Optimization Of Quantum Dots Ink And Their Arrays From Inkjet Printing

In the preparation of inkjet printed quantum dot devices,the stability,printability of ink,and the uniformity,regularity of morphology all greatly affect the performance of the devices.Therefore,this thesis has focused on the optimization of inkjet printed quantum dot ink and films.Firstly,the effect of viscosity on the droplet inkjeting process as well as the volume of droplets was studied by the simulation based on COMSOL software,which was further verified by experiment.The results showed that the greater the viscosity,the smaller the flight speed of the droplets,and the less difficult it is to form satellite droplets because of the viscosity consumption and rayleigh instability.When the viscosity was 1?15 Cp,the volume range of droplets obtained by software fitting simulation was 58.10?37.29 pl,which by experiment was 149.9?92.9 pl.Furthermore,regardless of the simulation or experiment,the negative linear relationships between the volume of droplets and the ink viscosity were obtained by linear fitting.This study can help to simplify the quantitative printing of any type of ink with a lower viscosity.Secondly,multi-component quantum dot ink was prepared.The results showed that Cd Se-QDs,UV glue and polyacrylate all have good dispersion in low-polarity halogenated hydrocarbon solvents.Therefore,they were selected as solvents in the ink preparation.Further,UV glue will decline the stability of ink,while low molecular weight polyacrylate does not affect the ink stability and printability.Therefore,polyacrylate alone can be used as the viscous additive,but when UV glue is used as the additive,the polyacrylate is needed to improve the ink properties.Thirdly,the coffee ring effect was overcome by optimizing the solvent ratio,polymer content and drying temperature to improve the morphology of the films.The results showed that the addition of high boiling point solvent is helpful to delay the outward flow of droplets on the substrate.Adjusting polymer content can change the physical properties of the ink,which is beneficial to induce inward flow and hinder outward flow.In addition,the polymer can ameliorate the smoothness of the films because of the leveling effect.Both of them can significantly improve the morphology of the coffee ring.Moreover,adjusting the drying temperature can optimize the pinning of contact line between droplets and substrate,thus further improving the morphology of coffee ring.Finally,the uniform quantum dot films and red-green pixel arrays were all prepared at the quantum dot concentration of 12 mg/ml.The volume ratio of chlorobenzene/cyclohexyl benzene in ink is 8:2,the mass percentage of polyacrylate is 11wt%,and the drying temperature is 25?.Finally,the spherical net-dots and red net-dot-type light guide plate(LGP)were prepared by UV glue/polymer quantum dot ink.The results showed that the net-dots morphology was improved by optimizing the ink dispersibility and droplets stability.The luminescence intensity of LGP gradually decreased,and the color gamut gradually shifted toward the blue light as net-dots diameter became smaller,which are related to the lower bottom illuminance and the lower QDs excitation rate.However,the QDs luminescence peak did not shift with the ink ratio,which is beneficial to the device color fidelity.Finally,LGP with the best optical characteristics was prepared at the ink viscosity of 15 Cp.Specifically,the net-dots diameter was 506 ?m,the height was 15.7 ?m,the LGP relative luminous intensity was 0.518,and the color coordinates were(0.2897,0.0937).In this thesis,the quantum dot ink for inkjet printing was systematically optimized.The uniform sedimentary quantum dot thin film arrays and quantum dot net-dot-light guide plate were prepared.The results of this study can provide technical support for the preparation and performance optimization of quantum dot devices.