高性能白色磷光有机电致发光器件的研究

发布时间：2018-01-01 08:17

本文关键词：高性能白色磷光有机电致发光器件的研究　出处：《电子科技大学》2016年博士论文　论文类型：学位论文

【摘要】：有机电致发光器件(Organic light-emitting devices,OLEDs)具有体轻质薄、驱动电压低、视角宽、高亮度、高效率、耐高低温等优点,特别的是OLED技术可以实现柔性和透明显示。其中,白光OLED在显示、照明和液晶显示器背光源方面具有潜在的巨大应用,得到了世界范围内科研机构和企业的极大重视,是当前的研究热点之一。在白光OLED器件结构中,有机发光材料是其中一个最重要的成分。然而,有机发光材料容易聚集,导致发光猝灭,从而降低发光效率。为了解决这个问题,通常将发光染料掺杂在主体材料中,组成主客体结构。因为主客体的比例难以控制,采用这种结构使得工艺变得复杂,器件重复性低,良品率低,不利于OLED大面积生产。本论文,采用单层、双层、多层非掺杂超薄层结构的黄色磷光染料bis[2-(4-tertbutylphenyl)benzothiazolato-N,C2’]iridium(acetylacetonate),即(tbt)2Ir(acac)发光层,制备一系列白色OLED器件,简化了器件结构和工艺。从器件的结构设计、性能优化和理论分析方面进行深入研究,获得了高性能白光OLED器件。采用溶液方法制备OLED器件,研究蓝色磷光染料bis[(4,6-difluorophenyl)-pyridinato-N,C2’](picolinate)iridium(III)(FIrpic)光谱波峰变化的影响因素。本论文的主要内容分为以下四个方面:1.采用单层非掺杂超薄层结构(也被称为Delta发光层)的(tbt)2Ir(acac)黄光层,从多方面开展器件优化工作,研究影响WOLED器件性能的主要因素。其一,改变蓝光层掺杂浓度和黄光层厚度。结果表明,当FIrpic掺杂浓度为8%,(tbt)2Ir(acac)厚度为1 nm时,器件性能最好。其二,改变蓝光层主体材料,比较非掺杂黄光层和掺杂黄光层结构,制备了四种白光OLED器件,即N,N’-dicarbazolyl-3,5-benzene(mCP):FIrpic/(tbt)2Ir(acac)和mCP:FIrpic/mCP:(tbt)2Ir(acac),以及(tbt)2Ir(acac)/p-bis(triphenylsilyly)benzene(UGH2):FIrpic和UGH2:(tbt)2Ir(acac)/UGH2:FIrpic。与掺杂结构的器件相比,基于非掺杂黄光层结构的mCP:FIrpic/(tbt)2Ir(acac)和(tbt)2Ir(acac)/UGH2:FIrpic器件,获得了最好的电学性能:最大亮度分别为41790 cd/m2和24700 cd/m2,最大电流效率分别为58.8 cd/A和65.3cd/A,最大外量子效率分别为18.77%和19.04%,以及稳定的白光发光。其三,改变蓝光层和黄光层的相对位置,结果表明结构为(tbt)2Ir(acac)/mCP:FIrpic和UGH2:FIrpic/(tbt)2Ir(acac)的白光OLED器件,主要为蓝色发光。从而说明,由于蓝光层主体材料的载流子传输特性不同,黄光和蓝光发光层的相对位置对器件发光颜色起到重要作用。2.研究了基于双层非掺杂超薄层结构的(tbt)2ir(acac)发光层,结构为4,4’-cyclohexylidenebis[n,n-bis(4-methylphenyl)benzenamine](tapc)/(tbt)2ir(acac)/mcp:firpic/(tbt)2ir(acac)/4,7-diphenyl-1,10-phenanthroline(bphen)的白光oled器件。分析表明,靠近阳极的黄色发光层主要是捕获载流子作用,靠近阴极的黄色发光层贡献黄色发光。通过在阳极加入5nm薄层金作为修饰层,获得了色稳定好的白光器件。其次,采用多个非掺杂超薄层的黄光和蓝光发光层,制备了量子阱结构的白光oled,优化势垒层的材料选择及其厚度来提高器件性能。结果表明,选用6nm的mcp和2,2’,2’’-(1,3,5-benzenetriyl)-tris(1-phenyl-1-h-benzimidazole)(tpbi)作为势垒层,能够获得较为平衡的黄光和蓝光发光强度,实现白光oled器件。基于三层非掺杂超薄层的红绿蓝结构的白光器件表明,非掺杂超薄层对器件内部载流子传输和调控起到重要作用。3.采用载流子传输特性不同的tapc和tpbi作为黄光(tbt)2ir(acac)发光层和蓝光firpic发光层的主体材料,制备双层掺杂结构的白光oled器件。在双发光层之间选择加入不同的间隔层对器件进行优化,并研究了间隔层材料的不同特性对器件性能的影响。当tapc为主体时,与tpbi、tris(2,4,6-trimethyl-3-(pyridin3-yl)phenyl)borane(3tpymb)相比,bphen是最优的间隔层。采用bphen间隔层的器件,获得最大电流效率11.3cd/a和cie坐标(0.394,0.435)的稳定白光。当tpbi为主体时,与间隔层tapc、mcp、tris(4-carbazoyl-9-ylphenyl)amine(tcta)相比,采用4,4’-bis(carbazol-9-yl)biphenyl(cbp)间隔层的器件获得了最大电流效率18.1cd/a,以及cie坐标为(0.284,0.333)的相对稳定白光。分析表明,间隔层的载流子迁移率、三线态能级、能带宽度是对器件性能起到决定性的重要影响因素。分别采用bphen和cbp间隔层,能够促进载流子平衡,扩展激子复合区域,同时还可以改进发光层之间的能量传递作用,从而获得性能优化的白光oled器件。进一步,通过磷光染料敏化方法,研究表明发光层中主体三线态激子在无势垒情况下,会向邻近有机层扩散。通过引入引入激子阻挡层,将激子限制在发光层,能够显著地提高器件效率。4.溶液方法制备了蓝光和白光oled器件,观察到firpic电致发光光谱波峰的变化,并探究原因。溶液加工型蓝光器件中,改变firpic掺杂浓度和发光层溶剂,发现当firpic掺杂浓度高于20%和采用极性较高的溶剂时,firpic光谱中在长波长处的肩峰强度逐渐增强并高于在短波长处的主峰强度。理论分析可知,firpic分子和极性溶剂分子相互作用产生的溶剂化效应,影响了firpic激发态与基态之间的能量差,从而导致firpic光谱中主峰和肩峰的相对强度发生变化。制备了firpic和(tbt)2ir(acac)的溶液加工型白光oled器件,分析电致发光光谱可知,firpic光谱波峰变化与发光层厚度无关,进一步证实了溶剂化效应对FIrpic光谱波峰的作用。同时,溶液方法也获得了光电特性较好的白色发光OLED器件。综上所述,本论文采用非掺杂的单层、双层、多层超薄发光层结构,实现了高性能白光OLED器件。同时,对溶液加工型OLED器件中FIrpic光谱波峰变化的分析,对开发新型高效发光染料及其在溶液加工型OLED中的应用打下了结构和工艺基础。
[Abstract]:Organic electroluminescent devices (Organic, light-emitting devices, OLEDs) with light weight, low driving voltage, wide viewing angle, high brightness, high efficiency, high temperature and other advantages, especially the OLED technology can achieve flexible and transparent display. Among them, the white OLED has great application potential in display, lighting and backlight for liquid crystal display that has been the worldwide attention of research institutions and enterprises, is one of the hot topics. In the white OLED device, organic luminescent material is one of the most important components. However, organic light-emitting materials are easy to gather, resulting in luminescence quenching, thereby reducing the luminous efficiency. In order to solve this problem, usually