低温溶液法制备氧化钼及其在QLEDs中的应用

空穴注入层(HIL)在量子点发光二极管(QLEDs)中有重要作用。使用低温溶液法制作了MoOx纳米颗粒,将其在氧化铟锡(ITO)玻璃上旋涂成膜后使用不同温度进行退火处理,并作为空穴注入层进行量子点发光二极管的制作。实验结果表明,氧化钼薄膜有着与ITO玻璃阳极和Poly-TPD空穴传输层匹配的能级,可用作量子点发光二极管的空穴注入层,而使用经100 ℃退火处理后的MoOx薄膜作为空穴注入层的器件性能最佳：器件启亮电压为2.5 V,最高外量子效率为11.6%,在偏压为10 V时,器件的最高亮度达到27 100 cd/m2。     

基于纳米氧化钛电子传输层的量子点发光二极管器件的制备与研究

为了获得高效而经济的光电器件,采用湿法旋涂技术制备量子点发光二极管器件( QLED),并对其光电特性进行了测试。此器件基于纳米二氧化钛( TiO2)的电子传输层,采用ITO玻璃作为阳极,Al为阴极,PEDOT为空穴注入层,TFB为空穴传输层,量子点( QD)作为发光层的结构。研究发现,QLED器件的开启电压为2.6 V,发光高度大于10 cd/m2。实验结果说明了TiO2可以作为获得高效QLED器件以及其他光电器件的一种有效途径。     

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。     

空穴传输层厚度对有机发光二极管性能的影响

采用聚乙烯基咔唑(PVK)作为空穴传输层,8-羟基喹啉铝(Alq3)作为发光层,制备了结构为ITO/PVK/Alq3/Mg∶Ag/Al的有机发光二极管(OLED),通过测试器件的电流-电压-发光亮度特性,研究了空穴传输层厚度对OLED器件性能的影响,优化了器件功能层的厚度匹配.实验结果表明,OLED的光电性能与空穴传输层的厚度密切相关,空穴传输层厚度为15nm时,OLED器件具有最低的启亮电压,最高的发光亮度和最大的发光效率.     

PVK有机薄膜对PF-BT15聚合物发光二极管性能的影响

采用聚乙烯基咔唑(PVK)作为空穴传输层,PF-BT15作为发光层,制备了结构为ITO/PEDOT/PVK(0⁶0 nm)/PF-BT15/Cs2CO3/Al的聚合物发光二极管。通过测试器件的电流密度-电压-发光亮度特性,研究了空穴传输层厚度对聚合物发光二级管器件性能的影响,优化了器件功能层的厚度匹配。实验结构表明,聚合物发光二极管的光电性能与空穴传输层的厚度密切相关,当转速约为2 000 r/s,浓度约为1%,膜厚约为40 nm时,其器件光电性能有较大的提高。     

氩等离子体处理聚合物/量子点表面对量子点发光二极管性能的影响

采用旋转涂布的方法在大气中制备了聚合物/量子点发光复合层,利用氩等离子体处理的方法以去除聚合物/量子点复合层的表面的氧原子等猝灭中心。结果发现,相较于无等离子处理的器件,经过氩等离子处理,量子点发光二极管能够产生具有狭窄发光峰的橙色光,器件的启亮电压为3.5伏,亮度更高,并且电流密度没有明显的衰减现象,器件更加稳定。     

量子点发光器件的制备与仿真分析

为研究量子点发光器件结构与性能的关系,制备了以CdSe/ZnS量子点作为发光层、poly-TPD作为空穴传输层,Alq3作为电子传输层的量子点发光二极管,对器件结构及性能参数进行了表征,结果显示器件具有开启电压低、色纯度高等特点.结合测试数据,对量子点发光二极管进行了器件结构建模,利用隧穿模型及空间电荷限制电流模型对实验结果进行了分析,研究了器件中载流子的注入与传输机理.器件测试与仿真结果表明:各功能层厚度会影响载流子在量子点层的注入平衡,同时器件中载流子的注入与传输存在一转变电压,当外加电压低于转变电压时,器件中载流子的注入主要符合隧穿模型;当外加电压高于转变电压时,器件中载流子的注入主要符合空间电荷限制电流模型.研究结果验证了器件结构建模的合理性,可以利用仿真的方法进行器件结构优化并确定相关参数,这对器件性能的提高具有指导意义.     

