發(fā)布時間：2018-05-06 04:09

  本文選題：有機(jī)電致發(fā)光器件 + 壽命測試　； 參考：《華南理工大學(xué)》2015年博士論文

【摘要】：近年來,有機(jī)電致發(fā)光二極管(OLED)因其優(yōu)異的性能而得到高校及企業(yè)的青睞,并獲得了飛速的發(fā)展。同時,OLED因其能夠?qū)崿F(xiàn)自發(fā)光、低功耗的全彩顯示及固態(tài)照明,更被認(rèn)為是下一代顯示及照明的發(fā)展趨勢。OLED發(fā)展至今,研究者們更多注重的是如何提高OLED的發(fā)光效率,而往往忽略了OLED壽命的重要性。事實(shí)證明,真正限制著OLED實(shí)現(xiàn)商業(yè)化運(yùn)用的主要因素之一是壽命。影響OLED壽命的因素是多方面的、復(fù)雜的,往往不能準(zhǔn)確地把OLED老化歸咎于某一種老化機(jī)制,而是多種老化機(jī)制共同作用的結(jié)果。因此,想大幅度地提高OLED壽命,則必須同時解決多種老化機(jī)制對OLED壽命的影響,而這是非常有難度的。同時,目前針對OLED壽命測試的設(shè)備非常有限,基本被韓國壟斷,而且功能單一、自動化程度低,很難滿足生產(chǎn)過程中大規(guī)模壽命測試的需求,嚴(yán)重限制著OLED產(chǎn)業(yè)化的進(jìn)程。本文首先介紹了我們實(shí)驗(yàn)室自主研發(fā)的512路OLED壽命測試系統(tǒng)。該系統(tǒng)是基于Lab VIEW的開發(fā)環(huán)境進(jìn)行研發(fā)的,軟件可靈活設(shè)計,再加上模塊化的硬件,因此可靈活搭建不同規(guī)模的OLED壽命測試系統(tǒng)。測試系統(tǒng)的多線程并行架構(gòu)和代碼的可重復(fù)利用性實(shí)現(xiàn)了真正意義上的512路OLED壽命的同時測試,并且系統(tǒng)在512路同時運(yùn)行的情況下可連續(xù)穩(wěn)定運(yùn)行5000 h以上,可滿足長時間測試的需求。本測試系統(tǒng)有著高精度和寬泛的測試范圍,器件工作電流0-100 m A,工作電壓0-20 V。該測試系統(tǒng)還提供恒流、恒壓、恒亮度這三種不同的測試模式,可用于對OLED老化機(jī)理的進(jìn)一步分析。一般來說,有機(jī)電致發(fā)光器件的壽命測試和老化機(jī)制研究基本上都是在恒定電流模式下進(jìn)行的。在恒流模式下,OLED的亮度呈現(xiàn)不斷衰減的趨勢,這對于OLED未來運(yùn)用到照明面板以及顯示屏上是十分不利的。對于照明面板,OLED亮度的衰減會影響照明面板的使用壽命和照明效果,同時OLED老化也降低了照明面板的功率效率;對于顯示屏,OLED亮度的衰減會造成屏幕上有殘影,同時也會導(dǎo)致屏幕色彩的變化,嚴(yán)重影響用戶的視覺體驗(yàn)。因此,實(shí)現(xiàn)OLED的恒亮度驅(qū)動是非常有必要的。本文利用自主研發(fā)的512路OLED壽命測試系統(tǒng)對OLED進(jìn)行恒亮度壽命測試,得到了電流密度和電壓隨時間的變化曲線,為未來設(shè)計合適的恒亮度驅(qū)動電路提供了參考。從電流密度隨時間變化的曲線可以看出,OLED的電流密度增長基本上可以分為三個老化階段。為了維持恒定的亮度,OLED的電流密度剛開始的時候是呈現(xiàn)緩慢的線性增長,這里我們定義為第一老化階段,也是時間最長的階段;進(jìn)入第二老化階段以后,電流密度開始呈現(xiàn)指數(shù)上升,時間明顯縮短;進(jìn)入第三階段后,電流密度呈現(xiàn)垂直上升的趨勢,幾分鐘的時間內(nèi)器件就被徹底燒壞。我們定義的恒亮度老化測試的壽命Tth,即OLED第一老化階段的時間,也可以用恒流驅(qū)動下的壽命推算公式Ln×Tth=Const.進(jìn)行很好的擬合,其中,L是亮度,n是加速因子。通過對器件老化前后的電流密度-電壓-亮度特性曲線和PL效率進(jìn)行比較,可以看出OLED老化是界面載流子注入下降以及發(fā)光層本體老化這兩個因素共同作用的結(jié)果。同時,OLED老化的熱效應(yīng)也顯示,在維持恒亮度的過程中,器件消耗的功率的增加造成了OLED的溫度上升,最終導(dǎo)致了器件的徹底失效。文章中還證明了恒亮度驅(qū)動下的老化本質(zhì)也是發(fā)光中心的淬滅。本文還分析了溫度對OLED器件壽命及老化機(jī)理的影響,發(fā)現(xiàn)OLED的老化也可以認(rèn)為是庫侖老化和熱老化共同作用的結(jié)果。通過對恒流、恒壓、恒亮度三種驅(qū)動模式的比較,發(fā)現(xiàn)恒亮度驅(qū)動模式也是一種加速老化過程。但是,恒亮度驅(qū)動不但能夠得到不錯的壽命,還能夠提供給用戶更好的視覺體驗(yàn),非常滿足OLED商業(yè)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.

【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TN383.1

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本文編號：1850712