基于蓝光和黄光的白光有机电致发光器件的研究

发布时间：2017-12-28 04:20

本文关键词：基于蓝光和黄光的白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 device,OLED),也称有机电致发光二极管,因基于有机材料,故拥有原材料来源丰富、可制备超薄柔性器件和功能千变万化等特质。近些年,随着学术界与工业界的研究人员的共同攻关,OLED也被冠以高效率、低成本、可大面积生产等特点,并在信息显示产业得到广泛的应用。此外,由于其平面发光的特性,也被制成白光OLED(white OLED,WOLED),用来做固态照明光源或液晶显示器的背光源。利用互补色(蓝+黄)或三基色(红+绿+蓝)可以实现WOLED。然而,在走向产业化的过程中,OLED仍存在器件效率低、发光亮度低、寿命短、良率低和成本昂贵等问题,所以仍然需要以材料、器件结构和内部机理等方面为突破点开展基础科学研究。本工作主要针对互补色WOLED器件中存在的以上问题,首先选取一种蓝光荧光、两种蓝光磷光和一种蓝光延迟荧光发光材料,制作了四组蓝光OLED器件,获得了最好的蓝光OLED器件的性能。与此同时,从新型主体材料和新型器件结构的角度,优化了黄光OLED器件的性能,并进行了深入的发光机理分析。利用蓝光磷光发光材料和黄光磷光发光材料制备并优化了WOLED器件,研究了单层、双层电子传输层对WOLED器件性能的影响。另外,将一种可以发黄光的热激活延迟荧光(thermally acticated delayed fluorescence,TADF)发光材料应用于一种有机紫外探测与电致发光一体化器件,并创新地引入了激子调控层结构,系统研究了不同激子调控层对该器件的影响,在一定程度上解决了目前有机光电子器件集成度低、生产成本高、性能差的问题。本论文将具体从以下五个方面开展研究:1、研究了基于主客体掺杂发光层结构的蓝光OLED器件性能。选取N,N’-dicarbazolyl-3,5-benzene(mCP)作为发光层主体材料,采用四种不同类型的蓝光发光材料分别制备蓝光OLED器件,其中包括,蓝光荧光发光材料4,4’-bis(2,2’-diphenylyinyl)-1,1’-biphenyl(DPVBi)、蓝光磷光发光材料bis[(4,6-difluorophenyl)-pyridinato-N,C2’](picolinate)iridium(III)(FIrpic)和bis(2,4-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate iridium(III)(FIr6)、蓝光TADF发光材料4,5-di(9H-carbazol-9-yl)phthalonitrile(2CzPN),对这些器件的亮度、发光效率等指标,以及发光机理进行分析。研究发现,基于FIrpic的器件由于可以利用了100%的激子发光,并且能量传递充分,因此该器件整体性能最优,亮度最大值达22680 cd/m2,电流效率最大值为9.72 cd/A,功率效率最大值为5.42 lm/W。2、研究了一种具有三线态-三线态湮灭(triplet-triplet annihilation,TTA)性质的新型电荷转移态材料6-{3,5-bis-[9-(4-t-butylphenyl)-9h-carbazol-3-yl]-phenoxy}-2-(4-t-butylphenyl)-benzo[de]isoquinoline-1,3-dione(czphoni)作为主体材料的黄光荧光、磷光和红光荧光、磷光oled器件的性能及其发光机理。将黄光荧光发光材料、黄光磷光发光材料和红光荧光发光材料、红光磷光发光材料以不同掺杂浓度分别掺入czphoni主体材料中,制备了四组oled器件,分别详细研究这些器件的电致发光性能。我们发现荧光oled器件和磷光oled器件的外量子效率都超过了它们对应的理论值。研究发现,主客体间高效的能量传递和通过tta过程的三线态激子上转换为单线态激子的作用机制,在荧光oled器件和磷光oled器件起到重要作用。同时,磷光器件的发光过程还包含载流子直接俘获形成激子。此外,研究结果还发现最优化的荧光oled器件和磷光oled器件的客体掺杂浓度都较高,经验证,主体材料czphoni分子上连接的叔丁基团起到了提高czphoni热稳定性和抑制客体材料浓度淬灭的效应。3、研究了含有rubrene超薄发光层的异质结结构激基复合物界面和异质结结构非激基复合物界面的性能及发光机理。采用异质结结构激基复合物界面、异质结结构非激基复合物界面,并在这两种界面中间插入超薄黄光荧光发光层rubrene,制备了两类oled器件,并通过优化超薄发光层的厚度,来获得高性能黄光oled器件。由于激基复合物是受体材料与给体材料之间形成的电荷转移态,因此激基复合物有实现tadf过程的能力。研究发现,上述基于激基复合物的oled器件中,能量传递和三线态激子的上转换是主要发光机制;基于非激基复合物的oled器件中,载流子直接俘获形成激子是主要发光机制。基于激基复合物的oled器件得到了18311cd/m2的最大亮度、16.6cd/a的最大电流效率和12.7lm/w的最大功率效率;基于非激基复合物的oled器件得到了11860cd/m2的最大亮度、17.3cd/a的最大电流效率和8.1lm/w的最大功率效率。4、系统研究了由掺杂层结构蓝光和超薄层结构黄光组成的woled器件的发光机理,以及电子传输对woled器件性能的影响。采用mcp和firpic主客体掺杂结构作为蓝光发光层,超薄的(tbt)2ir(acac)作为黄光发光层,改变firpic的掺杂浓度和(tbt)2ir(acac)的厚度,优化了woled器件的效率。研究发现,当firpic的掺杂浓度为9wt.%、(tbt)2ir(acac)的厚度为1nm时,器件的启亮电压为2.6v,最大亮度为70520cd/m2,电流效率及功率效率的峰值分别为33.3cd/a和25.6lm/w,白光色坐标为(0.364,0.417)。选取四种不同的电子传输材料作为woled的电子传输层,讨论了电子迁移率、能级结构、三线态能级对woled器件效率、光谱的影响。研究发现,采用tpbi作为电子传输层的WOLED器件获得了不随外加电压变化而变化的稳定光谱,采用4,7-diphenyl-1,10-phenanthroline(Bphen)的WOLED器件获得了最高的效率。随后,引入双层结构电子传输层,即TPBi/Bphen,作为WOLED的电子传输结构,通过改变TPBi和Bphen的厚度,研究了电子传输的控制对WOLED器件的光谱稳定性的影响。当TPBi的厚度为20 nm、Bphen的厚度为20 nm时,WOLED有最好的光谱稳定性,外加电压从7 V变化到11 V时,色坐标漂移仅为(-0.003,0.007)。5、研究了将TADF发光材料应用于一种有机紫外探测与电致发光一体化器件。利用了TADF材料作为光活性层,并创新地引入了激子调控层结构,制备了一体化器件,并系统研究了不同激子调控层对该器件的影响。研究发现,激子调控层的能级对一体化器件的载流子传输过程有很大的影响。另外,研究也对一体化器件在正向偏压和反向偏压下的工作机制进行了分析。结果表明,在350 nm紫外光照射、-1 V偏压下,一体化器件的紫外光探测率高达1.4×1012琼斯;同时,在正向偏压下,该一体化器件可以实现黄光电致发光,具有26370 cd/m2的亮度峰值、8.2 cd/A的电流效率峰值。综上所述,本研究工作为实现基于蓝光和黄光的高性能互补色WOLED器件奠定了实验与理论基础。同时,一体化器件的开发,为未来有机光电子器件的大规模低成本生产打下应用基础,有望在可穿戴设备上得到大规模的应用。
