The U.S. Army is testing a prototype “watch” that’s lightweight and thin and has a full-color display. This display is built on flexible materials encased in a rugged plastic case and can be worn on a wristband to display streaming video and other information. It uses newly developed phosphorescent materials that are efficient at converting electricity into red, blue, and green light, which means the display needs less power to work.
Most phones, laptops, and TVs today use liquid-crystal displays (LCDs) controlled by electronics built on glass. To make more energy-efficient displays that are controlled by flexible electronics, which are lightweight and won’t shatter like glass, many companies are turning to organic light-emitting diodes (OLEDs). The pixels in OLED displays replace the layers of electronics and filters in LCDs with organic dye molecules that emit light in response to electrical current.
For consumers, flexible OLEDs promise portable electronics with beautiful screens that don’t drain battery life and won’t shatter when dropped. But so far, no companies have developed economically viable manufacturing methods for producing flexible OLEDs with long enough lifetimes and consistent quality. The U.S. military has been funding development with the aim of providing soldiers with rugged, thin communications devices that can display maps and video without adding too much weight to their load.
The new display prototypes use efficient OLED materials developed by Universal Display of Ewing, New Jersey, and are built on foil-backed electronic controls developed by LG Display, headquartered in Seoul, South Korea. The devices were designed by L-3 Display Systems of Alpharetta, Georgia. The display is 4.3 inches. As part of military demonstration tests, the device has been used to stream real-time video from unmanned air vehicles.
“These prototypes represent not so much one major advance but continued progress on many fronts,” says Janice Mahon, vice president of technology development at Universal Display. Those fronts include the OLED materials themselves, the electronics that control them, and the integration and packaging of the device.
The first generation of OLED materials, used today in glass-backed cell-phone displays and some small TVs, can convert only 25 percent of electrical current into light; the rest is lost as heat. Universal Display is designing and developing materials that work by a different mechanism and that have a theoretical efficiency of 100 percent. The prototypes for the Army use a full set of phosphorescent materials; the companies have not released specifications about power consumption, but Mahon says displays made with these materials use one-fourth the power of a conventional OLED.