| Transparent conductive electrodes(TCEs)have been widely used in many fields,such as touch screens,OLED,thin film solar cells,LCD,transparent display,etc.It is always a challenging issue for the industry and academia to implement the mass production of large-area TCEs at low cost and high throughput.In this thesis,a new method for realizing the large-area and low-cost manufacturing of and high-resolution,high-aspect ratio silver grid transparent electrodes is proposed,which is based on the electric-field–driven fused deposition 3D printing technology and micro-transfer.This thesis systematically analyzes and experimentally validates the proposed process from three aspects: theoretical analysis,process optimization experimental research and specific case study.The process rules of the influence of materials and process parameters on the performance of transparent electrodes were studied,and the manufacturing process windows suitable for high-resolution and high-aspect ratio silver grid electrodes were optimized.The photoelectric properties of the manufactured transparent electrode were verified by specific application cases.The main work of the research is as follows:(1)Based on electric-field–driven fused deposition 3D printing and liquid bridge transfer technology,a new method for mass production of large-area,high-resolution transparent electrodes is proposed.And based on electric-field–driven fused deposition 3D printing and UV-assisted transfer technology,a new method for manufacturing large-area,high-aspect ratio of silver-line transparent electrodes is proposed.The basic principles of the above two methods are summarized and analyzed in combination with existing theories.(2)According to the theoretical analysis results,based on the electric-field–driven fused deposition 3D printing and the liquid bridge transfer technology,a specific experimental study on the manufacture of transparent electrodes was carried out from three aspects: the preparation of nano-silver ink,process parameters and influencing rules,and process window optimization.The experimental results show that:(1)When the temperature of the printing bed is too low,the printing material will not bond strongly with the substrate,which will cause the working mold to fail to replicate.If the temperature is too high,the quality of the printed features will be seriously affected(line width,aspect ratio),which makes liquid bridge transfer difficult to achieve.The ideal printing bed heating temperature range is 30℃~40℃.(2)the nano-silver ink of low surface tension will fill the PDMS mold groove well while partially remaining on the mold surface.While the nano-silver ink with excessive surface tension will be difficult to continuously stay inside the PDMS trench.(3)When the curing temperature is low and the curing time is short,the liquid bridge medium dissolves the silver wire,causing the silver particles to spread laterally;if the temperature is too high and the time is too long,the transferred silver wire may have a fragment missing(the silver wire is discontinuous).It was found that curing at 100℃ for 10 minitues can obtain better quality of micro-transferred silver wire.(3)In order to realize the transfer of silver wire structure with an aspect ratio greater than 0.5,the corresponding experimental research on the proposed UV-assisted transfer technology was carried out.The desired liquid transfer medium(UV ink)was prepared.The research results show that:(1)The influence of the printing bed temperature on the printing master is reflected by the size of the groove opening of the copied PDMS die.If the opening is too large,the filling of the silver paste is incomplete.If the opening is too small,the silver paste transfer success rate will be reduced,and the optimal printing bed heating temperature is about 120℃.(2)When the curing temperature is too low,the degree of curing of the silver paste is too low,resulting in incomplete transfer;when the curing temperature is too high,the degree of curing of the silver paste is too large,which causes the silver wire to become hard and brittle,and is prone to breakage.After testing,the preferred curing conditions are: temperature of 90℃~110℃,curing time of 10 minutes.(3)Different scraper angles result in three filling states: crescent,semi-filled,and fully filled.The angle between the scraper and the scraper direction of the fully filled state required for the study is 80°~90°.(4)The high-temperature heating removes the UV ink cured film.When the temperature is low,the cured film appears to be detached from the substrate,curled,and the like,and the silver wire structure is destroyed.As the heating temperature increases,the silver wire structure tends to become better,and a structurally complete silver wire can be obtained at a temperature of 600℃.(4)A case study of transparent electrodes was carried out by the two methods proposed in this thesis.According to optimized process parameters,high-resolution masters were prepared using electric-field–driven fused deposition 3D printing with PCL as the printing material.The liquid bridge transfer technique was used to realize a grid-structured transparent electrode having an average line width of 4μm(minimum line width of 3μm),a pattern area of 50 mm × 50 mm,a period of 150μm,and a grid structure of 20 mm × 20 mm and a period of 200μm.After testing,the square resistance of the grid electrode is about 12Ω/sq,and the transmittance of the line and grid transparent electrode at 550 nm in the visible light band is 88.94% and 88.15%,respectively.According to the optimized process parameters,PMMA is used as the printing material to prepare the high aspect ratio master.UV-assisted transfer technology is used to realize the transparent electrode with grid structure with an average line width of 15μm,the pattern area of 70mm×70mm,an aspect ratio of about 0.7 and a period of 1000μm.After testing,the square resistance of the wire grid structure electrode is about 0.5Ω/sq,and the light transmittance of different periods(500μm-2000μm)is kept above 94%.The electric heating experiment was carried out by taking a 1000μm periodic wire grid structure as an example,and the results show that the manufactured transparent electrode has very outstanding performance in the field of electric heating. |
PDF Full Text Request