OLED TVs: Technology Advancements Thread - Page 12

Well, here's some Samsung prime beefsteak OLEDs, sizzlin' on da grill. Images are full-size and are linked to source article.

[Breaking Down OLED TV] 2 TFTs Used per Subpixel? [Part 9]
26 December 2007





The Nikkei Electronics Breakdown Team finished measuring the display properties of Sony's OLED TV. Next, we moved on to observe the pixel structure in detail with the help from a panel engineer.

An active matrix OLED panel generally uses a TFT in the drive circuit. In contrast to an LCD panel that uses a TFT only as a switch, an OLED panel uses a TFT as an analog device to control the luminance. Thus, the variation in TFT properties is directly related to the unevenness of the luminance.

Panel manufacturers proposed a various kinds of ingenious drive circuits to cope with the problem of uneven luminance resulting from the variation in TFT properties. Many of them proposed to use three to four TFTs in each subpixel to build a correction circuit.

The latest OLED TV was highly valued by the panel engineer for its "extremely low luminance variation." What kind of pixel structure is employed in the panel?

The observation revealed that two TFTs seemed to be used per subpixel. They were believed to be provided as switching and driving devices, constituting the simplest structure. Does the TV correct the luminance variation outside the panel?

Because the TV only uses two TFTs, it has a higher pixel aperture ratio over the product using more TFTs. The Nikkei Electronics Breakdown Team estimated that the latest panel has an aperture ratio of about 75%, which is considerably high. It is likely that Sony prioritized the enhancement of aperture ratio in the designing to fully utilize the emitting material whose life is not adequately long.

Sony said to be seeking strategic partners to produce and sell OLED panels
23 January 2008

In order to expand the OLED TV market, Sony, which released the world's first OLED TV last year, is looking for strategic partners to cooperate in the production and sales of OLED panels, according to a Chinese-language Commercial Times report.

The report also cited Taiwan-based Topology Research Institute (TRI) as saying shipments of OLED TVs will rise from nearly 4,000 units in 2007 to 3.75 million units in 2012. While Digitimes Research recently estimated that shipments of OLED TVs will grow from 2,000 units in 2007 to 18,000 units in 2008, while further shooting up to 50,000 units in 2009 and 120,000 units in 2010.

During the recently completed CES 2008 show in Las Vegas, Samsung Electronics also showcased two (14.1-and 31-inch) OLED TV models, with the company stating it will begin commercial production of mid- to large-sized OLED TVs around 2010.

Your 10-lumen-per-watt plasma tech doesn't yet exist, while OLED does. I've noticed that there is a constant stream of talk about it on this forum, yet if you read carefully the announcements of plasma manufacturers, it is a dream on their future timelines; it is what they hope for. Not what physics says you can actually get out of a UV-excited phosphor.

Personally, I don't think they will get that kind of efficiency; even if they do, it will not dispose of the flicker or PWM artifacting, or burn-in. It is a stalling tactic to try to stem the tide of the market's broad acceptance and uptake of LCD and potentially, OLED products.

Turning back again to the PDP manufacturers' development of these technologies: most are unlikely to reach production stage, because they increase the display cost. Right now PDP costs cannot compete with LCD and thus PDP is losing market share. Why would manufacturers even think of widening the loss gap by increasing their costs? Only Pioneer has done so; they have made themselves into a shining example for their fellow PDP makers on how to commit economic suicide. A review of their latest financial data will easily substantiate this statement.

Of course the paper you linked to is Panasonic propaganda; though it does have some interesting information, using it as a reference guide for future market predictions would be unwise.

Indeed competition is good, but that's not going to stop me from stating my opinion on PDP technology. I believe that PDP as an economic product is doomed; first by LCD and next by the subject of this thread, OLED. The advantages of OLED are too many, and its potential easily great enough to surpass PDP.

PDP is just an absurdly inefficient way of doing what OLED does directly. The inherent quantum inefficiency of indirect stimulation (electrons -> gas -> UV -> phosphor) cannot even today compete with the efficiency of OLED (electrons -> light). Worse still, the high voltage necessary to ionize gas will forever be a hobble to PDPs as it rquires expensive, high-energy circuitry to run. I could go on but this post is about more than just the deadfalls of PDPs.

And if you think 10 Lu/W is efficient, remember that a 100W incandescent (those bulbs that are getting restricted and soon to be banned in some countries due to their gross inefficiency) gets 16 Lu/W, and 4' T8 triphosphor fluorescent 80-90 Lu/W, and metal halide 100+. In other words, PDP is less efficient than the lowliest of illuminants, a blackbody radiator (tungsten filament). Even if they could double the efficiency, it would still be miles from what OLED can achieve, and will likely fall below LCD technology of the same time frame.

The major limitation on LCD efficiency is the polarizer, which rejects 50% or more of the light. Unless a method is developed to efficiently rotate light's polarization within a small space, that is unlikely to change. One possible solution is to develop BLU LEDs which emit polarized light, eliminating the need for a polarizer.

Here is a link to polarized LED information:

POLARIZED LED

Regarding SAH, it is not a defect but a positive attribute; flicker causes headaches, and a significant fraction of individuals can see it. Both fully held and short duty-cycle and schemes in-between have their values, depending on the use. However, not all technologies can support these different modulation schemes.

The pixels' temporal duty cycle can be varied between a very small value and completely on with OLED. PDP cannot, as it is currently designed, support continuous discharge because gas ionization is nonlinear, which is why it uses on/off PWM to obtain grayscales. That is an inherent defect of the technology, which is based on its fundamental construction and thus cannot be removed. Gas ionization works a certain way, and all the wishing in the universe won't change that.

It is possible to pulse the PDP's PWM faster to make the flicker less visible (or even invisible) but running circuits at all three: high voltage, high frequency, and high power, is a guarantee that you'll also get the other three: high cost, short life, high operating temperature.

- High cost is infeasible (see Pioneer) because of LCD competition (direct and indirect);

- Short life is infeasible because lifetimes are already too short and LCDs last longer;

- Hotter electronics can't be done because the electronics already run too hot and have a relatively high failure rate, much higher than LCD.

There is no leeway for making the situation any worse in any of these three points, because LCD has it beat in all of them.

The OLED emitter runs at low voltage, meaning electronics that are cheap, low-voltage, and low-energy (like LCD). This means low operating temperature, and thus long lifetimes and high reliability.

Depending on its design, OLED can be fully held like LCD or flicker at 60 Hz. like PDP, or anywhere in-between. OLED emitters don't have the nonlinear characteristic of PDP's gas-fill.

Finally, OLED can do something neither LCD nor PDP can: it can run at hundreds or thousands of frames per second, since the emitter has a response time in the microsecond range. This allows a third alternative, rather than the duality of SAH/flicker: using interpolation or a high-speed external signal, it can show flicker-free silky smooth motion.

Today while thinking on the subject, I realized that if all the work that has been put into patching PDP and LCD with band-aids to mitigate their inherent defects, had instead been spent on OLED development, we would probably be able to buy 32" or larger OLEDs today.

This is not to say that such work has been a total waste, but both roads are dead-ends so the massive fixed infrastructure investment was likely ill-advised, unless it can be cheaply converted for future display production. At the moment LCD fabs are likely to be able to make OLEDs, but PDP production is just too different to make a retrofit economically feasible. The PDP makers are truly alone right now, as they have no other road to travel but the one they are on; one that ends in a clearing not too far away.