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.Experimental devices using the technology have also achieved brightness levels of up to 700 candelas per square meter (cd/m²), compared to only around 300 cd/m² for traditional LCD displays. Despite this, the technology allows production with conventional techniques and at low temperatures, enabling the use of "cheap, flexible plastic substrates." Thomas Riedl, a research head at the University of Braunschweig, says working transparent OLED prototypes will be available in only two years, although he did not give an estimate for eventual shipping products. Thanks to Ars Technica for the tip.
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.