Stretching Crystals Promise Bendy, Full-Color Displays
NewScientist is reporting that a new approach to crystal formation could help create power-efficient, flexible color displays. These new photonic crystals, structured similar to opals, can be tuned by adjusting the gaps between the crystals. "The beauty of the device is that it can produce the whole spectrum of colors, even ultraviolet and infrared light, using only incident light. As a result, the expensive color filters used in every other color display on the market today, are no longer needed. And because the displays use only reflected ambient light, no power is wasted on back-lighting, as in today's mobile phones, for example. 'They can be viewed just as well in bright sunlight as in indoor light,' team member André Arsenault of the University of Toronto told New Scientist."
This is a very good point and I think it would be interesting if you integrate a photocell into the devices. When the photocell detects enough ambient light, you can turn the backlight off, but when there is no light, or very low light, you turn the backlight on, or possibly even dim it up and down. This way it can function in varying degrees of ambient light, but can also save a significant amount of energy.
However the reflection effectively acts like an absorption if viewed transmissively. So if you had a backlight, you could tune the effective absorption band of each individual pixel. By cutting out a band of colors (and using adjacent pixels), you effectively have full color control.
So it's possible to imagine a future version of this tech where the display is normally reflective (black backing) but when required switches to emissive display (which would require a backlight turning on, and inverting the logic of the display pixels so that the colors don't come out inverted). Thus you'd have the "best of both worlds."