When Samsung launched the Galaxy S5, DisplayMate tested the new display (a 5.1" FHD, 432 PPI, Super AMOLED) and found it to not only be the best mobile display ever tested at Displaymate, but also 27% more efficient than the 5" Full-HD one on the GS4. Samsung told DisplayMate that the improvement mostly came from more efficient OLED materials, but they never told us which materials exactly.
During a recent investors conference, Universal Display revealed that the GS5 uses their new red emitter material, and the company says that "Samsung attributes the increase in power efficiency" to the new emitter. This is rather surprising as I wouldn't have thought a new red emitter can effect the power efficiency of the whole display so dramatically.
Perhaps the truth is somewhere in the middle - the 27% efficiency boost resulted from several new materials, one of them being the new red emitter. I guess we'll never know for sure, but one thing is for certain - OLEDs are advancing rapidly on all display parameters.