A couple of months ago, Samsung release the Galaxy S5 LTE-A, that sports the company's latest AMOLED panel - a 5.1" QHD (2560x1440) Super AMOLED. Anandtech posted a long review of this new phone, and they find that the display is actually a little bit more efficient than the 5.1" FHD panel used in the GS5, even though it sports a higher resolution (which usually means a less efficient display as the aperture ratio gets smaller.
Anandtech further says that Samsung told them they switched to a new, improved emitter material for the new QHD panel, which explains the increased efficiency. This is interesting as the QHD display was released only a few months after Samsung started producing the FHD panel, which by itself was 27% more efficient than the previous generation panels - also due to more efficient OLED materials.
In April it was reported that Samsung's Cheil Industries (now Samsung SDI) announced it will start supplying Samsung Display with phosphorescent green host for their OLED displays. It was suggested that these new host may be more efficient than UDC's own green hosts. There's no evidence that this is so, however (Cheil's hosts are supposedly cheaper than UDC's). But now it is specifically reported that Samsung adopted new emitter materials. UDC mentioned a few months ago that Samsung switched to a new green PHOLED emitter, but it was thought that this was for the FHD display.
So it may be the Samsung adopted another new PHOLED emitter (maybe a new red, or an ever newer green) from UDC. Or it may be that they adopted a better fluorescent blue. Or it may be that this report is simply not accurate and Samsung's new emitter comment relates to the original FHD panel used in the GS5.
Disclaimer: the author of this post holds share in UDC