According to a report from TheElec in Korea, Apple is looking at several tandem OLED architectures to apply to future iPhone AMOLED displays.
Apple is using a tandem OLED architecture for its iPad Pro devices, where each sub pixel is doubled vertically to increase performance. LG Display, which supplies most of these tandem AMOLEDs to Apple, is now suggesting a new architecture in which only the blue emitter is stacked, while the green and red are not. This will increase performance, but will not be as expensive as a fully tandem device.
LG refers to this stack as a simplified tandem OLED. It is understood that Apple is interested in this technology, and has also asked Samsung Display to suggest a similar display. LG Display seems to be leading over Samsung in its tandem OLED R&D (and other key areas as well).
LG Display recently announced plans to invest $925 million to advance its OLED R&D in the next two years, and it is likely that such architectures are part of the R&D drive.