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Weekly UpdatesRecently, improvements in LCD TV have provided substantial advantages to consumers. One improvement is in the area of LED backlighting. This improvement alone has increased image quality with respect to contrast and color. Additional benefits of LED backlighting is in the reduction in power consumption and the reduction in thickness of TVs.
Plasma televisions have been claiming higher contrast than LCD TVs in dark environments but with the use of LED backlight and image adaptive dimming, this advantage is gradually being lost. The color gamut of RGB-LED-lit LCD TV is the highest of all types of TVs including OLED TV. OLED panels are supposed to be thin because there is no backlight involved. The 11-inch OLED TV on the market is quoted to be 3-mm at the thinnest point of the set. "Even if the OLED panel is only 3-mm thick, the TV will need to be 25-mm or so--we are getting close to that with LCD technology," said Samsung in December 2008.
In fact, the thickness of recent models of LCD TVs is likely to be far less than 25-mm. This is true for LED-lit LCD-TV as long as the backlight is fabricated in the "edgelit" mode. But the edge-lit mode does not provide the advantage of high color gamut. In the "direct-lit" mode of LED backlight, OLED TV has the advantage of slimness but has to face stiff competition in power consumption because of "image adaptive dimming" employed in "direct-lit" mode.
Having said this, the competition in power consumption that OLED TV has to face is not that simple even with "edge-lit" mode of LCD TV because of the impressive efficacy of white LEDs employed in "edge-lit" mode. Plasma TV will also face stiff competition in terms of power consumption.
In December 2008, an 11-inch OLED TV by Sony consumed power of around 45W. Recent development of 46-inch LCD TVs employing "image adaptive dimming" has demonstrated power consumption of 50W. So with the introduction of LED-lit LCD TV, the power consumption has been substantially dropping.
"White pixel" approach is another route available for both OLED technology and LCD technology to further decrease power consumption. What is significant here is that OLED technology has the inherent advantage of the absence of backlight. Under this condition, one would normally expect a significant drop in power consumption and a low price. But it is not happening in the real world.
Any new technology takes time to reveal its full potential in the marketplace. OLED technology has the potential of low power consumption through its well demonstrated "harvesting of triplet states." The materials developed in the phosphorescent OLED family have demonstrated even 200,000 hours at lab level except for blue-emitting material. Blue is still a problem even at lab level. In terms of low cost of manufacturing, solution-based processes and "roll-to-roll" manufacturing processes hold the key in OLED technology. None of these are validated at the commercial level in mass manufacturing.
A substantial learning curve in large-area OLED mass manufacturing will start with the introduction of 32-inch and larger OLED TVs. Establishing an infrastructure similar to LCD will be capital intensive. In addition to all these barriers, LED backlight is imposing another barrier to the adoption OLED screens.
Both OLED and LED also have potential applications in lighting. The R&D and manufacturing activity in LED is far higher than OLED. Big giants like GE, Osram and Philips are taking the lead in LED lighting. The price of LEDs is coming down substantially. Experimental efforts are underway to introduce six-inch wafers in mass manufacturing and low-cost substrates including glass. Low power white LEDs in mass manufacturing have shown efficacy as high as 150 lm/w and lab level demonstration for white has revealed 247 lm/w. Medium power white LEDs have shown mass manufacturing level efficacy of 110 lm/w.
What is important is that the efficacy of LEDs is in higher range of brightness compared to OLED. OLEDs also have demonstrated 100 lm/w at lab level but not yet at the manufacturing level. It appears that LED efficacies are not saturating. This is likely to keep pressure on OLED TV and plasma TV.
Samsung, AUO, ChiMei, LG Display, Sony, Sharp and Panasonic are all in LED/LCD TV development and are exploiting LED backlight for low power consumption and enhancement in image quality. Sony and Samsung are leading in OLED manufacturing with Sony leading in OLED TV. Samsung is delaying introduction of large-size OLED TVs. All other things being equal (with LCD), theoretically OLED technology should be advantageous both from the price angle and power angle. But this advantage is being delayed due to the pressure from LED backlighting.
The one area where OLED holds an advantage is in its potential to have "roll-to-roll" manufacturing resulting in flexibility, slimness and low weight. In this aspect there will not be any threat from LCD TV or plasma TV. But it will take a minimum of 10 years for this to happen.
--Munisamy Anandan is president and managing member of Organic Lighting Technologies LLC, an optical component manufacturer. He is a senior member of IEEE and delivered the keynote address on "LED Backlight for LCD" at the International Display Research Conference in Moscow.
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