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How Light Emitting Diodes (LEDs) Work

LED TVs and the Future of Light Emitting Diodes

LED TVs
LED TVs, showing images of the Greek Islands, line the wall. mbbirdy/Getty Images

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LEDs have come a long way since the early days of lighting up digital clock faces. In the 2000s, LCD TVs took over the high-definition market and represented a huge step over old standard definition CRT televisions. LCD displays were even a major step above HD rear-projection sets that weighed well over 100 pounds (45.4 kilograms). But LED technology changed the market. While LCD TVs were far thinner and lighter than massive rear-projection sets, they still used cold cathode fluorescent tubes to project a white light onto the pixels that make up the screen. Those add weight and thickness to the TV set. LEDs solved both problems.

Have you ever seen a gigantic flat-screen TV barely an inch thick? It was probably an LED television. Here's where the acronyms get a bit confusing: Those LED TVs are still LCD TVs, because the screens themselves are comprised of liquid crystals. Technically, they're LED-backlit LCD TVs. Instead of fluorescent tubes, LEDs shine light from behind the screen, illuminating the pixels to create an image. Due to the small size and low power consumption of LEDs, LED-backlit TVs are far thinner than regular LCD sets and are also more energy efficient. They can also provide a wider color gamut, producing more vivid pictures.

There are several different types of LED-backlit sets are on the market – and not all are created equal. Many sets use white LED edge lighting to shine light across the display. The only real advantage afforded by these sets is thinness. RGB LED-backlit sets, on the other hand, provide improved color. Some configurations even allow for a technique called local dimming, where LEDs in different parts of the display can be brightened or dimmed independently to create a more dynamic picture [source: Morrison]. And that highlights one more great advantage of LEDs over CFLs: Because the LEDs can actually be instantly toggled on and off, they produce awesome black levels in dark scenes. Since the white fluorescent lamps have to remain on during TV use, some light tends to bleed through and lighten the picture in dark scenes.

Some of the newest LED displays are made with organic light emitting diodes, or OLEDs. The organic materials used to create these semiconductors are flexible, allowing scientists to create bendable lights and displays – some manufacturers have already started producing smartphones and other devices that use smaller OLED screens. As the technology allows better and larger displays, you may start seeing them in places you would never have been able to find a screen before. OLEDs also allow individual pixels to be turned completely off, letting viewers see true black.

Last editorial update on Jan 24, 2020 11:35:37 am.

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Sources

  • Angelle, Amber. "Will LED Light Bulbs Best Your CFLs and Incandescents?" Aug. 2010. (Jan. 6, 2020). http://www.popularmechanics.com/science/environment/will-led-light-bulbs-best-cfls-and-incandescents
  • EarthEasy. "LED Light Bulbs: Comparison Charts." (Jan. 7, 2020). https://learn.eartheasy.com/guides/led-light-bulbs-comparison-charts/
  • LEDs Magazine. "Fact or Fiction: LEDs Don't Produce Heat." May 10, 2005. (Jan. 9, 2020). https://www.ledsmagazine.com/leds-ssl-design/thermal/article/16696536/fact-or-fiction-leds-dont-produce-heat
  • Morrison, Geoffrey. "LED Local Dimming Explained." CNET. March 26, 2017. (Jan. 8, 2020). https://www.cnet.com/news/led-local-dimming-explained/
  • Scheer, Roddy and Moss, Doug. "The Dark Side of LED Lightbulbs." Scientific American. Sept. 15, 2012. (Jan. 7, 2020) https://www.scientificamerican.com/article/led-lightbulb-concerns/

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