OPEN HOUSE 2022
Basic technology of flexible OLED without Alkali EIL was appealed

May 26-30, OPEN HOUSE 2022 was held in NHK Science & Technology Research Laboratories. It's a real exhibition and online exhibition at first time. As regards display, originally flexible OLEDs were disclosed.

Picture 1. Flexible OLED

With respect to basic technology of flexible OLED, originally reversed structure type flexible OLED "iOLED" using original electron injection layer, which was jointly developed with Nippon Shokubai. It's composed of Al cathode/electron injection layer (HIL)/electron transport layer/emitting layer/hole transport layer/hole injection layer/transparent anode. And also, it's not used an alkali series material as HIL, but used original EI material due to decrease of work function. Concretely, strong organic bases is deposited on Al cathode, and then, phenanthrene derivative is deposited, as a result, non-alkali EIL is formed. For this reason, lifetime of OLED can be enhanced because of suppression of occurrence of dark spot. Furthermore, its work function is reduced to approximate 2.4 eV, as a result, electron are effectively injected from cathode to emitting layer. By the way, work function of EIL can be controlled by moving amount of charge.

As a result, if a plastic film is used as a substrate, practice lifetime is obtained. Its thickness is mere 0.5 �o. As picture 1, it's easy to bend and roll, and also, various flexible displays such as, curtain, screen, cloth, and wearable are obtained.

Picture 3. 51.3-inch variable curvature type display

Picture 2. Tiling type 8K OLED

On the other hand, roll storage type 30-inch 4K, tiling 8K, and 51.3-inch variable curvature type display as pilot-produced panels. Their thickness are mere 0.5 �o. Roll storage type can be stored into the under unit because of R=2cm. 8K tiling display is composed of 30-inch 4K × 4 sheets. In this system, sound occurs from display itself really by setting an electroacoustic reception film on rear side of display.

In 51.3-inch curved monitor using 3 30-inch 4K flexible OLEDs, curvature can be changed by use application, for example, while family see TV broadcast in living room at flat state, on the other hand, in the online TV meeting, display is separated into 3 planes. In short, it's possible to use newly various applications, which are difficult to realize by the conventional displays.