Nb2O5空穴注入层的引入对OLEDs性能的影响

在有机发光二极管典型的层状结构中,引入磁控溅射制备Nb2O5超薄膜作空穴注入层,制备了结构为ITO/Nb2O5/TPD/Alq3/A1的器件.Nb2O5层的引入,降低了空穴注入势垒,增强了空穴注入,同时有效阻挡了ITo中ln向有机层的扩散,减少了发光猝灭中心的形成,提高了器件的亮度和效率.研究了不同厚度Nb2 O5层对器件光电性能的影响,发现:当引入Nb2O5层厚度为2 nm时,亮度提高了近2倍,效率由3.5 cd/A增加到了7.8 cd/A,较好地改善了器件的性能,并且性能优于含有CuPc常规注入层的器件.     

基于光刻工艺的高分辨全彩QLED器件制备与性能优化

采用基于光酸反应的光刻工艺,获得均匀的红、绿、蓝三基色量子点薄膜作为发光层,成功制备出高分辨全彩QLED器件(子像素宽度5μm)。通过对光刻量子点表面进行配体钝化,并引入电荷阻挡层以降低非发光区的漏电流,明显提升了全彩QLED的器件性能,所制备器件的最大亮度为23 831 cd/m²,外量子效率为3.78%。     

不同荧光蓝光层厚度的OLED的制备与光电性能

采用蓝色荧光材料1p-TDPVBi结合绿色磷光材料2Ir(ppy)3掺杂到母体材料CBP作为绿光发光层,并且采用3BPhen作为电子传输层和激子阻挡层制备结构为ITO/m-MTDATA(50nm)/NPB(10nm)/p-TDPVBi(dnm)/CBP∶Ir(ppy)38%7nm/BPhen(60nm)/LiF(1nm)/Al的有机发光器件。实验结果表明:通过改变蓝光发光层p-TDPVBi的厚度,得到了高效率的有机发光器件,当p-TDPVBi厚度为5nm时,器件的电流效率和功率效率在4V时达到32.3cd/A和25.3lm/W,亮度在11V时达到31 020cd/m2。研究了p-TDPVBi厚度由3nm变化到9nm,OLED器件的电流密度-电压特性曲线、亮度-电压曲线及电流效率-电压和功率效率-电压等光电性能的变化。     

Light‐Emitting Electrochemical Cells Based on Color‐Tunable Inorganic Colloidal Quantum Dots

Large‐area, ultrathin light‐emitting devices currently inspire architects and interior and automotive designers all over the world. Light‐emitting electrochemical cells (LECs) and quantum dot light‐emitting diodes (QD‐LEDs) belong to the most promising next‐generation device concepts for future flexible and large‐area lighting technologies. Both concepts incorporate solution‐based fabrication techniques, which makes them attractive for low cost applications based on, for example, roll‐to‐roll fabrication or inkjet printing. However, both concepts have unique benefits that justify their appeal. LECs comprise ionic species in the active layer, which leads to the omission of additional organic charge injection and transport layers and reactive cathode materials, thus LECs impress with their simple device architecture. QD‐LEDs impress with purity and opulence of available colors: colloidal quantum dots (QDs) are semiconducting nanocrystals that show high yield light emission, which can be easily tuned over the whole visible spectrum by material composition and size. Emerging technologies that unite the potential of both concepts (LEC and QD‐LED) are covered, either by extending a typical LEC architecture with additional QDs, or by replacing the entire organic LEC emitter with QDs or perovskite nanocrystals, still keeping the easy LEC setup featured by the incorporation of mobile ions.     

Saturated and Multi‐Colored Electroluminescence from Quantum Dots Based Light Emitting Electrochemical Cells

Novel light emitting electrochemical cells (LECs) are fabricated using CdSe‐CdS (core‐shell) quantum dots (QDs) of tuned size and emission blended with polyvinylcarbazole (PVK) and the ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIM‐PF₆). The performances of cells constructed using sequential device layers of indium tin oxide (ITO), poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonate) (PEDOT:PSS), the QD/PVK/IL active layer, and Al are evaluated. Only color saturated electroluminescence from the QDs is observed, without any other emissions from the polymer host or the electrolyte. Blue, green, and red QD‐LECs are prepared. The maximum brightness (≈1000 cd m^‐2) and current efficiency (1.9 cd A^‐1) are comparable to polymer LECs and multilayer QD‐LEDs. White‐light QD‐LECs with Commission Internationale d'Eclairage (CIE) coordinates (0.33, 0.33) are prepared by tuning the mass ratio of R:G:B QDs in the active layer and voltage applied. Transparent QD‐LECs fabricated using transparent silver nanowire (AgNW) composites as the cathode yield an average transmittance greater than 88% over the visible range. Flexible devices are demonstrated by replacing the glass substrates with polyethylene terephthalate (PET).     

