Optimization of electrohydrodynamic-printed organic electrodes for bottom-contact organic thin film transistors

• Optimization of electrohydrodynamic printing of PEDOT:PSS
• Printed PEDOT:PSS acts as source-drain electrode of the organic thin-film transistors (OTFTs)
• Conductivity of the printed PEDOT:PSS is improved by adding a surfactant and a polar solvent.
• Pentacene OTFTs using printed PEDOT:PSS electrodes show field-effect mobility up to 0.157 cm2/V·s.

In this study, we investigate the optimization of printed (3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) as source/drain electrodes for organic thin film transistors (OTFTs) through electrohydrodynamic (EHD) printing process. The EHD-printed PEDOT:PSS electrodes should fulfill the prerequisites of not only high conductivity but also optimum surface tension for successful jetting. The conductivity of PEDOT:PSS was dramatically enhanced from 0.07 to 352 S/cm by the addition of dimethylsulfoxide (DMSO). To use the DMSO-treated PEDOT:PSS solution in the EHD printing process, its surface tension was optimized by the addition of surfactant (Triton X-100), which was found to enable various jetting modes. In the stable cone-jet mode, the patterning of the modified PEDOT:PSS solution was realized on the surface-functionalized SiO2 substrates; the printed line widths were in the range 384 to 81 μm with a line resistance of 8.3 × 103 Ω/mm. In addition, pentacene-based OTFTs employing the EHD-printed PEDOT:PSS as source and drain electrodes were found to exhibit electrical performances superior to an equivalent vacuum-deposited Au-based device.

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