有机电致发光器件寿命测试系统研发及老化机理研究

发布时间：2018-05-06 04:09

本文选题：有机电致发光器件 + 寿命测试　；参考：《华南理工大学》2015年博士论文

【摘要】：近年来,有机电致发光二极管(OLED)因其优异的性能而得到高校及企业的青睐,并获得了飞速的发展。同时,OLED因其能够实现自发光、低功耗的全彩显示及固态照明,更被认为是下一代显示及照明的发展趋势。OLED发展至今,研究者们更多注重的是如何提高OLED的发光效率,而往往忽略了OLED寿命的重要性。事实证明,真正限制着OLED实现商业化运用的主要因素之一是寿命。影响OLED寿命的因素是多方面的、复杂的,往往不能准确地把OLED老化归咎于某一种老化机制,而是多种老化机制共同作用的结果。因此,想大幅度地提高OLED寿命,则必须同时解决多种老化机制对OLED寿命的影响,而这是非常有难度的。同时,目前针对OLED寿命测试的设备非常有限,基本被韩国垄断,而且功能单一、自动化程度低,很难满足生产过程中大规模寿命测试的需求,严重限制着OLED产业化的进程。本文首先介绍了我们实验室自主研发的512路OLED寿命测试系统。该系统是基于Lab VIEW的开发环境进行研发的,软件可灵活设计,再加上模块化的硬件,因此可灵活搭建不同规模的OLED寿命测试系统。测试系统的多线程并行架构和代码的可重复利用性实现了真正意义上的512路OLED寿命的同时测试,并且系统在512路同时运行的情况下可连续稳定运行5000 h以上,可满足长时间测试的需求。本测试系统有着高精度和宽泛的测试范围,器件工作电流0-100 m A,工作电压0-20 V。该测试系统还提供恒流、恒压、恒亮度这三种不同的测试模式,可用于对OLED老化机理的进一步分析。一般来说,有机电致发光器件的寿命测试和老化机制研究基本上都是在恒定电流模式下进行的。在恒流模式下,OLED的亮度呈现不断衰减的趋势,这对于OLED未来运用到照明面板以及显示屏上是十分不利的。对于照明面板,OLED亮度的衰减会影响照明面板的使用寿命和照明效果,同时OLED老化也降低了照明面板的功率效率;对于显示屏,OLED亮度的衰减会造成屏幕上有残影,同时也会导致屏幕色彩的变化,严重影响用户的视觉体验。因此,实现OLED的恒亮度驱动是非常有必要的。本文利用自主研发的512路OLED寿命测试系统对OLED进行恒亮度寿命测试,得到了电流密度和电压随时间的变化曲线,为未来设计合适的恒亮度驱动电路提供了参考。从电流密度随时间变化的曲线可以看出,OLED的电流密度增长基本上可以分为三个老化阶段。为了维持恒定的亮度,OLED的电流密度刚开始的时候是呈现缓慢的线性增长,这里我们定义为第一老化阶段,也是时间最长的阶段;进入第二老化阶段以后,电流密度开始呈现指数上升,时间明显缩短;进入第三阶段后,电流密度呈现垂直上升的趋势,几分钟的时间内器件就被彻底烧坏。我们定义的恒亮度老化测试的寿命Tth,即OLED第一老化阶段的时间,也可以用恒流驱动下的寿命推算公式Ln×Tth=Const.进行很好的拟合,其中,L是亮度,n是加速因子。通过对器件老化前后的电流密度-电压-亮度特性曲线和PL效率进行比较,可以看出OLED老化是界面载流子注入下降以及发光层本体老化这两个因素共同作用的结果。同时,OLED老化的热效应也显示,在维持恒亮度的过程中,器件消耗的功率的增加造成了OLED的温度上升,最终导致了器件的彻底失效。文章中还证明了恒亮度驱动下的老化本质也是发光中心的淬灭。本文还分析了温度对OLED器件寿命及老化机理的影响,发现OLED的老化也可以认为是库仑老化和热老化共同作用的结果。通过对恒流、恒压、恒亮度三种驱动模式的比较,发现恒亮度驱动模式也是一种加速老化过程。但是,恒亮度驱动不但能够得到不错的寿命,还能够提供给用户更好的视觉体验,非常满足OLED商业化的需求。
[Abstract]:In recent years, organic electroluminescent diode (OLED) has been favored by universities and enterprises for its excellent performance, and has gained rapid development. At the same time, because of its ability to realize self luminescence, low power full color display and solid-state lighting, OLED has been considered to be the next generation and the development trend of.OLED. The important thing is how to improve the luminescence efficiency of OLED, and often ignore the importance of OLED life. In fact, one of the main factors that really restrict the commercialization of OLED is life. The factors that affect the life of the OLED are multifaceted and complex, it is often inaccurate to attribute the aging of OLED to a certain aging mechanism, but a variety of old ones. As a result of the common effect of the mechanism, it is very difficult to solve the effect of a variety of aging mechanisms on the life of OLED at the same time, and it is very difficult. At the same time, the equipment for OLED life testing is very limited and is basically monopolized by South Korea, and the function is single, and the degree of automation is low, it is difficult to meet the production of OLED. The demand of large scale life testing in the process seriously restricts the process of OLED industrialization. This paper first introduces the 512 way OLED life testing system developed by our laboratory. This system is based on the development environment of Lab VIEW, and the software can be designed flexibly, and then modular hardware is added, so it can be flexible to build a different scale of O LED life test system. The multi thread parallel architecture of the test system and the repeatability of the code have realized the real sense of the simultaneous test of 512 OLED lifespan, and the system can run steadily more than 5000 h in the case of 512 road running simultaneously, which can meet the needs of long time test. This test system has high precision and wide range. The