Have you seen the movie “Minority Report”? Have you been astonished by the transparent computer screens that Tom Cruise used? If yes, you’ll marvel at what German researchers come up with now: OLED (organic light emitting diode) pixels that are entirely transparent. The researches, working at the Technical University of Braunschweig, state to be the first in the world to have developed this technology.
In order to get transparent OLED pixels they use transparent TFTs (thin-film transistors) that are made of a 100-nanometer-thick layer of zinc-tin-oxide. Those are known for transmitting more than 90 percent of visible light. On the contrary LCDs (liquid crystal displays), made of silicon as most transmitters, are absorbing most light. The German researches now came up with the idea to position the TFTs and the OLED pixels next to each other in the transparent display. They won’t be any interference, not even if the OLED pixel is placed on top of the TFT driver circuit.
Since the TFT layers are thin, it is possible to deposite them on large areas with conventional techniques at temperatures below 200 degrees Celsius. For that reason cheap and flexible plastic substrates can be used. Another impressive fact is the brightness: Whereas typical computer screens make it up to a brightness of approximately 300 candelas per square meter, the devices developed by the researchers can reach up to 700 candelas per square meter.
All components of transparent OLEDs are transparent (substrate, cathode and anode). A transparent OLED display that is turned on allows light to pass in both directions. For it can be either active- or passive-matrix it can be used for heads-up displays. The substrate of top-emitting OLEDs is either opaque or reflective, wherefore they suit best to active-matrix design.
Transparent OLED Displays
Samsung Mobile Display showcased a 14 inch transparent AMOLED Display for notebook PCs at CES-2011. It comes in a resolution of qFHD 960×540 pixel (78PPI) and has a panel with a transmissivity of 40 percent.
Samsung Mobile Display shows the world’s first large transparent AMOLED Display prototype, designed for use in applications from PC monitors to TVs at the CES-2011.
Whether the prototype AMOLED display is turned off or on, it maintains up to a 30 percent transparency. The average transparency of comparable devices has been below 10 percent.
SMD’s transparent AMOLED prototype provides the highest resolution on a transparent large screen TV (over 19 inches) or monitor display.