Question What causes banding in OLEDs?

[BrightLight2019]

I apologize if this has been addressed elsewhere. I've done a Google search for the exact phrase used in the topic title, but I'm exclusively finding threads complaining about/comparing severity of banding, none explaining WHY it happens.

I'm not very knowledgeable when it comes to TV tech, but I'm having trouble understanding what causes banding in OLED screens. I understand with LCD TVs, you can have uneven lighting and blotchiness in the picture due to issues with the backlight diffuser, uneven pressure on the screen, placement of the backlights, and problems during manufacturing.

What I can't figure out is why OLED vertical banding appears. If each pixel is turned on or off individually, I'm having trouble understanding why large portions of the screen might appear darker or brighter than the surroundings. I would have assumed that if it were to occur, it would be on a pixel-by-pixel basis spread somewhat evenly across the screen. Explaining it to me as though I were ten years old, what is the mechanism behind this?

My other question involves why banding persists as the screen ages. With OLEDs, I understand that the pixels dim and decay as they are used. If patches of the screen are consistently lit less brightly then their neighbors, wouldn't the darker portions of the screen age less quickly and the brighter portions of the screen age more quickly, causing the picture to even out over time? However, this doesn't appear to be the case, at least not in a time frame that would matter to most OLED owners. Why doesn't vertical banding correct itself?

If anybody has a not-too-technical explanation for the causes of vertical banding in OLEDs and why the problem doesn't correct itself over time, I'd love to hear it.

 

[encaser]

Turning them on usually.

 

[Light30M]

the panel has to be given power equally, and that's where OLED fails time to time to deliver equal power to each pixel.
As to why it happens is because pressure during manufacturing on a microscopic scale on the panel gives variance between each pixel. this causes tints and vertical banding and even vignetting.

 

[Keiron]

Tell me you're kidding - you get banding on OLEDs? I'm right now about to jump into the market for an OLED and one of the main reasons I'm moving on from plasma is because of the banding which I thought OLEDs didn't suffer from.

Tell me this isn't true?

 

[staffy 2]

Well I had the most perfect E7 and for 14 months I never saw one band ever.After the second 2000 hour compensation cycle it introduced bands but luckily they cleared up after approx 100 hours.In the last week they’ve appeared again more pronounced but aren’t spoiling my veiwing.Id say as the panels age it causes banding.Ive a five year warranty with Peter Tyson who I’ve always found to be good but it’s only in certain content I see bands and they are feint so it’s not an issue as yet and hopefully they’ll clear up again.
Why do bands suddenly appear on a perfect panel,can anyone help explain this.