有机发光二极管(OLEDs)发光效率的重要方法。采用真空热蒸发成膜法制作了典型双层结构的OLEDs(ITO/TPD/Alq₃/Al)。二极管的性能测试结果表明器件的电流-电压关系与Fow ler-Nordheim场发射载流子注入理论符合得较好。以Fow ler-Nordheim场发射载流子的隧穿注入理论为基础,对OLEDs的电流进行理论分析和数学推导,建立典型双层结构有机发光二极管中载流子传输、复合的理论模型。以此模型为依据,对载流子注入复合进行理论分析,探究载流子注入复合的效率的表达式。在外加电压和器件材料一定下,得出了载流子复合效率与阳极区一侧积累的空穴面密度和阴极区一侧积累的电子面密度的关系表达式。