利用ZnCl2原位钝化电子传输层提高量子点发光二极管性能

在量子点发光二极管(QLED)中,电子-空穴注入不平衡和量子点层/电子传输层间界面的荧光猝灭限制着QLED效率的提升。基于此,采用金属卤化物(ZnCl₂)原位处理电子传输层方法来减少氧化锌(ZnO)电子传输层的氧空位,同时有效钝化其表面不饱和键,因此在一定程度上实现抑制量子点/电子传输层界面的荧光猝灭和提高QLED中的电子-空穴注入平衡的目的,最终得到了高亮度、高效率的QLED。原位钝化处理后的ZnO基QLED的最大亮度、峰值电流效率、峰值功率效率和峰值外量子效率(EQE)分别从未处理QLED的176 800 cd/m²、9.86 cd/A、8.38 lm/W和7.42%提高到219 200 cd/m²、15.14 cd/A、12.66 lm/W和11.65%。结果表明,ZnCl₂原位钝化ZnO电子传输层对QLED性能的提升起到重要的作用。     

基于电荷传输层优化的量子点发光二极管

采用溶液法旋涂薄膜、真空蒸镀铝电极,制备了ITO/PEDOT∶PSS/空穴传输材料/量子点/纳米氧化锌(ZnO Nanoparticles)/Al结构的量子点发光二极管(QLED)器件。对比了不同纳米氧化锌分散剂对器件性能的影响。当用乙醇和乙醇胺分散氧化锌时,对量子点层破坏较小,器件的亮度最高达22 940cd/m2,电流效率达28.9cd/A。研究了在聚乙烯咔唑(PVK)中掺杂不同比例4,4′-环己基二[N,N-二(4-甲基苯基)苯胺](TAPC)器件的发光特性。在PVK中掺杂TAPC材料能够促进器件空穴传输以及电子空穴注入平衡,当PVK∶TAPC=3∶1时,器件的空穴传输层形貌较为平整,亮度较高;当PVK∶TAPC=1∶1时,器件的开启电压最低。通过对器件膜层表面形貌以及电学、光学性能的对比,分析了电荷传输层优化对器件特性改善的原因。     

基于化学溶液法制备的氧化锌量子点发光二极管研究

氧化锌（ZnO）量子点是一种宽直接带隙半导体纳米颗粒,具有激子束缚能大、绿色环保、量子效应等优点,引起广泛关注。近期,将通过化学溶液法制备的ZnO量子点应用到发光二极管的研究成为热点。文章综述了近几年ZnO量子点发光二极管研究进展,重点介绍了各种结构的ZnO量子点发光二极管最新研究成果,并对ZnO量子点发光二极管的发展趋势进行了展望。     

旋涂法制备量子点LED功能层材料的研究进展北大核心

综述了采用旋涂法制备的量子点发光二极管（QLED）中各功能层材料的研究进展,对可旋涂制备的多种载流子注入层和传输层材料的特性及应用进行了对比总结。多项研究表明：对于电子传输层（ETL）,ZnO和TiO2等无机金属氧化物材料在电子迁移率及器件可靠性方面都要优于有机材料;对于空穴传输层（HTL）,则是具有较高空穴迁移率及成膜质量好的聚[双（4-苯基）（4-丁基苯基）胺]（Poly-TPD）、聚（9-乙烯咔唑）（PVK）等有机聚合物材料应用更为广泛;而MoOx和WOx等无机金属氧化物材料则由于其能级匹配和可靠性方面的优势更多用于空穴注入层。随着技术的成熟及QLED应用中对高效率和高可靠性的要求,无机金属氧化物材料在QLED中的应用将越来越广泛,结合成本低廉的旋涂法,将有力地推动QLED的商业化。     

量子点发光二极管的研究进展北大核心CSCD

量子点材料因其独特的发光特性,在显示和固态照明领域具有极高的应用价值。相比于传统显示器件,量子点发光二极管(QLED)具有高的稳定性、良好溶液可加工性和高色彩饱和度等优势,因而其成为新一代显示技术的核心器件。介绍了QLED的构成、工作机理及研究进展,并指出了其在中国显示行业的应用现状与前景。     

