基于新型中间连接层的叠层白光有机电致发光器件的研究

发布时间：2018-06-17 23:08

本文选题：OLED + 叠层　；参考：《吉林大学》2015年硕士论文

【摘要】：有机电致发光器件(Organic Light-Emitting Device，简称OLED)，在科技快速发展的今天，一直不断地在进步，尤其在新一代平板显示技术和固态照明两大领域崭露头角，并日趋完善和稳定。叠层白光有机电致发光器件(Tandem WhiteTandem Organic Light-Emitting Device，简称Tandem WOLED)将两个或两个以上单独的有机电致发光单元，依照互补色原则，通过中间连接层串联在一起组成发白光的器件。叠层器件具有亮度高、低功耗、寿命长、色坐标稳定等优点，对未来白光照明有很大的应用前景。叠层OLED的中间连接层(或电荷生成层)不仅具有连接各个发光单元的作用，还负责电荷的生成、传输以及载流子注入到各发光单元。可见，中间连接层对叠层OLED至关重要。因此，中间连接层的设计与优化也成为了对叠层OLED研究工作的重要部分。本论文根据以上思路，基于新型中间连接层的叠层白光有机电致发光器件展开研究，目的是为了设计出新型的中间连接层，不仅能够保证叠层器件的高性能，而且能够使叠层器件的整体结构和中间连接层的结构都得到优化。具体开展了以下工作：首先，采用真空热蒸镀方法制备了单色OLED。制备了三组器件，第一组对不同电子传输层的黄光OLED进行比较，发现电子传输层中含有Bphen的器件表现出明显高的电流密度和更高的效率，得出结论：当金属Ag分别沉积到三种电子传输层Bphen、TmPyPB和TpPyPB上时，Ag会分别扩散到这三种有机材料中，但是Ag只与Bphen发生反应并生产新物质，提高了电子从Ag向Bphen中的注入，降低开启电压，从而提高器件效率，而Ag不会与TmPyPB和TpPyPB发生任何反应。也就是说，对电子传输层Bphen来说Ag才有效。第二组是以Ag为阴极、Bphen为电子传输层的绿光OLED，Bphen的厚度不同，金属Ag与发光层Alq3之间嵌入的Bphen能够明显提高阴极电子的注入，使器件电流密度随电压升高而增大，但是如果Bphen太薄，器件在低电压下会出现负阻效应，只有当Bphen厚度达到5nm时，，负阻效应才会消失。得出结论：金属Ag沉积到电子传输层Bphen的扩散长度约为5nm。第三组以Ag和Mg：Ag分别为阴极的黄光OLED，证明了以Ag为阴极的OLED可与以Mg： Ag合金为阴极的OLED性能媲美，金属Ag作为阴极材料，有效的提高了电子的注入，而且阴极Ag不需要任何修饰层，如LiF、碱金属及其化合物、V2O5等，同时Ag结构简单，易于操作。因此，我们得出结论：Ag是一种很好的阴极材料。接下来，在以Ag为阴极的单色OLED的基础上，设计将金属Ag同时作为阴极和中间连接层应用到Tandem WOLED，同没有Ag作为中间连接层的叠层器件相比，Ag促进了电子注入，明显提高了器件电流密度，说明Ag是一种性能良好的中间连接层材料；再比较不同的电子传输层，对应薄层金属Ag作为中间连接层， Bphen较其它材料有更大的优势；从Tandem WOLED自身结构的特征出发，验证上下发光层的顺序，蓝光发光单元靠近ITO阳极、黄光发光单元靠近阴极Ag，发出的白光性能最稳定；对器件的电子传输层Bphen的厚度加以优化，当厚度增大时，电流密度和亮度变化不大，但是效率有明显提高，使优化后的Tandem具有开启电压低、功率效率低、功率效率高、色坐标稳定、且结构简化的优势，充分利用了金属Ag与有机材料Bphen的特殊性质。最后，基于前面的研究结论，由于Ag的功函数的限制，尽管是以Bphen为电子传输层，其电子注入仍然会受到一定的限制，并且也限制了电子传输层的选择范围，因而我们将常用于OLED阴极的Mg：Ag合金作为叠层器件的内部连接层，研究Mg：Ag合金的比例、及其不同的电子传输层等对叠层WOLED性能的影响。不同浓度比的Mg：Ag与Ag进行比较，因为Mg的功函数较低，掺入功函数较高的Ag，合金同样适合作为叠层器件的中间连接层，甚至有优于Ag的表现；以Mg：Ag为中间连接层的Tandem WOLED，可以在除了Bphen以外的电子传输层中发挥作用，提高器件效率。综上所述，本论文设计并不断优化了Tandem WOLED的中间连接层，将金属Ag和合金Mg：Ag应用为中间连接层，既简化了器件结构，又保证了器件的优良性能，Tandem WOLED表现为低驱动电压、高功率效率和低效率滚降。
[Abstract]:Organic Light - Emitting Device ( OLED ) has been making progress in the rapid development of science and technology , especially in the new generation of flat panel display technology and solid state lighting .