test range, the device working current 0-100 m A, the working voltage 0-20 V., the test system also provides three different testing modes, constant current, constant pressure and constant brightness, which can be used to further analyze the aging mechanism of OLED. Generally speaking, the life testing and aging mechanism of organic electroluminescent devices are basically in constant current mode Under the constant current mode, the brightness of OLED presents a constant attenuation trend, which is very unfavorable to the future application of OLED to the lighting panel and display panel. For the lighting panel, the attenuation of OLED brightness will affect the service life and lighting effect of the lighting panel, while OLED aging also reduces the power efficiency of the lighting panel; On the display screen, the attenuation of OLED brightness will cause the screen to have the residual shadow, and also cause the change of the screen color, which seriously affects the user's visual experience. Therefore, it is necessary to realize the constant brightness driving of the OLED. This paper uses the 512 way OLED life test system independently developed to test the constant luminance life of the OLED, and obtains the current density. The curve of the degree and voltage variation with time provides a reference for the future design of a suitable constant luminance drive circuit. From the curve of the current density with time, the growth of the current density of OLED can be basically divided into three aging stages. In order to maintain constant brightness, the current density of OLED is slow when the current density is just beginning. Linear growth, which we define as the first aging stage, is also the longest period of time; after entering the second aging stage, the current density begins to rise exponentially and the time is obviously shortened; after entering the third stage, the current density presents a vertical upward trend, and the device is completely burnt out in a few minutes. Our definition of constant brightness The life Tth of the aging test, that is, the time of the OLED first aging stage, can also be fitted well with the lifetime calculation formula Ln x Tth=Const. under the constant current drive. Among them, L is the brightness and the n is the acceleration factor. By comparing the current density voltage luminance curve and the PL efficiency before and after the aging of the device, it can be seen that the aging is the OLED aging. At the same time, the heat effect of OLED aging also shows that the increase of the power consumed by the device causes the temperature rise of the OLED in the process of maintaining the constant brightness, which eventually leads to the failure of the bottom of the device. The article also proves that the constant brightness is driven by the OLED. The essence of aging is also the quenching of the luminescence center. This paper also analyzes the effect of temperature on the life and aging mechanism of OLED devices. It is found that the aging of OLED can also be considered as the result of the co action of Coulomb aging and thermal aging. By comparing the three driving modes of constant current, constant pressure and constant brightness, it is found that the mode of constant luminance driving is also a kind of accelerated aging. However, the constant brightness driver can not only get a good life expectancy, but also provide users with better visual experience and meet the needs of OLED commercialization.

【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN383.1

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