Researchers, located at the Technical University of Braunschweig, are claiming a world first in having developed transparent Organic Light Emitting Diodes (OLED).
Applications for these are huge, with obvious choices being for overlays for use with existing items, such as HUD built into the windscreen of your car or screens that could give surgeons additional information without obstructing their view. Think of the transparent displays from the movie Minority Report.
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 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.
Depositing techniques for building the transparent display can be performed at temperatures below 200 degrees Celsius, which means cheap, flexible plastic substrates can be used.
Thomas Riedl, head of the organic and inorganic lasers team of the High-Frequency Institute at the Technical University of Braunschweig expects the first prototype transparent OLED displays to be available in two years.