量子点复合物发光二极管发射红外光

以悬浮在半导体聚合物中的量子点为特征的电致发光合成物．可望使应用于通信的高级光源易于发展。多伦多大学发展的一种发光二极管原型能在通信波长产生近红外辐射,其发射强度依据量子点的大小而不同。     

载流子平衡方法提高量子点发光二极管效率的研究

尝试采用三种方式来平衡载流子的浓度,以提高量子点发光二极管(QLED)的外量子效率等性能:在正装结构(ITO/HIL/HTL/QD/ETL/EIL/金属阴极)的QLED的发光层和电子传输层中间插入超薄聚甲基丙烯酸甲脂(PMMA)电子阻挡层;在空穴注入和传输层方面,通过使用更加优化的HIL等来提高空穴注入和传输几率;在QD发光层方面,用短链配体来置换量子点的长链配体以增加载流子向量子点发光层中的传输效率等。在进行量子点配体交换的同时带来了量子点在正交溶剂中的可溶性优势,有利于QLED器件的全溶液法制备。     

面向显示应用的量子点发光器件研究进展

胶体量子点是一种半径接近于激子玻尔半径的新型优质光电材料,其特殊的尺寸效应使其能通过调整尺寸大小实现高纯度的三原色发光、连续可调的光谱以及宽色域.量子点特殊的核壳结构保证了其良好的光/热稳定性;同时,量子点还具有优异的可溶液处理特性,是显示领域研究的热门材料.基于量子点构筑的量子点发光二极管器件也一直被看作是有望取代有...     

无镉无铅环保型蓝光量子点及其发光二极管器件

量子点及其发光二极管器件在显示领域展现出极大的潜力.然而,研究较为成熟的镉系量子点和钙钛矿纳米晶由于含有镉和铅等元素,对环境和人类健康有着较大威胁,限制了其更大规模的应用,无镉无铅量子点及其发光二极管器件显示出更大的潜力.目前,红光和绿光的研究进展较快,而蓝光的报道较少,器件性能也明显落后.本文总结了以磷化铟(InP)...     

量子点发光显示器件

量子点发光二极管（QD—LEDs）是将有机小分子OLED与可发光无机量子点（QD）结合起来而形成的一种新技术。量子点LED既具有聚合物的可溶性，容易制造的优点。同时还具有潜在的类似于磷光材料的高发光效率。     

Solution-processed quantum dot light-emitting diodes based on NiO nanocrystals hole injection layer

Nickel oxide (NiO), as a kind of p-type transition metal oxide (TMO) has shown promising applications in photoelectric devices. In our work, the NiO nanocrystals (NCs) are fabricated by a simple solvothermal method using tert-butyl alcohol and nickel acetylacetonate as precursors at 200 °C for different reaction times. The diameters and valence band edge of the prepared NiO NCs are increased with the increase reaction time from 12 h, 24 h–36 h. The band gaps of the NiO NCs were decreased with the increase time. Selected area electron diffraction (SAED) shows that the NiO NCs is polycrystalline structure. X-ray diffraction (XRD) indicates that the NiO NCs is cubic crystal form. X-ray photoelectron spectroscopy (XPS) shows that the as-prepared NiO NCs have a core of NiO and some form of Ni₂O₃ and NiOOH states on its surface. Further, the obtained NiO NCs is applied on quantum dot light-emitting diode (QLED) as hole injection layer (HILs), showing excellent hole injection properties. Particularly, the NiO NCs for 24 h obtains the best results due to its high band gap and pure cubic crystal phase. Highly bright orange-red QLED with peak luminance up to ∼25580 cd m⁻², and current efficiency (CE) of 5.38 cd A⁻¹ are achieved successfully based on the high performance NiO HIL, further, the device obtained relative long operational lifetime of 11491 h, which has been improved by more than 6- fold as compared to 1839 h for the device based on PEDOT.     

