In fact, they have long appeared in our lives, such as smart and interactive transparent refrigerator display

LED transparent landscape screen, which can illuminate at night and be hidden during the day

And 65-inch OLED "wallpaper" display that LG debuted at InfoCm2018

Transparency is a great and cool technology that is not only very practical, but also makes electronic devices more portable. It looks like a kind of magic, and even allows information to be displayed in the air, and it has greater application potential. As long as we make the most of our imagination, we can integrate transparent technology into any item, whether it is a smartphone, a tablet, or a wearable device. In order to realize such a transparent display device, the most important energy storage components are to be transparent, that is to say to have transparent electrodes. And PEDOT:PSS (poly(2,3-dihydrothieno-1,4-dioxin)) is the material most likely to be used in flexible transparent electrodes in the future!

What kind of electrode can be transparent?

Among the light sources visible to the naked eye, electrodes having high light transmittance and high electrical conductivity are transparent electrodes. The quantitative index (Korea Electric Research Institute) is visible light source transmittance of 80% or more at 550 nm, surface impedance of 1000Ω/sq or less, or conductivity of 1000S/m. Generally, the conductive glass with low surface resistance is applied to LCD, OLED, solar battery, etc.; the conductive film with high surface resistance is applied to the touch screen.

What materials are currently used for transparent electrodes?——ITO (Indium Tin Oxide)

ITO is made of indium oxide (In2O3) with a small amount of tin oxide (SnO2). It has excellent conductivity and transmittance, and meets the requirements of transmission signal and transparency. Therefore, most of the transparent electrodes use ITO at this stage. But it has two shortcomings: the shortage of indium resources and the high price, and the other is that ITO is not suitable for flexibility and does not conform to the trend of flexibility.

The future transparent electrode material—PEDOT: PSS (CAS 126213-51-2)

PEDOT is a widely used conductive polymer material, originally developed by the Bayer in German. Because of high conductivity, good stability, large visible light transmittance and other excellent features, it has caught the broad interest of scientists.

Due to the very poor solubility of PEDOT in water, polystyrene sulfonate (PSS) is introduced to improve its solubility. So, PEDOT:PSS has been used in various applications such as a hole transport layer for solar cells, thermoelectric devices, and transparent electrodes. In addition, PEDOT:PSS can be used as a heat shielding film material because of its high optical adsorption in the near infrared region(NIR). The conductive polymer is used for the purpose of improving conductivity. Although there are many kinds of conductive polymers, PEDOT synthesized by using EDOT polymer is regarded as the next generation transparent electrode material because of its high conductivity, good safety, good flexibility, and simple coating process.

In addition, it is also possible to use graphene, silver nanowires and CNT (Carbon Nanotube) for transparent electrodes, and we hope that we can realize the sci-fi movie-like life as soon as possible.