OLED ink jet printing: introduction and market status

OLED (Organic Light Emitting Diodes) is a flat light emitting technology, made by placing a series of organic thin films (usually carbon based) between two conductors. When an electrical current is applied, light is emitted. OLEDs are used to make displays and lighting panels. OLEDs today are widely used in TVs, smartphones, tablets, laptops and wearables.

While OLED displays excel in color-contrast and efficiency compared to LCDs, they’ve also proven relatively hard to produce on a large scale. Current evaporation-based production techniques involve a lot of wasted material and risk of defects. OLEDs are also extremely sensitive to moisture and oxygen and therefore must be protected with a high performance encapsulating layer.

OLED ink-jet printing

Current OLED producing methods rely on evaporation processes, in which the organic materials are deposited onto a glass sheet through a thin metal stencil, also known as a "shadow mask. This process is problematic, as a significant amount of the material is wasted because it disperses all over the mask, in addition to inherent mask changes which expose the sheet to dust and compromise yields (OLEDs are by nature sensitive to contamination).

Inkjet OLED printing has the desirable ability to allow precision deposits without the use of a mask. It also produces less stray particles, thus boosting yields. These significant advantages make this technology interesting to many companies and virtually all OLED makers have active ink-jet printing development projects.

For many years, companies all over the world invested heavily in inkjet printing processes for OLED displays, but the process is not yet common, as printing OLED displays is a relatively challenging task, and soluble OLED materials are less effective than evaporable ones. Ink-Jet printing is also not able to reach the same high densities of evaporation OLED production, which limits its applications for large-area production (TV panels) and not small mobile, VR and wearable OLEDs.

Printed OLED panels on the market

One area in which inkjet printing is common in the OLED production process is the encapsulation layer deposition. Almost all OLEDs that adopt TFE encapsulation use inkjet printing to deposit the organic elements.

LG UltraFine OLED Pro photo

LG 32EP950 OLED monitor (31" 4K printed OLED panel by JOLED)

For actual OLED emitter layers deposition, currently the only company that commercially uses ink-jet printing is Japan's JOLED, who in 2021 started printing OLED display panels in its 5.5-Gen production line in Nomi, Ishikawa Prefecture, Japan.