An LED-backlit LCD is a liquid-crystal display that uses light-emitting diodes (LED) for backlighting instead of cold cathode fluorescent lamps (CCFL). LED-backlit displays use the same TFT (thin-film transistor) LCD technologies as CCFL-backlit LCDs, but offer a variety of advantages over them. The LED bulbs are typically blue or white, but more recently RGB ones have been developed. There are four types of LED-backlit LCDs: Edge-Lit, Direct-Lit, Full-Array Local Dimming (FALD) and Mini-LED, each describing how the LED bulbs are arranged behind the liquid-crystal display for illumination. A variant is QLED, a type of LED-backlit LCD that uses an extra layer film of quantum dots for improved color gamut.
Televisions that use a combination of an LED backlight with an LCD panel are sometimes advertised as LED TVs, although they are not truly LED displays. They largely replaced CCFL-backlit LCD TVs in sales and manufacture by the early 2010s.
Backlit LCDs of any type cannot achieve true blacks for pixels, unlike the totally self-emissive OLED and MicroLED displays. This is because even in the "off" state, black pixels still allow some light from the backlight through. Some LED-backlit LCDs use local dimming zones to increase contrast between bright and dim areas of the display, but this can result in a "blooming" or "halo" effect on dark pixels in or adjacent to an illuminated zone.
Comparison with CCFL-backlit LCDs Advantages When compared with earlier CCFL backlights, using LEDs for backlighting offers:
Wider color gamut (with RGB-LED or QDEF)Dell Studio XPS 16: Highest Color Gamut Ever?. Anandtech.com, 26 February 2009Competing display technologies for the best image performance; A.J.S.M. de Vaan; Journal of the society of information displays, Volume 15, Issue 9 September 2007 Pages 657–666; http://onlinelibrary.wiley.com/doi/10.1889/1.2785199/abstract? and dimming rangeDimming options for LCD brightness; J. Moronski; Electronicproducts.com; 3 January 2004; http://www.electronicproducts.com/Optoelectronics/Dimming_options_for_LCD_brightness_control.aspx Greater contrast ratio Very slim (some screens are less than thin in edge-lit panels) Significantly lighter and cooler, as much as half the total chassis and system weight of a comparable CCFL Typically 20–30% lower power consumption and longer lifespan Greater reliability
Disadvantages
Light is not evenly lit thus creating potential bright hot spots or dark patches on a screen
LED arrangements
LED backlights replace CCFL (fluorescent) lamps with a few to several hundred white, RGB or blue LEDs. An LCD with LED-Backlight may be edge- or direct-lit:
edge-lit (ELED): LEDs form a line around the rim of the screen. May additionally support: frame dimming: adjusts the brightness of the entire backlight based on the content displayed, as if local dimming was supported but only with a single zone local dimming: multiple vertical or horizontal zones are individually controlled direct-lit (DLED) or full-array: LEDs form an array directly behind the screen at equally spaced intervals. May additionally support: frame dimming: adjusts the brightness of the entire backlight based on the content displayed, as if local dimming was supported but only with a single zone local dimming: multiple direct-lit LED clusters (rectangles) are individually controlled. Commonly referred to as Full Array Local Dimming (FALD).
Additionally a special diffusion panel (light guide plate, LGP) is often used to spread the light evenly behind the screen.
The local dimming method of backlighting allows to dynamically control the level of light intensity of specific areas of darkness on the screen, resulting in much higher dynamic-contrast ratios, though at the cost of less detail in small, bright objects on a dark background, such as star fields or shadow details.Scott Wilkinson. "Ultimate Vizio ". UltimateAVmag.com. Posted Fri 29 May 2009. Retrieved 16 December 2009.
A 2016 study by the University of California (Berkeley) suggests that the subjectively perceived visual enhancement with common contrast source material levels off at about 60 LCD local dimming zones.David M. Hoffman, Natalie Stepien, Wei Xiong "Implications of the number of local dimming zones and native LCD contrast on visual quality of HDR displays
In 2025 RTINGS.com found in accelerated longevity tests that edge-lit TVs were more prone to quicker failure than direct-lit panels (especially during non-stop usage) due to the heat of the LEDs being more concentrated and intense than direct-lit panels, making them more prone to panel cracking and warping and thus LED burnouts and failures.
Technology LED-backlit LCDs are not self-illuminating (unlike pure-LED systems). There are several methods of backlighting an LCD panel using LEDs, including the use of either white or RGB (Red, Green, and Blue) LED arrays behind the panel and edge-LED lighting (which uses white LEDs around the inside frame of the TV and a light-diffusion panel to spread the light evenly behind the LCD panel). Variations in LED backlighting offer different benefits. The first commercial full-array LED-backlit LCD TV was the Sony Qualia 005 (introduced in 2004), which used RGB LED arrays to produce a color gamut about twice that of a conventional CCFL LCD television. This was possible because red, green and blue LEDs have sharp spectral peaks which (combined with the LCD panel filters) result in significantly less bleed-through to adjacent color channels. Unwanted bleed-through channels do not "whiten" the desired color as much, resulting in a larger gamut. RGB LED technology continues to be used on Sony BRAVIA LCD models. LED backlighting using white LEDs produces a broader spectrum source feeding the individual LCD panel filters (similar to CCFL sources), resulting in a more limited display gamut than RGB LEDs at lower cost.