Transparent InP Quantum Dot Light‐Emitting Diodes with ZrO2 Electron Transport Layer and Indium Zinc Oxide Top Electrode

Because of outstanding optical properties and non‐vacuum solution processability of colloidal quantum dot (QD) semiconductors, many researchers have developed various light emitting diodes (LEDs) using QD materials. Until now, the Cd‐based QD‐LEDs have shown excellent properties, but the eco‐friendly QD semiconductors have attracted many attentions due to the environmental regulation. And, since there are many issues about the reliability of conventional QD‐LEDs with organic charge transport layers, a stable charge transport layer in various conditions must be developed for this reason. This study proposes the organic/inorganic hybrid QD‐LEDs with Cd‐free InP QDs as light emitting layer and inorganic ZrO₂ nanoparticles as electron transport layer. The QD‐LED with bottom emission structure shows the luminescence of 530 cd m^?2 and the current efficiency of 1 cd/A. To realize the transparent QD‐LED display, the two‐step sputtering process of indium zinc oxide (IZO) top electrode is applied to the devices and this study could fabricate the transparent QD‐LED device with the transmittance of more than 74% for whole device array. And when the IZO top electrode with high work‐function is applied to top transparent anode, the device could maintain the current efficiency within the driving voltage range without well‐known roll‐off phenomenon in QD‐LED devices.     

Green InP/ZnSeS/ZnS Core Multi-Shelled Quantum Dots Synthesized with Aminophosphine for Effective Display Applications

InP quantum dots (QDs) are emerging as promising materials for replacing cadmium-based QDs in view of their heavy metal-free and tunable luminescence. However, the development of InP QD materials still lags due to the expensive and flammable phosphorus precursors, and also the unsatisfactory repeatability caused by the fast nucleation rate. Adopting lowly reactive P precursor aminophosphine can overcome this issue, but their low photoluminescence quantum yield (PLQY) and widening line widths do not apply to the practical application. Through engineering, the core-shell structure of QD, significantly promoted green emissions of QDs were obtained with PLQY of 95% and full width and half maximum (FWHM) of 45 nm, which demonstrated the highest PLQY record obtained from the aminophosphine system. Moreover, due to the residue halogen atoms on the QD surface as inorganic ligands to prevent further oxidization, these InP QDs demonstrated the ultra-long operational lifetime (over 1000 h) for QDs based color enhancement film. By optimizing the device structure, an inverted green InP quantum dot light-emitting diode (QLED) with external quantum efficiency (EQE) of 7.06% was also demonstrated, which showed a significant promise of these InP QDs in highly effective optoelectronic devices.     

Microwave‐Assisted Preparation of White Fluorescent Graphene Quantum Dots as a Novel Phosphor for Enhanced White‐Light‐Emitting Diodes

Graphene quantum dots (GQDs) with white fluorescence are synthesized by a microwave‐assisted hydrothermal method using graphite as the precursor. A solution‐processed white‐light‐emitting diode (WLED) is fabricated using the as‐prepared white fluorescent GQDs (white‐light‐emitting graphene quantum dots, WGQDs) doped 4,4‐bis(carbazol‐9‐yl)biphenyl as the emissive layer. White‐light emission is obtained from the WLED with 10 wt% doping concentration of WGQDs, which shows a luminance of 200 cd m^?2 at the applied voltage of 11–14 V. Importantly, an external quantum efficiency of 0.2% is achieved, which is the highest among all the reported WLED based on GQDs or carbon dots. The results demonstrate that WGQDs as a novel phosphor may open up a new avenue to develop the environmentally friendly WLEDs for practical application in solid‐state lighting.     

InAs/GaAs系列量子点研究

为了获得波长长、均匀性好和发光效率高的量子点,采用分子束外延(MBE)技术和S-K应变自组装模式,在GaAs(100)衬底上研究生长了三种InAs量子点。采用MBE配备的RHEED确定了工艺参数:As压维持在1.33×10-5Pa;InAs量子点和In0.2Ga0.8As的生长温度为500℃;565℃生长50nmGaAs覆盖层。生长了垂直耦合量子点(InAs1.8ML/GaAs5nm/InAs1.8ML)、阱内量子点(In0.2Ga0.8As5nm/InAs2.4ML/In0.2Ga0.8As5nm)和柱状岛量子点(InAs分别生长1.9、1.7、1.5ML,停顿20s后,生长间隔层GaAs2nm)。测得对应的室温光致发光(PL)谱峰值波长分别为1.038、1.201、1.087μm,半峰宽为119.6、128.0、72.2nm、相对发光强度为0.034、0.153、0.29。根据PL谱的峰位、半峰宽和相对发光强与量子点波长、均匀性和发光效率的对应关系,可知量子点波长有不同程度的增加、均匀性越来越好、发光效率显著增强。     

