Sharp announced that it has developed, in collaboration with NHK, a 30" rollable 4K OLED panel on an IGZO backplane. This is a direct emission OLED, which sharp says is the world's largest ever produced (LG's OLEDs all use color filters).
Sharp's OLED panel is deposited on a thin-film substrate, and has a thickness of 0.5 mm. The display uses NHK's signal processing and panel driving technologies to "improve the brightness uniformity and video clarity".
Sharp started commercial production of smartphone OLED displays in low volume in August 2018, but recent reports suggested that as Sharp understands it cannot compete with Korean and Chinese companies with both technology and price it has decided to stop production. It could be that now Sharp is aiming to divert its efforts to medium or large sized OLED panels.
I am not sure but I think that Samsung OLED TV in 2013 were direct emission RGB OLED (no color filters), and at the time was available in 55-inch...
Therefore, my understanding would be that they were the world largest direct emission OLED displays...
The Sharp 30-inch rollable direct emission OLED display may however be the world largest ROLLABLE display that use direct emission OLED...