Page 72 - Lighting Magazine October 2019

Many people mistakenly believe solid-state lighting (SSL) is just another name for LED, but that’s not quite accurate. There are several other important forms of SSL that lighting professionals need to know more about. BY DAVID SHILLER
The Iris OLED pendant from Neocraft
Although LED has gone mainstream as a light source, it is not the only form of solid-state lighting (SSL) available. There are other types of SSL, each with different inherent advantages and benefits for different specialty lighting applications. Here is a quick look at three other forms of SSL, how they work, as well as their strengths and weaknesses.
OLED
The LEDs that we see every day are technically considered “inorganic light-emitting diodes” or ILEDs. Another form of SSL is “organic light-emitting diodes” or OLEDs, which work by sandwiching different layers (“films”) of organic semiconductors to generate light in very diffuse, larger-area
sources known as “panels.” The electrical voltage applied across the layers of semiconductors cre- ates molecules with extra electrons in one layer, and molecules missing electrons (“holes”) in an adjoining layer. Where these two layers meet (the “junction”), electrons (negatively charged) and holes (net positive charge) combine to release energy in the form of light.
Most LEDs emit light this way, in a single wave- length or color – typically blue – that is used to excite a phosphor coating, creating white light. By contrast, OLEDs can produce very high-quality white light — without “blue pumping” or phos- phors. OLEDs create broad spectrum white light containing much less blue light. This is considered an advantage of OLED, at a time of increasing con- cerns over high blue light content from LEDs, at
70 enLIGHTenment Magazine | october 2019
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