Compared with liquid crystal displays, these light-emitting polymers have big advantages. Glowing ink Ghassan Jabbour, a physicist at the University of Arizona, is experimenting with screen printing techniques to lay OLEDs down on films. He thinks a screen that can be rolled or folded is on the way. Another way of making screens might be to use ink-jet printers. That's what Cambridge Display Technology and Seiko Epson of Nagano showed in July, when they demonstrated colour screens made of light-emitting polymers.
Passive matrix is easier.
The intersections of a grid of ultrafine wires are used to make an array of individual addressable electrodes. And a blob of red, green or blue-glowing polymer at each intersection forms each pixel. The trouble is that the influence of each pair of electrodes tends to spread beyond a single pixel, creating a slightly fuzzy image and limiting the density of pixels. Active matrix displays are better. They depend on arrays of transistors laid out beneath the screen, with each transistor controlling a single pixel.