55″ OLED HDTV on the Way?

Okay, I’m probably the last person to write about this topic, but there was so much noise and confusion that it took me a while to find a source who could give me the straight skinny. And I mean, really skinny!

You may have noticed stories saying that LG is going to come out with a 55″ OLED HDTV in 2012. Then there are others who say that’s wrong; LG is just going to be using white OLEDs as a backlight for LCD HDTVs instead of LEDs. Both say that these panels are going to be made on a Gen8 plant, however. At least that part is right, according to my sources.

Let’s start with what’s wrong about each rumor. An OLED HDTV using existing technology is problematic, at best. The amorphous silicon backplanes used for TFT LCDs do not have the electron mobility required for OLED displays. General wisdom holds that you need a polysilicon layer, which requires lasers to anneal the amorphous material to make crystals. But the laser annealing technology doesn’t work on substrates larger than about Gen 4.5 or so at this point. Gen 8 would present enormous challenges.

On the other hand, OLEDs don’t have the light output of LEDs and they are still rather expensive. Great strides are being made to create OLED solid state lighting panels, but it’s not likely that they will be big enough and inexpensive enough to replace LEDs in large screen LCD TVs by next year.

So what’s the truth? From what I’ve determined, LG is indeed working toward Gen 8 production of OLED panels. They expect to handle the material deposition in two passes per substrate, which is reasonable. The new wrinkle is that they are planning to use oxide TFTs to switch the pixels. This technology delivers sufficient electron mobility without the need for a polysilicon backplane.

Now, one fact that I haven’t seen mentioned in any of the stories on the subject (though I’m sure I haven’t seen them all) is that LG will be using white OLEDs. The light emitting layer will have red, green, and blue materials to create a white light. This will then get filtered through red, green, or blue filters over each sub-pixel. The Sony OLED also used white OLEDs with color filters, which means that the light output is reduced by at least two thirds. The LG design will be a bit brighter, however, because it will use a four sub-pixel pattern; in addition to the usual RGB, there will also be a white sub-pixel that will boost the light output of bright images.

The company is planning on production of the display panels before the end of this year, so we can reasonably expect to see sets by 2012. One of my sources also indicates that the company has not decided on the panel size (or sizes), but they are considering 40″ and larger panels.

I’d rather be right than first.