By Giana Phelan, Director OLED UX, OLEDWorks
OLED Lighting, It’s Not an OLED display
If you are not carrying an OLED in your pocket already, likely you will be soon. Samsung and LG mobile phones already use OLED screens and the Wall Street Journal recently scooped that Apple will be using OLED displays in all their phones in 2020. What is an OLED display? Millions of tiny carbon-based light emitting pixels that can be individually addressed to provide video and other content. But what if we make just a lone really, really large pixel? This is still a carbon-based light emitting device, but one that can now be used for general and specialty illumination.
OLED Displays give OLED lighting a boost
OLED lighting has benefited from the investment in OLED display, notably with new materials and supply scale. In addition, OLED awareness is gaining traction – who doesn’t know that the iPhone XS has an OLED display? In 2016 LG Display burst into the Superbowl ad game with OLED, with the instantly recognizable voice of Liam Neeson booming the “Future of Television”.
Lighting’s unique performance demands
However, OLED lighting has several performance and cost challenges that are surprisingly different than for display (see chart below). These challenges range from higher brightness levels, 8X – 20X than that of most displays, to longer lifetime requirements (10 years). Guess what? As OLEDs get brighter they typically lose longevity. And yet, this combination of brightness and lifetime must be delivered, and with today’s technology is delivered, for lighting and at a markedly lower cost point than display. Can you imagine spending $110 on a 4” OLED light the way you do for the display on your iPhone X?
Displays operate primarily in video mode with subpixels on the micron range; a missing subpixel due to a short is generally not detected by the human eye.The defect is just too small and obscured by the rapid change in image. In contrast, for OLED lighting, a short will cause a large noticeable dark spot and may ultimately cause the entire light panel, a single large pixel, to fail. Panel designs and manufacturing controls specific to OLED lighting are developed to manage such a failure mode.
OLED Display vs. OLED Lighting
|Passive matrix display||Active matrix display||Lighting|
|Substrate||Glass/ITO pixelated||LTPSilicon TFT||Glass/ITO large area|
|Emission||R,G,B saturated||All, especially white|
|“Pixel” size||~0,005 cm x 0,01cm||12 cm x 12 cm or larger|
|Defect tolerance||Up to 2 pixel||0|
|Value enabler||OLED/Driver IC||TFT backplane||OLED|
|Applications||Sub-display, MP3||Mobile phone display/TV||Any lighting|
|Market development||Declining||Strong growth||Developing|
|Major issue||Limited size||TFT yield/stability||Costs|
You want it white
The reliability demands are not just for hard fails; lighting panels are usually used in clusters and they must accurately match on white color point when installed and as they age. Displays use individual red, green and blue OLED subpixels with each one controlled individually. White OLED lighting has all the colors in one OLED structure. Sounds simple but stacking the color emitters creates unique optical, chemical, semiconductor physics and manufacturing challenges. It’s a balancing act.
Have you ever taken a good look at the lighting in a restaurant, a store, a waiting room or office? Typically, you will see some lights look warm, tending towards amber, and others are almost blue or green tinged. They don’t match! The designer did not intend for that experience. It is the variability in fluorescent or LED light sources. Manufacturing process controls enable OLED white panels top match extremely well creating a homogeneous effect in large installations.
So, thank you to the OLED display industry for all the strides you make in materials, substrates and processing that benefit OLED lighting. And in return we will continue to solve those challenges singular to lighting so light can be experienced as it was meant to be.