If you've seen the movie "Minority Report" and marvelled at the transparent computer screens used by Tom Cruise, you'll appreciate what German researchers have concocted in their labs: entirely transparent OLED (organic light emitting diode) pixels.

The researchers, located at the Technical University of Braunschweig, are claiming the development to be a world's first.

Their approach is to use transparent TFTs (thin-film transistors) made of a 100-nanometer-thick layer of zinc-tin-oxide, which transmits more than 90 percent of visible light. Such transistors are more often made of silicon, which is used for LCDs (liquid crystal displays) but is highly absorptive in the visible part of the spectrum.

In the transparent displays, the TFTs and the OLED pixels are positioned next to each other. The OLED pixel can be placed on top of the TFT driver circuit without interference.

In addition, because the TFT layers are thin, they can be deposited on large areas with conventional techniques, and because these techniques can be performed at temperatures below 200 degrees Celsius, cheap, flexible plastic substrates can be used.

In the devices developed by the researchers, the brightness of the OLED pixels varied from 0 to 700 candelas per square meter by changing the voltage of the driving TFTs. By comparison, typical computer screens today reach a brightness of approximately 300 candelas per square meter.

Transparent OLEDs have only transparent components (substrate, cathode and anode) and, when turned off, are up to 85 percent as transparent as their substrate. When a transparent OLED display is turned on, it allows light to pass in both directions. A transparent OLED display can be either active- or passive-matrix. This technology can be used for heads-up displays. Top-emitting OLEDs have a substrate that is either opaque or reflective. They are best suited to active-matrix design. Manufacturers may use top-emitting OLED displays in smart cards.

CES-2010 World first Notebook with 14 inch transparent OLED Display

Samsung Mobile Display showed the world first and largest transparent OLED panel prototpye at CES-2010.

Samsung SDI Co Ltd showcased the "Window Display," an OLED panel with a transparent of 30%. The company used four 12.1-inch Window Displays to make a "window".The resolution of the panel is 840 ×504, and its luminance is 200cd/m2. The color reproduction range is 100% of the NTSC standard. The response time is 0.01ms.