Investigation On The Film Homogeneity Of Ink Jet Printing

In recent years,inkjet printing technology has attracted extensive attention in the field of functional material patterning and the application of optoelectronic devices.Compared with traditional methods such as photolithography,electron beam etching,nanoimprinting,and microcontact printing,ink jet printing has the advantages of simple method,low cost,flexibility and rapidity,and is one of the most promising patterning methods.The "coffee ring" effect is a common phenomenon in the ink jet printing process,which leads to non-uniform deposition of functional materials,reduces the resolution of the print pattern and impairs the performance of the functional device being produced.This article is devoted to a thorough understanding of the mechanism and influencing factors of solution evaporation process through the study of the“coffee ring” effect,and provides a theoretical basis for the preparation of high-performance devices by inkjet printing.The main tasks of this paper are as follows:(1)The fluid mechanism of droplets in the process of evaporation was studied,and a simulation program was designed to study the operation of the droplet’s internal flow field.As a result,it was found that the capillary flow field inside the droplets weakens as the contact angle of the evaporated droplets becomes smaller.(2)The DLVO forces(van der Waals force and electrostatic force between colloidal particles and between colloid and substrate are studied to explain the influence of colloidal solution characteristics on the stability of colloidal solution)evaporation of colloidal solution.The influence of the deposition process.In this paper,a variety of particle materials and solvent materials were used to study the difference in the effect of DLVO force on the colloidal particles under different droplet condition parameters and the different deposition morphologies(eg,coffee ring,uniform film,central Protrusion).(3)Study the morphologies of particle suspension droplets with different solvent components deposited on porous substrates with different pore sizes and film thicknesses.The research on porous substrates and the experimental results can be used to guide the design of flexible printed electronics inks and substrates.(4)To study the preparation of a novel single quantum dot light emitting device.PMMA is added to the traditional structure and the quantum dots are embedded in the insulating PMMA layer.The role of PMMA is to separate the ZnO electron transport layer from the Poly-TPD polymer hole transport layer to prevent backgroundelectroluminescence while providing effective single point electroluminescence.By regulating the temperature of the substrate when the quantum dot solution is dried on the substrate,the result is that the quantum dots are arranged in a ring or a thin film,and the distribution of the quantum dots is controlled.Innovation: The paper proposes a method to use DLVO force to control particles and self-assembled morphology of carbon nanotubes.The paper proposes the relationship between the evaporation time,the penetration time and the particle motion time on the porous substrate and the relationship between the film and the morphology of the porous substrate.The paper added ink-jet printing means in the preparation process of single quantum dot devices to manipulate the assembly of quantum dots.