OLED displays have burn-in problems because the blue diode is significantly less durable than the red and green, about 1000x weaker, so the blue diode needs to be driven quite hard at a high current density, at which point the quantum efficiency falls off very severely. Current 3rd gen OLEDs have 16% external quantum efficiency. The blue emitter is unstable. Phosphorescent OLEDs (2nd gen) are what all the physicists and engineers trying to figure out how to get working (it's very hard - things like doping the emission layer with heavy metals is restricted by the EU - their environmental laws and LCD marketing is what killed the CRT), which might be in 6-8 years, since those have halflives 100x greater than the current 3rd gen fluorescent organic diodes. OLEDs are horribly complex, there's a lot of quantum mechanics in them.