the intermediate connection layer ( or charge generation layer ) of the laminated oled has not only the function of connecting the individual light - emitting units but also the generation , transmission and carrier injection of charge into the light - emitting units .

In order to design a novel middle connecting layer , we can not only guarantee the high performance of the laminated device , but also optimize the whole structure of the laminated device and the structure of the middle connecting layer . The following work is carried out :

The results show that when the metal Ag is deposited on the three electron transport layers Bphen , TmPyPB and TpPyPB , the Ag can diffuse into the three kinds of organic materials , but Ag only reacts with Bphen and produces new substances , which improves the efficiency of the device , and Ag does not react with TmPyPB and TpPyPB . In other words , Ag is only effective for the electron transport layer Bphen .

The second group is the green OLED with Ag as the cathode and Bphen as the electron transport layer . Bphen embedded in the metal Ag and the light - emitting layer Alq3 can obviously improve the electron injection of the cathode , so that the current density of the device increases with the increase of the voltage , but if the Bphen is too thin , the negative resistance effect appears only when the thickness of the Bphen is 5 nm . The conclusion is that the diffusion length of the metal Ag to the electron transport layer Bphen is about 5 nm .

In the third group , Ag and Mg : Ag , respectively , are yellow light OLEDs , which show that the OLED with Ag as cathode is comparable with OLED with Mg : Ag alloy as cathode . As cathode material , Ag can effectively improve electron injection , and Ag does not need any modification layer , such as LiF , alkali metal and its compound , V2O5 , etc . , Ag has simple structure and easy operation . Therefore , it is concluded that Ag is a good cathode material .

Next , on the basis of a single - color OLED using Ag as the cathode , the metal Ag is designed to be applied as a cathode and an intermediate connecting layer to Tandem WOLEDs , and the Ag promotes electron injection compared with a laminated device without Ag as an intermediate connection layer , so that the current density of the device is obviously improved , and the Ag is a middle connecting layer material with good performance ;
Compared with other materials , Bphen has more advantages than other materials by comparing different electron transport layers , and the corresponding thin layer metal Ag is used as the intermediate connecting layer ;
According to the characteristics of the tandem WOLED self structure , the sequence of the upper and lower light emitting layers is verified , the blue light emitting unit is close to the ITO anode , the yellow light emitting unit is close to the cathode Ag , and the white light performance is most stable ;
the thickness of the electron transport layer Bphen of the device is optimized , when the thickness is increased , the current density and the brightness change are not large , but the efficiency is obviously improved , so that the optimized Tandem has the advantages of low opening voltage , low power efficiency , high power efficiency , stable color coordinates and simplified structure , and the special property of the metal Ag and the organic material Bphen is fully utilized .

At last , based on the previous research conclusions , because of the limitation of the work function of Ag , the electron injection is still limited by the Bphen as the electron transport layer , and the choice range of the electron transport layer is also limited . The Mg : Ag alloy used in the cathode of the OLED is used as the internal connection layer of the laminated device .
Tandem WOLEDs with Mg : Ag as the intermediate connection layer can play a role in the electron transport layer other than Bphen , and improve the device efficiency .

In conclusion , the paper designs and continuously optimizes the middle connecting layer of Tandem WOLED , and applies the metal Ag and the alloy Mg : Ag as the intermediate connecting layer , which not only simplifies the structure of the device , but also ensures the excellent performance of the device , and the Tandem WOLED shows low driving voltage , high power efficiency and low efficiency roll - down .
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN383.1

【共引文献】