[Abstract]:Organic light-emitting device (OLED), also known as organic light-emitting diodes, is based on organic materials, so it has many characteristics, such as rich raw materials, thin ultrathin flexible devices and ever-changing functions. In recent years, with the joint research of academia and industry researchers, OLED has also been characterized by high efficiency, low cost and large area production, and has been widely applied in information display industry. In addition, the white light OLED (white OLED, WOLED) is also made to be used as a backlight for solid-state lighting or liquid crystal displays due to its plane luminescence. WOLED can be achieved by using complementary color (blue + yellow) or three basic color (red + Green + blue). However, in the process of industrialization, OLED still has some problems such as low device efficiency, low luminance, short life, low yield and high cost. Therefore, we need to carry out basic scientific research as breakthrough point in terms of material, device structure and internal mechanism. Aiming at the above problems in complementary color WOLED devices, we first select a blue light, two blue light phosphors and a blue light delayed luminescent material. We made four sets of blue OLED devices, and got the best blue light OLED devices. At the same time, the performance of the Yellow OLED device was optimized from the angle of new main material and new device structure, and the in-depth analysis of the luminescence mechanism was carried out. Blue and white phosphorescent materials and yellow phosphorescent materials were used to prepare and optimize WOLED devices. The influence of single layer and double layer electron transport layer on the performance of WOLED devices was studied. In addition, a yellow light can be thermally activated delayed fluorescence (thermally acticated delayed fluorescence, TADF) luminescent material is applied to a kind of organic UV detection and electroluminescent devices and integration, innovation and the introduction of the exciton regulation layer structure, studied the influence on the exciton control layer in a certain device. The extent of organic optoelectronic devices with low integration, high production cost, the problems of poor performance. This thesis will be studied in the following five aspects: 1. The performance of the blue light OLED device based on the structure of the host and guest doped luminescent layer is studied. Select N, N '-dicarbazolyl-3,5-benzene (mCP) as the emitting layer main material, the use of four different types of blue luminescent materials were prepared by blue OLED devices, including blue fluorescent materials 4,4' -bis (2,2 '-diphenylyinyl) -1,1' -biphenyl (DPVBi), blue phosphorescent material bis[(4,6-difluorophenyl) -pyridinato-N, C2 "] (picolinate) iridium (III) (FIrpic) and bis (2,4-difluorophenylpyridinato) tetrakis (1-pyrazolyl) borate iridium (III) TADF (FIr6), blue light emitting material 4,5-di (9H-carbazol-9-yl) phthalonitrile (2CzPN), brightness and luminous efficiency of these devices and other indicators, and the luminescence mechanism analysis. It is found that the device based on FIrpic can use 100% exciton emission and full energy transfer, so the device has the best overall performance, the maximum