Bright green organic light-emitting devices having a composite electron transport layer

A bright green organic light-emitting device employing a co-deposited Al-Alq₃ layer has been fabricated. The device structure is glass/indium tin oxide (ITO)/ N, N′-diphenyl-N, N′- (3-methylphenyl)-1, 1′-biphenyl-4, 4′-diamine (TPD)/tris(8-quinolinolato) aluminum (Alq₃)/ Al-Alq₃/Al. In this device, Al-Alq₃ is used as electron transport layer (ETL). The device shows an operation voltage of 6.1 V at 20 mA/cm². At optimal condition, the brightness of a device at 20 mA/cm² is 2195 cd/m² achieved a luminance efficiency of 5.64lm/W. The result proves that the composite Al-Alq₃ layer is suitable for the ETL of organic light-emitting devices (OLEDs).     

Plasma-tolerant structure for organic light-emitting diodes with aluminum cathodes fabricated by DC magnetron sputtering: Using a Li-doped electron transport layer

We fabricate aluminum cathodes that are almost free from plasma damage by DC magnetron sputtering for organic light-emitting diodes (OLEDs). While sputtering is widely known to have numerous advantages over conventional evaporation for mass production of devices, it can cause serious damage to organic layers. In this report, we fabricate devices that are free from plasma damage by introducing a 1%-Li-doped electron transport layer (ETL). The difference of external electroluminescence quantum efficiency between OLEDs with the structure ITO/α-NPD/ETL/Al (where ITO is indium tin oxide and α-NPD is N,N′-di(1-naphthyl)-N,N′-diphenylbenzidine) with Al cathodes deposited by conventional evaporation or sputtering is 0.1%, and their driving voltage is identical. We find that the Li-doped ETL should be thicker than 40 nm. Analysis of the depth profile of the ETL by time-of-flight secondary ion mass spectrometry indicates that considerable damage from sputtering extended to a depth of approximately 30 nm, suggesting that high-energy particles penetrated about 30 nm into the ETL.     

Highly efficient all-solution processed blue quantum dot light-emitting diodes based on balanced charge injection achieved by double hole transport layers

Solution-processed blue quantum dot light-emitting diodes (QLEDs) suffer from low device efficiency, whereas the balance of electron and hole injection is critical for obtaining high efficiency. Herein, synergistical double hole transport layers (D-HTLs) are employed, which use poly(9-vinylcarbazole) (PVK) stacked on poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4'-(N-(4-butylphenyl) (TFB). The fabrication of D-HTLs is achieved by using dimethyl formamide (DMF) as the solvent for PVK, with which the underlying TFB layer almost remains unwashed and undamaged during the spin-coating process of PVK layer. TFB/PVK D-HTLs form the stepwise energy level for hole injection, which reduces the hole injection barrier and favors the carrier balance in the emission layer (EML). The optimized blue QLED with TFB/PVK D-HTLs shows a maximum external quantum efficiency (EQE) of 13.7%, which is 3-fold enhancement compared to that of the control device with single TFB HTL. The enhancement of the QLED performance can be attributed to the improvement of surface morphology and charge injection balance for the stepwise D-HTLs based QLEDs. This work manifests the positive effect on performance boost by selecting appropriate solvents towards stepwise D-HTLs formation and paves the way to fabricate highly efficient all-solution processed light emitting diodes.     

多层白色有机发光器件的结构和性能优化

以红、蓝、绿为基,制备了不同发光层组合次序的有机发光器件,研究了各发光层的顺序及厚度对器件性能的影响,并在此基础上构成了白色有机发光器件.通过改变关键发光层的厚度,来调节不同颜色之间的平衡,从而达到色度很好的向色;由于关键发光层的厚度很薄,因此得到的器件在高电压的色度漂移也很小.优化的白光器件在200 mA/cm2时,电流效率为3.78 cd/A,色坐标为x=0.345,y=0.323.根据激子产生和扩散理论,讨论了器件性能对于各发光层的厚度及激子扩散长度的依赖关系,拟合结果与实验结果吻合.     