the luminescent dye doped in the main material, the structure of subject and object. Because the proportion of the subject and the object is difficult to control the structure so that the process becomes complex, low duplication devices, good The rate is low, is not conducive to the production of large area OLED. In this paper, the single, double, multilayer non doped ultra thin structure of the Yellow phosphorescent dye bis[2- (4-tertbutylphenyl) benzothiazolato-N, C2 (acetylacetonate), namely]iridium (TBT) 2Ir (ACAC) light emitting layer, preparing a series of white OLED devices, the device is simplified the structure and process. From the design of the device structure, performance optimization and theoretical analysis of thorough research, to obtain the high performance of white OLED devices. The solution preparation method of OLED device of blue phosphorescent dye bis[(4,6-difluorophenyl) -pyridinato-N, C2 '] (picolinate) Iridium (III) (FIrpic) factors affecting the spectral peak changes the main content of this paper is divided into the following four aspects: 1. the single non doped ultra thin layer structure (also known as the Delta light emitting layer) of the (TBT) 2Ir (ACAC) Huang Guangceng, from many aspects to carry out device optimization work, research The main factors affecting WOLED device performance. First, change the blue and yellow light layer doped layer thickness. The results show that when the concentration of FIrpic is 8% (TBT), 2Ir (ACAC) thickness is 1 nm, the performance is the best. Second, change the material layer blue body, compared with the non doped layer of yellow light the yellow light and the doped layer structure, four kinds of white OLED devices, the preparation of N, N '-dicarbazolyl-3,5-benzene (mCP): FIrpic/ (TBT) 2Ir (ACAC) and mCP:FIrpic/mCP: (TBT) 2Ir (ACAC), and (TBT) 2Ir (ACAC) /p-bis (triphenylsilyly) benzene (UGH2): FIrpic and UGH2: (TBT) 2Ir (ACAC) compared with the device /UGH2:FIrpic. and doping structure, non doped yellow light layer structure based on mCP:FIrpic/ (TBT) 2Ir (ACAC) and (TBT) 2Ir (ACAC) /UGH2:FIrpic device, obtained the best electrical properties: the maximum brightness is 41790 cd/m2 and 24700 cd/m2, the maximum current efficiency respectively. 58.8 cd/A and 65.3cd/A, the most External quantum efficiency were 18.77% and 19.04%, and the stability of the white light. Third, change the relative position of yellow light and blue light layer layer, results show that the structure of (TBT) 2Ir (ACAC) /mCP:FIrpic and UGH2:FIrpic/ (TBT) 2Ir (ACAC) of the white OLED devices, mainly for blue light. Therefore, as the carrier the transmission characteristics of blue layer body of different materials, the luminescence color plays an important role in the study of.2. based on double doped ultra thin structure of the yellow and blue light emitting layer of the relative position of (TBT) 2ir (ACAC) emitting layer structure of 4,4 '-cyclohexylidenebis[n, N-bis (4-methylphenyl) benzenamine] (tapc) / (TBT (2ir) ACAC) /mcp:firpic/ (TBT) 2ir (ACAC) /4,7-diphenyl-1,10-phenanthroline (bphen) of the white OLED devices. The results show that, close to the anode yellow light-emitting layer is the main carrier trapping effect near the cathode yellow light-emitting layer contribution Yellow light. By adding 5nm thin gold as anode modification layer, obtained good color stability of white light devices. Secondly, using a plurality of non doped ultra thin yellow light and blue light emitting layer, white OLED quantum well structure was prepared, improving the performance of the device to optimize the material selection of barrier layer and its thickness. Show that the selection of 6nm MCP and 2,2 ', 2' '- (1,3,5-benzenetriyl) -tris (1-phenyl-1-h-benzimidazole) (tpbi) as a barrier layer to obtain yellow light and