Manufacturing Method for PEDOT:PSS Electrodes for Organic Thin-Film Transistors

Highly Conductive Organic Thin-Film Transistor Electrodes Based on HAuCl4 Doping and Wettability-Driven Self-Patterning

This technology is a method for manufacturing organic thin-film transistor (OTFT) electrodes by doping a PEDOT:PSS solution with a low concentration of HAuCl4 and drop-casting it onto a selectively hydrophilized substrate to form patterned source/drain electrodes. By creating a wettability contrast through hydrophobic modification and shadow mask UV/ozone treatment, the PEDOT:PSS is configured to self-pattern only on the hydrophilic regions.

While PEDOT:PSS offers excellent transparency, thermal stability, and solution processability, its low electrical conductivity has historically resulted in inferior device performance compared to those using metal-deposited or inorganic electrodes. Previous attempts to enhance conductivity—such as using organic solvents, ionic liquids, or acid treatments—have been limited by a lack of understanding of the enhancement mechanisms and difficulties in efficiently forming patterned electrodes.

This technology uses a small amount of HAuCl4 (10 mM) to induce a conformational rearrangement of PEDOT:PSS chains without forming or aggregating Au nanoparticles, significantly increasing electrical conductivity, work function, and charge mobility. The charge mobility of the 10 mM doped electrode is over seven times higher than that of pure PEDOT:PSS. The simple solution-based doping and self-patterning process allow for electrode formation without vacuum deposition. This technology is applicable to flexible displays, printed circuits, and organic sensor thin-film transistors, enabling the mass production of organic devices with performance comparable to metal electrodes using low-cost solution processes.

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Key Features:

• Forming a dielectric layer on a gate and applying a compound with hydrophobic end groups to modify the surface to be hydrophobic
• Irradiating the hydrophobically modified surface with UV/ozone through a shadow mask to selectively hydrophilize it, thereby obtaining a surface with varying wettability
• Drop-casting the oxidized and doped PEDOT:PSS solution—prepared by adding HAuCl4 to a concentration of 10 mM without causing aggregation, precipitation, or Au nanoparticle formation—onto the hydrophilic regions
• A bottom-contact organic thin-film transistor structure where patterned PEDOT:PSS source/drain electrodes are positioned beneath a P3HT organic semiconductor layer

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This invention was developed with support from the Ministry of Education for the analysis of charge transport mechanisms in π-electron molecular-based n-dimensional nanostructures.

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