Highly efficient and stable blue quantum-dot light-emitting diodes based on polyfluorenes with carbazole pendent groups as hole-transporting materials

Highly efficient and stable blue quantum-dot light-emitting diodes (QD-LEDs) have been realized by using poly (9,9-bis(N-(2′-ethylhexyl)-carbazole-3-yl)-2,7-fluorene) (PFCz) as hole-transporting layers (HTLs). Due to the carbazole units as substituents at the 9-position of polyfluorene, PFCz shows higher hole mobility and better electrochemical stability than poly (N-vinlycarbazole) (PVK). As a result, the maximum current efficiency (CE) and external quantum efficiency (EQE) of the blue QD-LEDs increased from 4.32 cd A⁻¹ to 7.9% for PVK HTL to 7.38 cd A⁻¹ and 12.61% for PFCz HTL, respectively. Furthermore, the PFCz-based blue QD-LED exhibited lower turn-on voltage and longer device lifetime than the PVK-based device. The improvement performance of blue QD-LED should be attributed to the conjugated fluorene backbone and the substituents of the carbazole active sites, thus enhancing hole mobility and electrochemical stability. This result demonstrates that polyfluorenes with pendent carbazole groups is a promising hole-transporting materials for improving performance of blue QD-LEDs.     

具有复合空穴传输层的高效低压有机电致发光器件

报道了用m-MTDATA掺杂NPB作复合空穴传输层(c-HTL)的高效率、低电压有机电致发光器件(OLED),器件的最高发光效率达到了5.3cd/A,比NPB作HTL的器件(3.4cd/A)提高了约50%.这是由于c-HTL具有较低的空穴迁移率,改善了发光层中两种载流子的平衡,从而提高了器件性能.进一步在ITO与c-H...     

Properties of non-doped organic light-emitting devices based on an ultrathin iridium complex phosphor layer

Organic light-emitting devices (OLEDs) were constructed with a structure of indium tin oxide (ITO)/N,N'-bis(naphthalen-1-yl)-N'-bis(phenyl)-benzidine (NPB) (50-xnm)/bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2'] iridium (acetylacetonate) [(t-bt)2Ir(acac)] (nm)/NPB (30nm)/Mg:Ag (200nm).A thin blue emission material of NPB was used as a separating layer,and the (t-bt)2Ir(acac) yellow phosphorescent dye was acted as an ultrathin light-emitting layer.TPBI acted as both hole-blocking and electron-transporting layer.By changing the location (x) and the thickness (d) of the phosphor dye,the variation of device performance were investigated.The results showed that all the devices had a turn-on voltage of 2.8V.In the case of d=0.2nm and x=5nm,the OLED had a maximum luminance of 18367cd/m2 and a maximum power efficiency of 5.3lm/W.The high performance is attributed to both direct charge carrier trapping of iridium phosphor dye and the thin NPB separation layer,which effectively confines the recombination zone of charge carriers.     

基于过渡金属氧化物薄膜为连接层的叠层有机电制发光器件的数值模型

By utilizing a two-step process to express the charge generation and separation mechanism of the transition metal oxides （TMOs） interconnector layer, a numerical model was proposed for tandem organic light emitting diodes （OLEDs） with a TMOs thin film as the interconnector layer. This model is valid not only for an n-type TMOs interconnector layer, but also for a p-type TMOs interconnector layer. Based on this model, the influences of different carrier injection barriers at the interface of the electrode/organic layer on the charge generation ability of interconnector layers were studied. In addition, the distribution characteristics of carrier concentration, electric field intensity and potential in the device under different carrier injection barriers were studied. The results show that when keeping one carrier injection barrier as a constant while increasing another carrier injection barrier, carri- ers injected into the device were gradually decreased, the carrier generation ability of the interconnector layer was gradually reduced, the electric field intensity at the interface of the organic/electrode was gradually enhanced, and the electric field distribution became nearly linear： the voltage drops in two light units gradually became the same. Meanwhile, the carrier injection ability decreased as another carrier injection barrier increased. The simulation re- sults agree with the experimental data. The obtained results can provide us with a deep understanding of the work mechanism of TMOs-based tandem OLEDs.