Truly Wearable
It is expected that an era of truly wearable displays will come earlier as Korean researchers developed organic light emitting diodes (OLEDs) that can be worn like clothes.
A joint research team between a KAIST team led by professor Chi Kyung-chul and Kolon Glotech announced on November 22 that they developed OLED technology that can realize OLEDs on a textile substrate.
OLEDs are self-luminous displays that emit light on their own, and are in spotlight as future flexible, foldable and wearable displays. The thinner boards are, the more flexible displays based on the plastic boards are. But they have a problem that they are easily torn and have weak durability.
On the other hand, several-micrometer-thick fibers are thick, but as they were woven with weft yarns and wrap threads, so they are very flexible and durable.
However, as fabrics have a rough surface and large volume expansion (thermal expansion coefficient) due to a temperature rise, which has a limitation in the formation of OLED devices which must undergo a thermal deposition process.
The research team solved this problem by means of a planarization process. They realized a flat type fabric like a glass board without losing the flexible nature of fabrics. Planarized fabrics are more flexible than plastic substrates of the same thickness.
The team succeeded in forming an OLED through a vacuum thermal deposition process on a fabric made in this way. “Multi-layer thin film encapsulation technology” was used to prevent moisture and oxygen from penetrating into OLEDs. It was found that a fabric OLED developed in this way has a life of over 1000 hours and an idle life of more than 3500 hours.
“Textile OLEDs which are more flexible than plastic and has high device reliability are expected to contribute to the development of comfortable wearable displays," professor Choi Kyung-chul said.
The results of the study were published as a cover paper in the November 16 edition of the Advanced Electronic Materials, an international academic journal in the nanoelectronics technology sector.