A team at Philips Research Laboratories (Eindhoven, Netherlands) has succeeded in making a 64 x 64-pixel display in which each pixel is driven by a thin-film transistor (TFT) based on a polymer semiconductor. While the display is still currently made on a glass screen, the incorporation of polymer electronics is an important step toward the realization of low-cost, all-polymer, flexible displays. The ultimate market for these includes high-information-content products such as the flexible electronic newspaper.
The active matrix is a method of addressing an array of liquid-crystal cells, one cell per monochrome pixel, allowing the screen to be refreshed more rapidly. The Philips display operates at switching frequencies as high as 100 Hz. In conventional systems, the active matrix is made using amorphous-silicon-based TFTs and represents a major part of the cost of the display. In the new system, each of the 4096 pixels of the demonstrator active-matrix display is switched by its own TFT based on a polymer semiconductor; at present only the semiconductor part of the transistors consists of polymer, and the transistors are made on a solid substrate. All-polymer transistors on flexible substrates have been demonstrated already by the same group of researchers. All-polymer TFTs are currently being incorporated in the next prototype flexible display.
Polymer-based active-matrix systems offer a major advantage in lower-cost production methods, as fewer production steps and less stringent clean-room conditions are required. It is also possible, in principle, to print the switches on plastic foil in a reel-to-reel process. The resulting matrix of switches can be very large in size. This brings high-volume, flexible display systems a step closer.