Research On Multilayer Printing Technology Of Flexible Electroluminnescent Device

Flexible organic light-emitting diodes(FOLEDs)are organic light-emitting diodes(OLEDs)that are fabricated based on flexible substrates such as plastics and fabrics,and have the characteristics of being soft,stretchable,and bendable.Therefore,it is especially suitable for sports wearable and body-mounted display devices,and it is also the key research and application target of flexible display technology.At present,the FOLEDs on the market are mainly based on vacuum evaporation,and the FOLEDs prepared by the evaporation process face high material and production costs,the choice of flexible device substrates,and the anti-interference and folding of the prepared devices.Sexuality and many other factors are limited.In this paper,a series of works are mainly carried out to address the above limitations.The main experimental contents and experimental results are as follows:(1)The hole transport layer and the light-emitting layer of the FOLED were prepared by a solution-based inkjet printing process.The inkjet printing process used in the experiments in Chapters 3 and 4 of this paper has the advantages of simple process,high utilization rate of raw materials,digital design,no need for masks,and suitable for large-scale production.It is expected to become the next generation of display device manufacturing technology.For this reason,this paper uses inkjet printing technology to prepare the hole transport layer and the light-emitting layer for the preparation process of FOLEDs,and successfully prepares FOLEDs with two-layer printing,which reduces the cost of device,simplifies the process of device preparation,and conducts technical exploration for low-cost preparation of FOLEDs.(2)Twist resistance is one of the important indicators to mark the performance of FOLEDs.In this paper,traditional indium tin oxide(ITO)was tested by adding polyethylene oxide(PEO)to poly(3,4-ethylenedioxythiophene)poly-(styrenesulfonate)(PEDOT:PSS)as a hole injection layer.The influence of surface modification on the disturbance resistance of FOLEDs was investigated.By comparing the performance of the FOLED with the hole transport layer doped with PEO or not,it is found that the overall performance of the FOLED doped with PEO with a mass ratio of2.5 mg/m L is comparable to that of the FOLED without PEO doping.There is not much difference in the performance of OLEDs,but after the bending disturbance,it can be clearly seen that the brightness of the FOLED without PEO is reduced from 289 cd/m~2 to 120 cd/m~2,while that of the FOLED doped with PEO.The light-emitting device dropped from 443 cd/m~2 to 274 cd/m~2,and the device’s anti-twisting resistance was significantly improved,which provided a new idea for the development of FOLEDs.(3)In the third chapter of this paper,the aluminum-silver alloy is used as the cathode of the FOLED,and the printed semi-transparent FOLED is developed,which further expands the application scene of the FOLED.During the experiments in this paper,it was found that the device prepared by using a single-layer Ag electrode is difficult to light up,and it is very easy to burn out.In order to solve this problem,thin Al was used as a protective layer in this experiment,which effectively prevented the penetration of Ag,and finally an Al/Ag alloy transparent cathode was prepared.On this basis,green and white FOLED were prepared.(4)In addition,considering the application of low-cost flexible substrates,the preliminary research on the printing of optoelectronic functional materials on paper-based flexible substrates with porous structures is also explored in the experiments in Chapter 4.By comparing the film formation of porous structures with those of common substrates,it is found that the porous structure can effectively restrict the flow of ink,thereby avoiding the appearance of the coffee ring phenomenon,which lays a foundation for the development of the preparation technology of flexible paper-based electronic devices.The above experimental results confirm that it is feasible to prepare low-cost FOLEDs through polymer modification,optimized formulation of optoelectronic functional inks,and optimization of inkjet printing process,further improving the performance of multi-layer printing devices and reducing shrinkage.The performance difference between it and traditional vacuum thermal evaporation devices is the focus of future development.