VOx作空穴注入层的低启亮电压有机发光二极管

W增加到2.63 lm/W.此外,对VOx厚度分别为10,20和30 nm的三组器件进行了对比,结果显示器件性能基本一致.     

空穴注入层技术在聚合体OLED器件中的重要性

空穴注入层技术可降低OLED成本和提高其生产效率,是使柔性OLED显示成为商品化的一个重要因素。     

以聚乙烯亚胺作为电子注入层的聚合物发光器件特性研究

在传统结构与倒置结构的有机发光二极管(LED)的聚合物发光层和阴极之间加入聚乙烯亚胺(PEIE)层能够显著地提高器件的发光效率。通过采用不同厚度的PEIE层的器件发光特性研究表明:PEIE层作为电子注入层(EIL)/空穴阻挡层(HBL)来平衡器件中的电子和空穴浓度,这主要来源于PEIE作为界面偶极层,能有效地降低阴极与发光层之间的电子注入势垒。     

衬底热空穴注入下的薄栅氧化层击穿特性

利用衬底热空穴(SHH)注入技术,分别定量研究了热电子和空穴注入对薄栅氧化层击穿的影响,讨论了不同应力条件下的阈值电压变化.阈值电压的漂移表明是正电荷陷入氧化层中,而热电子的存在是氧化层击穿的必要条件.把阳极空穴注入模型和电子陷阱产生模型统一起来,提出了薄栅氧化层的击穿是与电子导致的空穴陷阱相关的.研究结果表明薄栅氧化层击穿的限制因素依赖于注入热电子量和空穴量的平衡.认为栅氧化层的击穿是一个两步过程.第一步是注入的热电子打断Si一O键,产生悬挂键充当空穴陷阱中心,第二步是空穴被陷阱俘获,在氧化层中产生导电通路,薄栅氧化层的击穿是在注入的热电子和空穴的共同作用下发生的.     

衬底热空穴注入下的薄栅氧化层击穿特性

利用衬底热空穴 (SHH)注入技术 ,分别定量研究了热电子和空穴注入对薄栅氧化层击穿的影响 ,讨论了不同应力条件下的阈值电压变化 .阈值电压的漂移表明是正电荷陷入氧化层中 ,而热电子的存在是氧化层击穿的必要条件 .把阳极空穴注入模型和电子陷阱产生模型统一起来 ,提出了薄栅氧化层的击穿是与电子导致的空穴陷阱相关的 .研究结果表明薄栅氧化层击穿的限制因素依赖于注入热电子量和空穴量的平衡 .认为栅氧化层的击穿是一个两步过程 .第一步是注入的热电子打断 Si— O键 ,产生悬挂键充当空穴陷阱中心 ,第二步是空穴被陷阱俘获 ,在氧化层中产生导电通路     

双空穴注入层对有机电致蓝光器件性能的改善

CuI/CuPc被采用作为有机电致蓝光CBP:BCzVBi器件 的双空穴注入层。采用双空穴注入层后使得CBP:BCzVBi蓝光器件的启亮电压降低至 3.4 V,较采用CuPc单空穴注入层的CBP:BCzVBi蓝光器件低0.4 V。在驱动电流20 mA/cm²的情况下,与单空穴注入层器件 相比,采用该双空穴注入层结构使得器件电流效率提升约19%,亮度 增加约17%,驱动电压降低0.9 V。采用Fowler -Nordheim (F-N)隧穿注入理论对器件空穴注入电流的影响因素进行了分析,发现双空穴 注入层形成的能级台阶可以有效地改善发光器件的空穴注入效率,进而起到改善器件发光电 流效率和降低驱动电压的目的。     

利用新型的空穴注入层材料提高有机发光器件性能

研究使用新材料2-TNATA作空穴注入层制备OLED,发现空穴注入层厚度的最佳参数为35 nm,器件的发光光谱随空穴注入层厚度并不发生显著变化,微腔作用对发光光谱的影响基本可以忽略.并将2-TNATA作为空穴注入层的器件同CuPc制作的器件进行了对比,发现使用2-TNATA能获得更佳的器件性能.     

不同空穴注入层对有机电致发光器件的影响

研究了不同空穴注入层对有机电致发光器件性能的影响,结果表明,由于m-MTDATA具有良好的成膜性,以及空穴注入能力,可以改善空穴向发光层的注入,有助于提高器件的效率。     

新型双空穴注入型高效有机电致发光二极管

采用一种新型有机电致发光二极管（OLED）的阳极结构,在玻璃衬底上以半透明的A1膜为出光面,通过在空穴注入层（HIL）和空穴传输层（HTL）中间插入MoOa层,制备了底发射OLED。制备的器件结构为Glass／Al（15nm）／HAT—CN（IOnm）／M003（30nm）／NPB（30nm）／Alq3（60nm）／B...     

