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Enabling the full rainbow of colors in organic light-emitting diode displays

by Jean-François Tremblay
October 31, 2016 | A version of this story appeared in Volume 94, Issue 43

Schematic of an OLED.
Credit: Universal Display/C&EN
At the heart of an organic light-emitting diode is the emissive layer. It contains organic molecules that, when triggered by electrons, emit red, green, or blue light. Kyulux is developing molecules for all three colors, but blue is the biggest challenge.


Launched: March 2015

Headquarters: Fukuoka, Japan

Focus: materials used in organic light-emitting diodes

Technology: energy-efficient molecules employing thermally activated delayed fluorescence

Founders: Chihaya Adachi, Junji Adachi, Akira Minakuchi, and Christopher J. Savoie

Funding or notable partners: $13.5 million from manufacturers including Samsung Display, LG Display, and Japan Display

The futuristic concept of a television or computer monitor that can be rolled up like a piece of paper is coming closer to reality with organic light-emitting diodes, or OLEDs. But display makers still face a major challenge: creating a full rainbow of colors using energy-efficient materials.

OLEDs are already in TVs, but their full potential is not being harnessed. Rather than directly make colors, OLEDs are used to create white light that goes through filters to display colors. True OLED TVs and tomorrow’s flexible displays will only happen after the industry solves the problem of the color blue.

OLEDs create blue and other colors with molecules activated by phosphorescent or fluorescent light. Phosphorescent OLEDs efficiently emit blue but use rare metals, such as iridium, that make the technology impractical for consumer devices. Fluorescent OLEDs, meanwhile, have not delivered on one of OLEDs’ central promises—the efficient conversion of energy into light.

The Japanese start-up Kyulux is trying to achieve both efficiency and affordability with thermally activated delayed fluorescence. Using artificial intelligence methods, the company identifies light-emitting molecules that require less energy to emit colored light. The company selects molecules that don’t contain rare metals, opening the way to low-cost, energy-efficient OLEDs capable of emitting blue.

CEO Christopher J. Savoie says the company’s fluorescent emitters are four times as energy-efficient as current emitters and produce four to five times the light intensity. For consumers, that could soon mean longer-lasting phone batteries or displays bright enough to be viewed in the sunshine.

Savoie is a Japan-based entrepreneur who previously launched Dejima, a start-up that created the basic technology behind the voice-activated phone software Siri. Kyulux’s scientific team also includes Chihaya Adachi, a professor of materials science at Kyushu University who led the team that published an influential paper on using thermally activated delayed fluorescence to emit blue (Nat. Photonics 2014, DOI: 10.1038/nphoton.2014.12).

Kyulux’s technology has yet to address the relatively rapid deterioration of blue-emitting OLEDs. “Blue consumes more energy, so the materials age faster,” Savoie says. The uneven decline of light-emitting materials can cause color imbalances that affect the long-term performance of OLED displays.

But the company’s technology is compatible with the ink-jet manufacturing technologies that are considered critical for making flexible OLED displays. Kateeva and other equipment manufacturers are getting closer to developing an industrial process for ink-jet printing of OLEDs.

For a company created just 18 months ago, Kyulux is progressing by leaps and bounds. In April, it raised $13.5 million from a group of investors including Samsung Display, LG Display, and Japan Display. Potential customers, which Savoie won’t name, are currently evaluating Kyulux emitters. But so far, they are looking at yellow and green materials, rather than the blue ones that could become Kyulux’s main strength. “For blue, we’re a year out,” Savoie says.

As consumers become increasingly aware of the potential of OLEDs, the race is on between Kyulux, Universal Display, and others to discover light-emitting molecules that can generate the full spectrum of colors. Should Kyulux manage to solve the problem of blue, the young company’s technology could become part of every OLED display on the market.

CORRECTION: This story was updated on Nov. 7, 2016, to correctly present Kyulux’s founders.

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