Coe-Sullivan holds a prototype quantum dot display; such displays emit extremely pure colors and could eventually be scaled up to compete with conventional screens. (Photo credit: Porter Gifford.)

Seth Coe-Sullivan, chief technology officer at Watertown, MA, startup QD Vision, fastens alligator clips to two edges of a transparent wafer the size of a cell-phone screen and flips a switch: a rectangle filling the center of the wafer suddenly turns from reflective silver to faint red. A lab worker turns off the room lights to heighten the effect -- but this isn't necessary. Coe-Sullivan turns a knob and the device begins glowing brilliantly.

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