1,064 nm laser irradiation on PEDOT:PSS
70% of Japanese dependence on ITO materials can be replaced


The displays of various IT devices, such as smartphone touch panels, contain transparent electrodes that allow light to pass through while also conducting electricity well.

Indium tin oxide (ITO) is the most commonly used transparent electrode material in the form of a thin film, but although it has high electrical conductivity, it has the disadvantage of being easily broken when bent or bent.

As demand for flexible displays increases, competition to develop next-generation transparent electrodes that can overcome the shortcomings of fragile ITO electrodes is intensifying.

The Korea Institute of Industrial Technology (KITECH) announced on the 17th that it has developed a process technology that can increase electrical conductivity to the level of ITO electrodes by irradiating a conductive polymer with a laser.

Conductive polymers are plastic materials that conduct electricity well and do not break even when pressure is applied due to the polymer's ability to change shape freely.

On the other hand, it is difficult to develop an eco-friendly process because chemical additives such as organic solvents and surfactants are used to increase the electrical conductivity, which is only 1/1000 of that of ITO, and commercialization has not been possible because the conductivity is also lower than that of ITO.

Dr. Chang-Hoon Yoon's research team at the Biotechnology Nano-Optics Convergence Technology Group said,We discovered a physical phenomenon in which the conductivity of a PEDOT:PSS transparent electrode increases by approximately 1,000 times when irradiated with an infrared laser with a wavelength of 1064 nm, and applied this to the process.

PEDOT:PSS transparent electrode is a polymer thin film in the shape of a ball of threads in which conductive PEDOT is surrounded by PSS (Polystrene Sulfonate) like a wire covering. In order to increase conductivity, the PSS must be melted as much as possible so that the PEDOTs can be connected to each other.

When a 1,064 nm laser is shined on this solution, PEDOT absorbs heat first, causing the temperature to rise. At this time, the surrounding PSS melts like a wire covering, exposing a large amount of PEDOT and increasing the conductivity.

Because it is a post-processing process that utilizes an already commercialized PEDOT:PSS solution and laser equipment with a wavelength of 1,064 nm, it is easy and inexpensive.

Since PEDOT:PSS solution can be procured domestically, it can replace ITO material, which has a 70% dependence on Japan, and thus material independence in the transparent electrode field is also expected.

In addition, when applying a conductive polymer solution to a substrate and irradiating it with a laser, patterning work can be performed simultaneously, so a desired pattern can be engraved on a transparent electrode.

Dr. Yoon Chang-hoon said, “While studying the phenomenon of OLED’s luminosity decreasing when a laser is fired at it,“We discovered that when we irradiated a laser on a conductive polymer, which is a material, the electrical resistance decreased,” he explained.

He continued, “The developed process technology can be widely used not only in flexible displays but also in the production of customized wearable devices and foldable solar panels.”