Using PWM (pulse-width modulation), a technology where the intensity of the LEDs are kept constant but the brightness adjustment is achieved by varying a time interval of flashing these constant light intensity light sources,Dimming options for LCD brightness; J. Moronski; Electronicproducts.com; 3 Januari 2004; http://www.electronicproducts.com/Optoelectronics/Dimming_options_for_LCD_brightness_control.aspx the backlight is dimmed to the brightest color that appears on the screen while simultaneously boosting the LCD contrast to the maximum achievable levels, drastically increasing the perceived contrast ratio, increasing the dynamic range, improving the viewing angle dependency of the LCD and drastically reducing power consumption.
The prismatic and reflective polarization films are generally achieved using so called DBEF films manufactured and supplied by 3M.Brochure 3M Display Materials & Systems Division Solutions for Large Displays: The right look matters; http://multimedia.3m.com/mws/media/977332O/display-materials-systems-strategies-for-large-displays.pdfBroadband reflective polarizers based on form birefringence for ultra-thin liquid crystal displays; S.U. Pan; L. Tan and H.S. Kwok; Vol. 25, No. 15; 24 July 2017; Optics Express 17499; https://www.osapublishing.org/oe/viewmedia.cfm?uri=oe-25-15-17499&seq=0 These reflective polarization films using uniaxial oriented polymerized liquid crystals (birefringent polymers or birefringent glue) were invented in 1989 by Philips researchers Dirk Broer, Adrianus de Vaan and Joerg Brambring.Polarisation-sensitive beam splitter; D.J. Broer; A.J.S.M. de Vaan; J. Brambring; European patent EP0428213B1; 27 July 1994; https://worldwide.espacenet.com/publicationDetails/biblio?CC=EP&NR=0428213B1&KC=B1&FT=D#
The white LEDs in LED backlights may use special silicate phosphors, which are brighter but degrade faster. The size of the LEDs is one of the factors that determines the size of the bezel of LED-backlit LCDs.
Because LEDs can be switched on and off more quickly than CCFLs and can offer a higher light output, it is theoretically possible to offer very high contrast ratios. They can produce deep blacks (LEDs off) and high brightness (LEDs on). However, measurements made from pure-black and pure-white outputs are complicated by edge-LED lighting not allowing these outputs to be reproduced simultaneously on screen.
Power consumption and eco-credentials The evolution of energy standards and the increasing public expectations regarding power consumption made it necessary for backlight systems to manage their power. As for other consumer electronics products (e.g., fridges or light bulbs), energy consumption categories are enforced for television sets. Standards for power ratings for TV sets have been introduced, e.g., in the US, EU, Australia,"EU Australia and US regulation on energy consumption in TV sets", 2008 and China."China Regulation on Energy Consumption in TV Sets", 2010 A 2008 study"International survey on the importance of the energy efficiency of TV appliances", 2008 showed that among European countries power consumption is one of the most important criteria for consumers when they choose a television, as important as the screen size.Controlling Power Consumption for Displays With Backlight Dimming; Claire Mantel et al; Journal of Display Technology; Volume: 9, Issue: 12, Dec. 2013; https://ieeexplore.ieee.org/document/6520956
LED-backlit LCDs have longer life and better energy efficiency than plasma and CCFL LCD TVs. Unlike CCFL backlights, LEDs do not use mercury in their manufacture, which is an environmental pollutant. However, other elements (such as gallium and arsenic) are used in the manufacture of the LED emitters; there is debate over whether they are a better long-term solution to the problem of screen disposal.
The combination of LED dynamic backlight controlMethod of and device for generating an image having a desired brightness; D.A. Stanton; M.V.C. Stroomer; A.J.S.M. de Vaan; US patent USRE42428E; 7 June 2011; https://worldwide.espacenet.com/publicationDetails/biblio?CC=US&NR=RE42428E in combination with reflective polarizers and prismatic films (invented by Philips researchers Adrianus de Vaan and Paulus SchaaremanIllumination system and display device including such a system; A.J.S.M. de Vaan; P.B. Schaareman; European patent EP0606939B1; https://worldwide.espacenet.com/publicationDetails/biblio?CC=EP&NR=0606939B1&KC=B1&FT=D&ND=5&date=19980506&DB=EPODOC&locale=en_EP# make these "LED" (LCD) televisions far more efficient than the previous CRT-based sets, leading to a worldwide energy saving of 600 TWh in 2017, equal to 10% of the electricity consumption of all households worldwide, or twice the energy production of all solar cells in the world.Energy Efficiency Success Story: TV Energy Consumption Shrinks as Screen Size and Performance Grow, Finds New CTA Study; Consumer Technology Association; press release 12 July 2017; https://cta.tech/News/Press-Releases/2017/July/Energy-Efficiency-Success-Story-TV-Energy-Consump.aspx LCD Television Power Draw Trends from 2003 to 2015; B. Urban and K. Roth; Fraunhofer USA Center for Sustainable Energy Systems; Final Report to the Consumer Technology Association; May 2017; http://www.cta.tech/cta/media/policyImages/policyPDFs/Fraunhofer-LCD-TV-Power-Draw-Trends-FINAL.pdf
Methods A first dynamic "local dimming" LED backlight was publicly demonstrated by BrightSide Technologies in 2003,H. Seetzen, et al.: "A High Dynamic Range Display System Using Low and High Resolution Modulators", SID03 Digest and later commercially introduced for professional markets (such as video post-production). Edge LED lighting was first introduced by Sony in September 2008 on the BRAVIA KLV-40ZX1M (known as the ZX1 in Europe). Edge-LED lighting for LCDs allows thinner housing; the Sony BRAVIA KLV-40ZX1M is 1 cm thick, and others are also extremely thin.
Full-array mini-LED backlights, consisting of several thousand WLEDs, were being researched for TVs and mobile devices in 2017.