brightness value is 22680 cd/m2, the maximum current efficiency is 9.72 cd/A, and the maximum power efficiency is 5.42 lm/W. 2, study with a three - three triplet triplet annihilation (triplet-triplet annihilation, TTA) model the properties of the charge transfer state material 6-{3,5-bis-[9- (4-t-butylphenyl) -9h-carbazol-3-yl]-phenoxy}-2- (4-t-butylphenyl) -benzo[de]isoquinoline-1,3-dione (czphoni) as the main material properties and luminescence mechanism of yellow light and red fluorescence, phosphorescence fluorescence and phosphorescence of OLED devices. Four groups of OLED devices were prepared by adding yellow light emitting phosphor, yellow light phosphor and red light emitting phosphor and red light phosphor to czphoni material. The electroluminescent properties of these devices were studied in detail. We found that the external quantum efficiency of the fluorescent OLED devices and the phosphorescent OLED devices exceeded their corresponding theoretical values. It is found that efficient energy transfer between host and guest and the action of upconversion of three line exciton through TTA process to single line exciton play an important role in fluorescent OLED devices and phosphorescent OLED devices. At the same time, the luminescence process of the phosphorescent device also includes the direct capture of the carrier to form a exciton. In addition, the results also showed that the target dopant concentration of the optimized fluorescent OLED devices and phosphorescent OLED devices was high. It was verified that the tert butyl group connected with czphoni on the main material played an important role in improving the thermal stability of czphoni and inhibiting the quenching of the concentration of guest materials. 3. The properties and luminescence mechanism of the interface of heterostructure excimer and heterostructure non radical complex with rubrene ultrathin luminescent layer were investigated. The heterojunction structure induced non interface exciplex composite interface, heterojunction structure, and insert the ultra-thin yellow fluorescent light-emitting layer rubrene in the middle of the two interface, two OLED devices were prepared, and by optimizing the ultra-thin light emitting layer thickness, to obtain high performance yellow light OLED device. The radical complex is a charge transfer state between the receptor material and the donor material, so the radical complex has the ability to realize the TADF process. It is found that the energy transfer and upconversion of the three line exciton in the above OLED devices are the main mechanism of luminescence. In the OLED devices based on the excimer, the direct excitation of carriers is the main mechanism of luminescence. OLED device exciplex was obtained based on the maximum power efficiency, the maximum brightness 16.6cd/a 18311cd/m2 the maximum current efficiency of 12.7lm/w and OLED devices; non exciplex was obtained based on the high power efficiency, the maximum brightness 17.3cd/a 11860cd/m2 the maximum current efficiency and 8.1lm/w. 4. The composition of the yellow light and ultrathin layer structure of the doped layer structure is systematically studied.
【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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