空穴注入层2T-NATA对OLED器件性能的影响

为了提高有机电致发光器件OLED的发光效率,引入2T-NATA作为空穴注入层,制备了结构为ITO/2T-NATA(Xnm)/NPB(25nm)/Alq3:C545T(20nm:质量分数4.5%)/Alq3(30nm)/LiF(1nm)/Al(100nm)的绿光器件,其中X为空穴注入层2T-NATA厚度。分析了2T-NATA的蒸镀厚度分别0,5,10,15,20,25,30,35nm时器件的发光性能。结果表明,2T-NATA的HOMO能级较好的与ITO功函数匹配,降低了空穴注入势垒,引入空穴注入层2T-NATA提高了器件的发光亮度和效率。当2T-NATA厚度为15nm时,器件的效果最好,起亮电压只需2.87V,亮度最高达到18000cd/m2,是不引入空穴注入层亮度的5倍多,在12V时发光效率可达11.4cd/A。     

阴极蒸镀和隔离层对有机发光二极管性能的影响

制备了简单结构的有机发光二极管(OLED)ITO/NPB/Alq3/Al/Ag。实验结果表明,快速蒸镀法制备的Ag阴极越厚,器件性能越差,而慢速蒸镀200nmAg阴极时器件性能也较差。在Alq3与Al阴极之间插入BCP/C60/LiF隔离层后,即使快速蒸镀法制备的Ag厚达280nm,器件的最大电流密度、最大亮度和最大电流效率仍分别高达248.6mA/cm2、5380.7cd/m2和3.52cd/A。隔离层不仅保护NPB和Alq3基本不被玻璃化,还很好地与Alq3和Al阴极匹配,大大提高了器件性能。     

基于混合配体Znq(DBM)的单色和白色OLED

以8-羟基喹啉(q)和1,3-二苯基-1,3-丙二酮定向合成了有机小分子配合物Znq(DBM),将其作为发光层制备了单色有机电致发光器件(OLED)。在结构为ITO/m-MTDATA(5nm)/NPB(40nm)/Znq(DBM)(60nm)/LiF(0.5nm)/Al(100nm)的器件中,启亮电压为5V,最大亮度达到4 575cd/m2。同时又在器件中引入间隔层BCP,研究其不同厚度对OLED性能的影响。在结构为ITO/m-MTDATA(5nm)/NPB(40nm)/BCP(x nm)/Znq(DBM)(60nm)/LiF(0.5nm)/Al(100nm)的器件中,当BCP层厚为0nm时,发光颜色为黄绿色;当BCP层厚为1nm时,发光颜色为白色,色坐标为(0.29,0.33),最大亮度为2 231cd/m2;当BCP层厚为5nm时,发光颜色为蓝色。根据器件结构和性能,讨论了其内部机理。     

Improved efficiency in semiconducting polymer light-emitting diodes

We report visible light emission from metal-polymer diodes made from semiconducting polymers, with indium-tin oxide as the “ohmic” contact, and a variety of metals as the barrier metal. Our results, which confirm the discovery by the Cambridge group [Nature347, 539 (1990)], demonstrate that light-emitting diodes can be fabricated by casting the polymer film on indium-tin oxide from solution with no subsequent polymer processing or heat treatment required. Electrical characterization reveals diode behavior with rectification ratios greater than 10⁵ at sufficiently high voltages. Use of an electrode material with low work function leads to more than an order of magnitude improvement in the room-temperature efficiency of the devices. For example, the most efficient devices made with calcium as the rectifying contact display efficiencies of 0.01 photons per electron.     

Improved efficiency in green polymer light-emitting diodes with air-stable electrodes

By dispersing an electron transporting molecular dopant into the active semiconducting luminescent polymer, we have achieved improved efficiencies for green light-emitting diodes (LEDs). These green emitting LEDs were fabricated by adding an electron transporting molecular dopant, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-l,3,4-oxadiazole (PBD), into the semiconducting luminescent polymer as the emitting layer in the polymer LEDs. The devices used poly(2-cholestanoxy-5-thexyldimethylsilyl-l,4-phenylene vinylene) (CS-PPV), a new soluble green light emitter, as the semiconducting luminescent polymer and either aluminum or indium as the electron injection electrodes. Quantum efficiencies of LEDs with the electron transporting molecular additive in the luminescent polymer and an Al electrode are about 0.3% photons per electron, better by a factor of 18 than similar devices made without the addition of the electron transport molecular dopant; quantum efficiencies of similar LEDs fabricated with an In electrode are 0.23% photons per electron, better by a factor of 16 than devices without the electron transport molecular additive.     

