A new process for making monolayer semiconductors—a flexible, molecule-thin film that has low light absorption thus making it a promising technology for transparent displays—has given the technology a brighter future.
By introducing an organic superacid to the process, researchers at the University of California-Berkeley found a way to increase the film’s photoluminescence quantum yield, a ratio measuring light output versus the amount of energy put in, by 100 fold. More importantly, the superacid helped produce a cleaner, less-defective film which previously had been plaguing monolayer semiconductor technology.
“Traditionally, the thinner the material, the more sensitive it is to defects,” principal investigator Ali Javey, a professor of electrical engineering and computer sciences and a faculty scientist at Berkeley Lab, told Phys.org. “This study presents the first demonstration of an optoelectronically perfect monolayer, which previously had been unheard of in a material this thin.”
Researchers envision that this type of perfect monolayer will play a major role in the development of high-performance transparent LED displays.
A monolayer semiconductor film shaped into a Cal logo. The image on the left shows the material before it was treated by the superacid; the right hand image is the film after the treatment. Image by Matin Amani / UC Berkeley
What does this mean for the product cycle?
Transparent display technology has been around for a decade or two, but only in the past few years has it been incorporated into consumer items. The most commonly produced types of see-through displays are OLED screens, which use an organic film that generates its own light—the same kind of film that the Berkeley engineers are working to improve.
Some current model mobile phones like the Samsung Galaxy Note 4 and Motorola Moto X use OLED screens. OLED displays can be found in tablets as well—in the Galaxy Tab S series, for example. Larger format displays also use OLED technology, like the LG 55” 4K OLED display. These examples have OLED screens housed on the same chassis that you might find a LCD or LED display. The color brilliance and darker blacks of OLED are detectable to the eye, but otherwise look similar to their backlit LCD counterparts.
Transparent displays at this point are mostly relegated to prototype models used for tradeshow eye candy. The Samsung Smart Window won the CES Innovation Award in 2012. It is actually a traditional LCD display that uses ambient light for a backlight and a special transparent backlight unit that acts as a light when it is dark outside. We have yet to see the Smart Window come to market.
The transparent LCD displays currently available on the market and are relegated to ultra high-end applications. “If you just wanted a transparent display for your desktop it would be a couple thousand bucks,” says Jay Patterson, CEO of Taptl, a St. Louis-based transparent display maker. “If you wanted us to manufacture a complete kiosk or replace an office window with the transparent display—that would cost a little more, as we need to engineer the installation.”
Taptl’s patent-pending transparent screen is light-agnostic and self-contained. The startup has found market entry selling to yacht manufacturers.
“Right now we have transparent LCD, which is great for its intended purpose,” Patterson says. “Transparent OLED is the holy grail of transparent display technology.” He estimates that the technology will become mainstream in the next five years.
It will be interesting to see how science behind the Berkeley Labs break though affects the product timeframe for transparent OLED displays. Ultimately it is up to how industry forces adopt the technology. Samsung and LG have in the past collaborated with OLED patent holders Universal Display Group in their product development. How this technology comes to market will depend on how these companies continue to work together.
