Researchers located at the Technical University of Braunschweig, claim to have developed the first transparent OLED pixels. Their approach was to use transparent TFTs (thin-film transistors) made of a 100-nanometer-thick layer of zinc-tin-oxide, which transmits more than 90% of visible light.
In the transparent displays, the TFTs and the OLED pixels are positioned next to each other or even on top of each other with no distortion or 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.
By changing the voltage of the driving TFTs, the brightness of the OLED pixels varied from 0 to 700 candelas per square meter. By comparison, typical computer screens today reach a brightness of approximately 300 candelas per square meter.
Project manager from the Technical University of Braunschweig, Thomas Riedl, estimates that prototype displays could be available as early as 2008.