blue light intensity is more balanced, the white OLED devices. The three layer structure of red green and blue light emitting devices ultra thin undoped that based on non doped ultra thin layer on the device internal carrier transmission and played an important role in regulation of.3. by the carrier transport characteristics of different tapc and tpbi as the yellow light (TBT) 2ir (ACAC) light emitting material layer and the main body of the blue firpic light emitting layer, double layer preparation White OLED devices doped structure. In the double emitting layer between the spacer layer of different join devices were optimized, and the effects of the different characteristics of interlayer materials on the performance of the device. When the main body is tapc, and tpbi, tris (2,4,6-trimethyl-3- (pyridin3-yl) phenyl) borane (3tpymb), bphen is a spacer the optimal layer. By using the device bphen spacer, the maximum current efficiency of 11.3cd/a and CIE coordinates (0.394,0.435) stable white light. When the tpbi as the main body, tapc, and MCP spacer layer (4-carbazoyl-9-ylphenyl), Tris amine (TCTA) compared with 4,4 '-bis (carbazol-9-yl) biphenyl (CBP) device spacer the maximum current efficiency of 18.1cd/a, and CIE coordinates (0.284,0.333) the relative stability of white light. The analysis shows that the carrier mobility of the spacer, three line state level, band width is an important influence on the performance of the device plays a decisive The influencing factors respectively. Using bphen and CBP interlayer, can promote the balanced carrier, expand exciton recombination region, but also can improve the luminous layer between the energy transfer function, so as to obtain white OLED device performance optimization. Further, the phosphorescent dye sensitization method, research shows that the main light emitting layer three excitons in barrier free under the condition, will spread to nearby the organic layer is introduced. By introducing the exciton blocking layer will limit the exciton in the light emitting layer, can significantly improve the efficiency of the device.4. solution method for blue and white OLED devices were prepared, observed changes of firpic electroluminescent spectrum peaks, and explore the reasons. The solution processing type Blu ray devices. The change of firpic concentration and light emitting layer solvent, when firpic doping concentration is higher than 20% and the high polar solvent, the firpic spectra in the wavelength of the acromion strength and enhanced gradually The main peak strength is higher than that in short wavelength. Theoretical analysis shows that the solvent effect of firpic molecules and polar solvent molecules caused by the interaction of firpic between excited state and ground state energy difference effect, resulting in changes in the relative intensity of the main peak in the firpic spectrum and the acromion. Firpic and preparation of 2ir (ACAC (TBT) the white OLED) solution processing device, analysis of electroluminescence spectra, firpic spectra and luminescence peak changes independent of the thickness, further confirmed the solvent effect of FIrpic spectral peak effect. At the same time, the solution method can obtain a better photoelectric properties of white light emitting device OLED. In summary, this paper uses a single, non doping the double, multilayer light-emitting layer structure, to achieve high performance of white OLED devices. At the same time, analysis of the solution processing device of OLED FIrpic spectral peak change, to develop new and efficient The optical dyes and their applications in the solution processing OLED have laid a foundation for the structure and process.

【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN383.1

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