红绿掺杂有机电致发光器件发光性能的研究

制备了结构为ITO/MoO₃(x nm)/NPB(40nm)/CBP:14%GIr1(12.5nm)/CBP:6%R-4b(5nm)/C BP:14% GIr1(12.5nm)/BCP(10nm)/Alq₃( 40nm)/LiF(1nm)/Al(100nm)的红绿磷光器件,G Ir1和R-4B分别为新型绿色和 红色磷光染料,采用绿-红-绿掺杂顺序,结合BCP对空穴的有效限制作用,研究了不同MoO ₃厚度器件的发光 机理。结果表明,在MoO₃为40nm时,器件发光性能较好,在电压 为5V、亮度为100cd·m－2时,得到最大的 电流效率为16.91cd·A－1。为提高器件光效,增加TCTA电子 阻挡层,获得了最高电流效率20.01cd·A－1。原因主要是, TCTA的HOMO能级介于NPB和CBP之间,促进空穴注入;TCTA较高的三线态能量对发光层激子的 限制。     

发光二极管的低频电容特性

通过自建装置精确测试了发光二极管(LED)的低频(小于102Hz)电学特性。电学测量表明,所有LED在低频下都表现出明显的负电容(NC)现象,且频率越低NC现象越明显。调制发光测量表明,相对发光强度在低频下表现出明显饱和现象,并且随频率增加而减小。比较电学和光学的测量结果可以证实,辐射发光是产生NC现象的主要原因。通过对LED电学测量结果的详细分析得出了NC随电压和频率的变化关系式。     

Lifetime improvement of organic light-emitting diodes with a butterfly wing's scale-like nanostructure as a flexible encapsulation layer

Biomimetic nanostructures like butterfly wing's scale were fabricated with an anodic aluminum oxide (AAO) nanoimprint lithography technique. This bio-inspiration nanostructure exhibits an intrinsic hydrophobic property and thus was applied as a flexible encapsulation layer in organic light-emitting diodes (OLEDs) to improve device's lifetime. A ∼80% enhancement on lifetime was obtained with simply imprinting the biomimetic nanostructures onto the flexible substrates. Our work provides a simple encapsulation approach for OLEDs, especially for flexible OLEDs.     

高反射性电流阻挡层用于提高InGaN/GaN发光二极管的光输出功率

由SiO₂/TiO₂分布布拉格反射镜(DBR)和Al镜组成的混合式反射电流阻挡层用于提高InGaN/GaN发光二极管的光输出功率。混合式反射电流阻挡层不仅增强了电流扩展效应而且有效的将射向p金属电极的光子反射防止其对p电极焊点附近光子的吸收。实验结果表明,淀积在p-GaN上1.5个周期的SiO₂/TiO₂DBR和Al镜在455nm垂直入射时的反射率高达97.8%。在20mA的工作电流下,与没有电流阻挡层的发光二极管相比,生长1.5对SiO₂/TiO₂ DBR和Al镜作为电流阻挡层的发光二极管的光输出功率提高了12.5%,且光输出功率的分布更加均匀。     

Reducing the driving voltage of organic light-emitting diodes by inserting a transparent ultrathin layer of oxidized silver as a hole-injecting layer

Organic light-emitting diodes (OLEDs) containing a transparent ultrathin layer of oxidized silver as a hole-injecting layer, placed between a indium–tin-oxide (ITO) electrode and the hole-transporting layer, were fabricated, and their electrical and luminescent properties were investigated. The OLEDs had a structure that consisted of an ITO layer; followed by an ultrathin Ag layer oxidized by a ultraviolet (UV)–ozone surface treatment; a N,N′-di-[(1-naphthyl)-N,N′-diphenyl]-1,1′-biphenyl)-4,4′-diamine (α-NPD) layer; a 5,6,11,12-tetraphenylnaphthacene (rubrene)-doped 9,10-diphenylanthracene (DPA) layer; a tris-(8-hydroxyquinoline) aluminum (Alq₃) layer; a lithium fluoride (LiF) layer; and a Al layer. The operating voltages of the OLEDs with the oxidized Ag (i.e., AgO_x) layer were drastically lower than those of the layer-free OLEDs, because the AgO_x layer, which had high oxidizability, contributed to hole injection as it oxidized the surface of the α-NPD layer. However, the external quantum efficiency of the OLEDs with the AgO_x layer was lower than that of the AgO_x layer-free OLEDs, suggesting that the carrier balance (i.e., the balance between the holes and electrons) became uneven in the emission layer, owing to the insertion of the AgO_x layer. It was assumed that this imbalance resulted from the number of holes in the emission layer being higher because of the increase in hole injection in the AgO_x layer.     

白光有机电致发光器件发光稳定性研究

基于红绿/蓝双发光层,制作了结构为ITO/MoO ₃(10nm)/NPB(40nm)/TCTA(10nm)/CBP:R-4B(2%):GIR1(14%,X nm)/mCP:Firpic(8%,Y nm/BCP(10nm)/Alq₃(40nm)/LiF(1nm)/Al( 100nm)的白色全磷光有机电致发光器件(OLED),通过 调节红绿发光层的厚度X与蓝光发光层的厚度Y,研究了不同发光层厚度器件发 光性能的影响。研究发现:当X 为23nm、Y为7nm时,器件的光效和色坐标都具有 很高的稳定性,在电压分别为5、 10和15V时,色坐标分别为(0.33,0.37)、(0.33,0. 37)和(0.34,0.38);在电压为 5V时,电流密度为0.674mA,亮度为158.7cd ,最大电流效率为26.87cd/A;利用电子阻 挡材料TCTA和空穴阻挡材料BCP能够显著提高载流子的复合效率。分析认为:发光层顺序 为红绿/蓝时,更有利于蓝光的出射,从而使白光的色坐标更稳定。