Design Of Mixed Solvent System With Coffee Ring/corrosion Double Inhibition Effect And Construction Of Inkjet Printing QLED

Quantum dot has excellent photoelectric characteristics such as adjustable band gap,narrow emission peak and high fluorescence yield.The resulting Quantum Dot Light-Emitting Diode(QLED)features high brightness,high efficiency,low turn-on voltage and solution-processed.QLED has attracted wide attention.QLED is a series of multilayer device.The optimization of each functional layer is the foundation of high performance device construction.Inkjet printing has unique advantages in the preparation of large area,patterned film,but there are still many challenges to realize the construction of high efficiency inkjet printing devices.Among them,the coffee ring effect and corrosion of ink solvent composition on the lower functional layer is an important aspect.It is an effective way to improve the performance of inkjet printing QLED devices by adjusting the composition of ink solvent,effectively inhibiting the corrosion of the lower functional layer and the coffee ring effect during the deposition of quantum dot.Based on the above background and ideas,this paper selected alkanes,aromatic hydrocarbons,cyclic alkanes,esters and other solvents as the solvent of inkjet printing ink,studied the corrosion regulation of TFB,PVK,and obtained a low erosion quantum dot ink solvent.On this basis,the ink solvent ratio was further optimized,and the dynamic balance between Marangoni flow and capillary flow was effectively regulated by the surface tension gradient of the mixed solvent.High smoothness quantum dot layer was prepared,which effectively improved the transfer of charge carriers and improved the performance of inkjet printing QLED.The main research contents of this paper are as follows:(1)The influence of alkane,aromatic hydrocarbon,cyclic alkane and ester solvent systems on the hole transport layer was studied.Aromatic hydrocarbon,cyclic alkane and ester solvent systems are not ideal quantum-dot ink systems.After solvent treatment,the absorption intensity of TFB film decreases to a certain extent,by about 90%,70%,20%,which indicates that the above solvents have a strong erosion effect on TFB,changing the film morphology and affecting the carrier transmission inside the device.Moreover,the interface defects of functional layer film will increase and the device performance will be reduced.After alkane system treatment,the absorption intensity of TFB has no obvious change,showing a high orthogonal characteristic,which can minimize the influence of solvent on the hole transport layer.After the treatment of PVK film with aromatic hydrocarbon,naphthene and ester solvent systems,the morphology of the film changes,and the alkane system performs well.The alkane system of binary ink was constructed,and the physicochemical properties of solvent and the ratio of ink were optimized.When the volume ratio of n-tridecane to n-octane was 9:1,the uniform quantum dot film was obtained.By studying the surface energy of the substrate,contact Angle and post-treatment mode of the film,high-quality film are prepared and applied in QLED devices.(2)QLED devices were constructed based on inkjet printing,and the relationship between printing times,solution concentration of quantum dot and film thickness and quality of quantum dot was studied,so as to achieve controllable preparation of different quantum dot layer thicknesses and regulate the performance of QLED devices.The influence of solvent ratio on the device performance was explored.The performance of QLED devices was the best when the volume ratio of n-tridecane to n-octane was 9:1.Current leakage existed in QLED devices with other proportions,and the device efficiency was low.Explore the effect of post-treatment method on device performance.Vacuum treatment can improve film uniformity and remove residual solvent to improve device performance.Based on the previous research of quantum dot ink and device post-processing technology,high performance inkjet printing QLED devices are constructed.The maximum luminance of red,green and blue devices is 139800 cd/m~2,284600 cd/m~2and 6662 cd/m~2,respectively,and the maximum external quantum efficiency is 16.91%,16.75%and 1.72%,respectively.The performance of red and green devices is good,and the inkjet printing blue devices need to be further improved.