고려대학교

초록/요약

During the last few years, alternative manufacturing processes have developed to take the place of photolithography and the vacuum process, which are the largest obstacles in the way of reducing the manufacturing cost. One of the most likely alternatives is ink-jet printing technology, by which the conductive, insulating, or semiconducting patterns can be directly printed onto the substrate in single step. The formation of conductive layers by the ink-jet printing method have been demonstrated with several types of conductive inks such as silver, copper, carbon nanotubes and organic conductive materials. Among these materials, polymer based conductive materials such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are of great interest in the field of organic electronics due to their inherent nature of high optical transparency and electrical conductivity, water solubility, and great mechanical flexibility . To apply PEDOT:PSS thin films as transparent electrodes in the applications of displays, solar cells, and other electronic devices, the electrical and optical properties should match those of conventional transparent conductive oxides (TCOs) such as indium-tin-oxide or indium-zinc-oxide. Therefore, to increase the performance of PEDOT:PSS based thin films, several techniques such as adding binders to increase the adhesive strength, and adding alcohol or sorbitol to increase the electrical conductivity have been intensively studied. In the case of adding additional organic compounds to increase the electrical conductivity, organic compounds such as ethylene glycol (EG), dimethyl sulfoxide (DMSO), 1-methyl-2-pyrrolidinone (NMP) and N,N-dimethylformamide (DMF) have been investigated and the electrical conductivity was enhanced 37 ~ 200 fold. In addition, organic compounds having polarity such as poly(vinylpyrrolidone), and oxidizers, for example, toluene sulfonate, dodecyl benzene sulfonate, and camphor sulfonate have been also been studied. However, overall, most of these techniques produced little improvement in the conductivity, and transmittance was decreased. This oxidization doping method has problems of decreased transmittance due to the increase in the absorption concentration of radical cation or polaron. Recently, PEDOT:PSS made great improvement without deterioration of transmittance by adding polyacohol or using materials which have a high boiling point in contrast with protonic doping. Also, this suggests that an increase in the charge mobility and not in the concentration of free carriers is responsible for this effect that the transmittance is not affected by increase in conductivity. In this paper, we investigated the effects of adding different ratios of glycerol in the PEDOT:PSS solution on the electrical conductivity, optical transmittance and surface roughness of PEDOT:PSS thin films. Also, we investigated SAM treatment effect for surface, and we developed the best condition for ink-jet printing. After all these study, we made transistor using developed materials, and their characteristics were better than ITO S/D transistor, lower than Au S/D transistor. That indicates PEDOT:PSS S/D transistor can be used for devices, and this development is needed for all organic display(AOD).