Direct-emission OLEDs do not use color filters. Each pixel is made from RGB sub-pixels.
Doping is a technical concept or new technology in the semiconductor industry to improve and increase the performance of different devices. In the case of most of the conventional OLEDs, charge transport is inefficient due to the poor conductivity of transport layers (both hole and electron transport layers). With doping technology, the conductivity of transport layers can be increased by orders of magnitude; one can create highly efficient OLEDs with low driving voltage.