Originally Posted by fafrd
Do any of the OLED gurus on the board understand what the impact of agong OLED layers will be in a WOLED stacked architecture (especially blue)?
Time-to-half-brightness of Blue is supposed to be ~30,000 hours.
So after 30,000 hours use of a specific subpixel on a WOLED, does that mean light output will remain similar to what it is on a new subpixel but composition of white light output of the aged subpixel will have shifted away from blue and more strongly towards red/green (yellow)?
Or will total light output of an aged subpixel decrease in addition to a shift in whitepoint towards yellow?
On a more detailed level, as blue OLED materials age, does their effective 'resistnce' remain constant and it is just the light ouput efficiency generated by a similar current that decreases or does the effective 'resistance' of the blue material increase so that current level for a given voltage decrease (or voltage level required for a desired current increases) and is does efficiency of blue light generated from that reduced current level the same or does efficiency decrease in addition?
We're starting to get first user reports of WOLED TVs exceeding 2500 hours and approaching 5000 hours and I'm trying to understand what the expected impact of aging OLED layers should do to light output as use starts getting into the range of blue half-life specifications...
Found the attached graph.
It indicated that for 30,000 hour half-life (brown 20 mA/cm^2 curve), light output is reduced by ~10% after ~1000 hours).
And I've seen some reports that LG is claiming a 100,000 hour lifetime for their WOLED TVs (purple 10 mA/cm^2 curve) which would indicate that light output is reduced by about 5% after 1000 hours...).
The Wiki page on OLEDs indicates that the aging process involves loss of light generation efficiency only, so as an OLED ages through use, light output decreases while current/resistance remains roughly constant.
We've got several users who watch what many would consider to be excessive display of a TV/cable channel or two with static logo components reporting that they are experiencing signs of burn-in after ~500 hours of display of those static logos (25% - 40% of their viewing).
Those subpixels, especially for yellow/orange/red logos are getting 500 hours of repeated saturated use while surrounding subpixels are getting used as little as 1/16th that level (1 of 4 random colors at random intensity level).
These aging curves are convincing me that if you have a cluster of subpixels experiencing 500-1000 hours of high-saturation use while the overal panel subpixels of the same color are experiencing only 30-65 equivalent hours of use, that difference is likely to show up as subpixels whose light output is darker by ~5-10%...
Could this be behind the several reports of burn in by heavy TV/cable single-channel users we are seeing?