We don't usually post about OLED concepts, but here's an interesting design: a mobile phone that uses a 'double-display' which is an OLED display on top of an E Ink display, and both are transparent. You can switch between the displays: so when power is low, you can use the E Ink to conserve battery. A nice touch is that if you're using the E Ink display, the degree of transparency of the display shows how much battery is remaining. The more transparent the display, the less battery remaining. Nice.
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This is pretty far reaching, and we're not sure if it's possible to create a transparent E Ink. But maybe a nice touch is the 'more transparent the display is, the less battery remaining'. Perhaps it can be used in OLEDs as well: the less power, the less bright the OLED is...