>>106324040
are you talking about LCD? that essentially works by selectively blocking a white backlight but process is not 100% efficient so some inevitably leak. OLED is made up of very small LEDs, which are not lit if the color is pure black. Of course, there's bound to be and inherent energy cost of driving the display but it would be safe to assume that it would be negligible when compared to a screen in use at 50% brightness