OLED中电子注入的增强及荧光客体对载流子传输的影响

发布时间：2018-01-13 13:15

本文关键词：OLED中电子注入的增强及荧光客体对载流子传输的影响　出处：《天津理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来,有机电致发光器件(OLED)因其在显示和照明领域所具有的发展潜力,而越来越受到人们的关注。获得低压、高效的OLED是人们所追求的目标。而增强载流子的注入与传输能力是实现这一目标的关键。本论文主要研究了增强OLED器件中电子的注入及器件中荧光客体材料对载流子在发光层中传输的影响。涉及的内容如下:1.我们利用将薄铝层插入碳酸铯注入层的方法来提高OLED中电子的注入能力。为此制备了两组器件。对于以Alq3为发光层和电子传输层的器件,我们将不同厚度的薄铝层插入碳酸铯电子注入层中,当其厚度为0.4nm时,器件获得了6.5 cd/A的最大电流效率。然而当其厚度为0.8 nm时,器件具有最强的电子注入能力。为了验证这种方法的广适性,我们制备了另一组蓝光器件。将0.8 nm的薄铝层插入碳酸铯注入层后,蓝光器件的最大电流效率由4.51 cd/A增大到4.84 cd/A。实验结果证明将合适厚度的薄铝层插入碳酸铯注入层中,可以降低电子注入势垒,增强电子注入,改善器件的性能。这些可以归因于热蒸发的碳酸铯可以分解生成铯的氧化物,铝与铯的氧化物反应生成Al O Cs化合物,Al O Cs化合物可以降低阴极的功函数,通过控制薄铝层的厚度可以控制Al O Cs的数量,进而调节器件的电子注入能力。最后,我们还研究了碳酸铯/Alq3多层重复结构在电子注入及传输方面的可行性,发现其电子注入及传输能力并无明显的提高,且分析了其中的原因。2.通过在电子传输层与Li F/Al阴极之间插入TCNQ电子缓冲层,蓝光OLED的性能得到了改善。经过优化TCNQ的厚度后,我们发现当其厚度为6nm时,器件可以获得最佳的性能。与不含有TCNQ的器件相比,含有6nm的TCNQ的器件的最大亮度、电流效率、功率效率和半寿命分别增加了7.98%、9%、22%、13.6%。器件性能的改善归因于TCNQ电子缓冲层可以促进电子注入能力的增强,提高器件的稳定性。由于TCNQ具有较高的迁移率和稳定性,高的迁移率可以将更多的电子注入到发光层中,使空穴与电子的复合几率增大,从而提高器件的发光效率。同时,高稳定性可以抑制电子传输层的结晶化,使器件更加稳定,且寿命得到延长。3.我们制备了以CBP为主体的蓝色荧光p-i-n同质结OLED。在这些器件中,我们将两种不同的蓝色荧光客体材料掺入主体CBP中,来研究由荧光客体所造成的陷阱中心与散射中心对器件的载流子传输的影响。由实验结果得知在低电压下,低的散射中心能级可以强烈地影响载流子的传输,而深的陷阱中心对载流子的传输影响较小;在高电压下,低的散射中心对载流子的传输影响较小,深的陷阱中心则对载流子的传输影响较大。我们运用了Miller-Abrahams跳跃模型对实验结果进行了解释。最后我们还研究了由荧光客体所造成的陷阱中心和散射中心对器件性能的影响。
[Abstract]:In recent years, organic electroluminescent devices (OLED) have attracted more and more attention and obtained low voltage because of their potential in the field of display and lighting. High efficiency OLED is the goal that people pursue, and enhancing the injection and transmission ability of carriers is the key to achieve this goal. In this thesis, we mainly study the enhancement of electron injection and fluorescence in OLED devices. The effect of guest materials on the transport of carriers in the luminescent layer. The contents are as follows:. 1. We use the method of inserting thin aluminum layer into the caesium carbonate injection layer to improve the electron injection ability in OLED. For the devices with Alq3 as the luminescent layer and electron transport layer, two sets of devices are fabricated. The thin aluminum layer with different thickness is inserted into the caesium carbonate electron implantation layer when the thickness is 0.4 nm. The maximum current efficiency of 6.5 cd/A is obtained. However, when the thickness of the device is 0.8 nm, the device has the strongest electron injection capability. We have prepared another group of blue light devices and inserted 0.8 nm thin aluminum layer into the caesium carbonate implanted layer. The maximum current efficiency of blue light devices is increased from 4.51 cd/A to 4.84 CD / A. the experimental results show that the electron injection barrier can be reduced by inserting a thin aluminum layer of appropriate thickness into the caesium carbonate implanted layer. These can be attributed to the decomposition of cesium oxides by thermal evaporation and the reaction of aluminum with cesium oxides to form Al _ 2O _ 3 compounds. By controlling the thickness of thin aluminum layer, the quantity of Al _ 2O _ 3 Cs can be controlled, and the electron injection ability of the device can be adjusted. We also study the feasibility of cesium carbonate / Alq3 multilayer repeat structure in electron injection and transmission. It is found that the electron injection and transmission capacity of cesium carbonate / Alq3 multilayer repeat structure has not been significantly improved. The reason is analyzed. 2. The TCNQ buffer layer is inserted between the electron transport layer and the Li / Al cathode. The performance of Blu-ray OLED is improved. After optimizing the thickness of TCNQ, we find that when the thickness of TCNQ is 6 nm, the device can get the best performance, compared with the device without TCNQ. The maximum luminance, current efficiency, power efficiency and half-life of the device with 6nm TCNQ are increased by 7.98%, respectively. The improvement of device performance is attributed to the enhancement of electron injection ability and the stability of TCNQ because of the high mobility and stability of TCNQ. At high mobility, more electrons can be injected into the luminescent layer, which increases the recombination probability of holes and electrons, thus improving the luminescence efficiency of the device. At the same time, high stability can inhibit the crystallization of the electron transport layer. We have prepared the blue fluorescence p-i-n homojunction Ole D with CBP as the main body in these devices. Two different blue fluorescent guest materials were mixed into the host CBP. The experimental results show that the low energy level of scattering center can strongly affect the carrier transport at low voltage. The deep trap center has little effect on carrier transmission. At high voltage, the low scattering center has little effect on carrier transmission. The deep trap center has a great influence on the carrier transport. We use the Miller-Abrahams hopping model to explain the experimental results. Finally, we study the effect caused by the fluorescence guest. The effect of trap center and scattering center on the performance of the device.
【学位授予单位】：天津理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN383.1

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