A group of Korean researchers paved the way for the development of next-generation transparent electrodes that can overcome the shortcomings of indium tin oxide (ITO) electrodes used for flexible displays.
The research team led by Yoon Chang-hoon at the Korea Institute of Industrial Technology announced on Oct. 16 that they succeeded in raising the electrical conductivity of conductive polymers to the level of ITO electrodes by shooting laser on them.
Conductive polymers are a kind of plastic material whose shape can be easily changed.
The new technology, if commercialized, can produce transparent electrodes that can replace imported electrode materials. Korea depends on Japan for 70 percent of electrode materials.
Yoon's team discovered a physical phenomenon where conductivity grows about 1,000 times when an infrared laser of 1,064 nanometer wavelength is applied to a PEDOT: PSS transparent electrode. PEDOT: PSS is a representative kind of conductive polymers.
“While I was studying a phenomenon where luminescence weakens when laser hits an organic light emitting diode (OLED), I found that the electrical resistance of a conductive polymer, which is a material similar to an OLED, fell when it was hit by laser, which was contrary to my expectations,” Yoon said. The conductivity of conductive polymers is about one thousandth of that of ITO, but the team succeeded in increasing the conductivity to the level of existing ITO thin film by applying a conductive polymer solution to a substrate and then shooting laser on it.
This achievement is the world’s first case to realize conductivity at the level of ITO thin film by using a laser-based physical method instead of the existing chemical method. The team’s innovative way makes it easier to realize conductivity at the level of ITO thin film and lowers electrode manufacturing costs as it is a process using an already commercialized PEDOT: PSS solution and equipment that can create a laser at the 1,064 nm wavelength level. Using this way, a company is able to produce transparent electrodes easily and faster as it can create desired patterns on them when applying a conductive polymer solution to a substrate and shooting a laser on them.
“PEDOT: PSS solution can be procured in Korea, so Korea will be able to localize production of transparent electrodes,” Yoon said. “The developed process technology can be used not only for flexible displays, but for production of customized wearable devices and foldable solar panels.”
The results of the study were published in the online edition of Materials Horizons, the world's leading authority in materials published by the Royal Society of Chemistry in the United Kingdom, in September.