iOS 11 Dark Mode Confirms OLED For New iPhone Screens
Users trying the developer release of iOS 11 have discovered a systemwide dark mode, all but confirming an OLED display panel for the next iPhone. Enabled on accessibility settings, the smart invert feature is a clear precursor to a wider dark mode when the release reaches end users.
Dark mode is vital for OLED panels because of the way they work. Each pixel on the display is self lit, rather than relying on a backlight, as the LCD screen on a current iPhone does.
That means a black pixel is off and as a result consumes no power at all. In order to maximise battery life you want as many pixels off as often as possible. Hence dark mode.