High‐Efficient Deep‐Blue Light‐Emitting Diodes by Using High Quality ZnxCd1‐xS/ZnS Core/Shell Quantum Dots

High‐quality violet‐blue emitting Zn_xCd_1‐xS/ZnS core/shell quantum dots (QDs) are synthesized by a new method, called “nucleation at low temperature/shell growth at high temperature”. The resulting nearly monodisperse Zn_xCd_1‐xS/ZnS core/shell QDs have high PL quantum yield (near to 100%), high color purity (FWHM) <25 nm), good color tunability in the violet‐blue optical window from 400 to 470 nm, and good chemical/photochemical stability. More importantly, the new well‐established protocols are easy to apply to large‐scale synthesis; around 37 g Zn_xCd_1‐xS/ZnS core/shell QDs can be easily synthesized in one batch reaction. Highly efficient deep‐blue quantum dot‐based light‐emitting diodes (QD‐LEDs) are demonstrated by employing the Zn_xCd_1‐xS/ZnS core/shell QDs as emitters. The bright and efficient QD‐LEDs show a maximum luminance up to 4100 cd m^?2, and peak external quantum efficiency (EQE) of 3.8%, corresponding to 1.13 cd A^?1 in luminous efficiency. Such high value of the peak EQE can be comparable with OLED technology. These results signify a remarkable progress, not only in the synthesis of high‐quality QDs but also in QD‐LEDs that offer a practicle platform for the realization of QD‐based violet‐blue display and lighting.     

Efficient Near‐Infrared Light‐Emitting Diodes based on In(Zn)As–In(Zn)P–GaP–ZnS Quantum Dots

Near‐infrared (NIR) lighting plays an increasingly important role in new facial recognition technologies and eye‐tracking devices, where covert and nonvisible illumination is needed. In particular, mobile or wearable gadgets that employ these technologies require electronic lighting components with ultrathin and flexible form factors that are currently unfulfilled by conventional GaAs‐based diodes. Colloidal quantum dots (QDs) and emerging perovskite light‐emitting diodes (LEDs) may fill this gap, but generally employ restricted heavy metals such as cadmium or lead. Here, a new NIR‐emitting diode based on heavy‐metal‐free In(Zn)As–In(Zn)P–GaP–ZnS quantum dots is reported. The quantum dots are prepared with a giant shell structure, enabled by a continuous injection synthesis approach, and display intense photoluminescence at 850 nm with a high quantum efficiency of 75%. A postsynthetic ligand exchange to a shorter‐chain 1‐mercapto‐6‐hexanol (MCH) affords the QDs with processability in polar solvents as well as an enhanced charge‐transport performance in electronic devices. Using solution‐processing methods, an ITO/ZnO/PEIE/QD/Poly‐TPD/MoO₃/Al electroluminescent device is fabricated and a high external quantum efficiency of 4.6% and a maximum radiance of 8.2 W sr^?1 m^?2 are achieved. This represents a significant leap in performance for NIR devices employing a colloidal III–V semiconductor QD system, and may find significant applications in emerging consumer electronic products.     

基于DOPPP的高效白光OLED器件

采用真空热蒸镀的方法,以荧光染料1-(2,5-d imethoxy-4-(1-pyrenyl)-phenyl)pyrene (DOPPP)为蓝发光 层,5,6,11,2-Tetraphenylnaphthacene (Rubrene)为黄发光层,制备了结构为ITO/m-M TDATA(10nm)/NPB(30nm)/ Rubrene (0.2nm)/ DOPPP (x nm)/TAZ(10nm)/Alq₃(30nm)/LiF(0.5nm)/Al的双发光层的高效白色有机电 致发光器件(OLED)。通过调整DOPPP层的厚度,研究器件的发光性能。当DOPPP层厚小 于25nm时,器件以 黄光发射为主;当DOPPP层厚为25nm时器件的性能最佳,在电流密度为209.18mA/cm²时,获得最 大亮度为9232cd/m²,在电流密度为103.712mA/cm²时获得最大电流效率4.68cd/A, 并随着驱动电压 的升高,器件的色坐标从(0.366,0.365)变化到(0.384,0.399),都在白光的范围之内;当DOPPP层厚度超过25nm时,器件的效率和亮度 都开始下降。