Research On OTFT Based On Ink-jet Printing

In the past decade, organic thin film transistor has become a focus because of broad market prospect and high application potential. As a pattern technology, ink-jet printing gives full play to organic material's characteristic of solution-processable, and this technology has a series of advantages, such as simple technique, low-cost, can depositing high performance organic thin film on the flexible and large area substrate, and so on. So ink-jet printing is considered as one of the most promising industrialized technology. This project is combining ink-jet printing technology with the manufacture of organic thin film transistor, developing a manufacture technology for OTFT, which is simple, low-cost and widespread used.The main work of this thesis is the deposition of organic conducting polymer PEDOT / PSS film utilizing piezoelectric ink-jet printing technology, and then analyzes the impact factors of the conductive performance by comparing with spin-coating, at last completes the characterization of film properties. The main contents include:1) Analyzed the printability of PEDOT/PSS solution. Experimental results show the concentration of PEDOT/PSS solution at 0.16-0.30 wt.% is applicable to Epson inkjet printer.2) Analyzed the relationship between PEDOT/PSS thin film resistance and film length, width and printing times, the results prove that we can deposite uniform film by ink-jet printing, so ink-jet printing technology can be used as a film deposition technology.3) The I-V characteristics indicate that ohmic contact is formed between PEDOT/PSS film and copper electrode, but there is an electric potential drop, which is due to the difference of work function between copper and PEDOT/PSS.4) The physical adsorption of water vapor have a significant effect on the PEDOT / PSS film conductivity;Conductivity-temperature curve shows the conduction mechanism of PEDOT/PSS is hopping conductivity, and the activation energy is 0.096eV.5) Annealing and ethylene glycol doped can significantly improve the conductivity of PEDOT/PSS film. Annealing reduces the surface roughness, then the surface defect density is also reduced, so it effectively improves the conductivity; After ethylene glycol doped, the PEDOT chain turns from the coil conformation of low conductivity into the linear or expanded-coil conformation of high conductivity, so the conductivity increases, but the activation energy reduces. The improving of the roughness after annealing indicates that the annealing temperature about 160℃is more appropriate.The experimental results indicate that ink-jet printing can be used as a film deposition technology as other technology based on solution-processable, which is applied to the field of organic electronic manufacturing.