How Does This Flexible Display Stack Up?
Engineers have created a flexible, skin-like OLED display that outperforms existing technologies and can power on-body and foldable screens.
Not long ago, displays were heavy, bulky, power-hungry, and relatively expensive due to the cathode-ray tube technology that was required for their operation. This limited where and when they could be used, keeping them largely confined to desks, kiosks, and other permanent installations. But with the rise of LED-based display technologies, they became small, inexpensive, and highly portable. These days there are digital displays wherever we look — even in our pockets.
But one frontier that has not been conquered yet is in the area of flexible displays. Flexible displays have many applications that traditional, rigid screens cannot accommodate, like on-body displays and foldable screens that make it possible to carry around a large display in a small package. This is not to say that flexible displays do not exist, of course. They certainly do, however, present technologies are fraught with problems.
As it stands today, flexible displays have issues with long-term durability, and they also have resolution issues as the screens flex. These devices are typically made with a grid of side-by-side organic thin-film transistors (OTFTs) and organic light-emitting diodes (OLEDs). The OLEDs supply the light, while the OTFTs control their operation, but give off no light. As a display is flexed, the OTFTs — as well as the connecting wires — are exposed. This leaves nonluminous gaps between the pixels. This makes for a poor aperture ratio, and therefore a bad experience for the user.
A group of engineers at the Northeast Normal University in China have come up with a proposed solution to this problem. Their display design repositions the OTFTs and OLEDs such that the aperture ratio is significantly enhanced. That means that minimal gaps open up between pixels during flexing, which makes for a much clearer, higher-resolution display and a better user experience.
To make this possible, the team designed the pixels such that they are arranged in vertical stacks of components. Each stack consists of an OLED, all of the interconnects, and the necessary OTFTs. These stacks are then laminated together for mechanical strength. Displays are then made out of a matrix of these pixels, such that there is no appreciable gap to open up between them as the screen flexes.
Experiments demonstrated that these displays have excellent mechanical properties. They could easily bend and flex to closely conform to the human body, for example. Crucially, this technology enabled the aperture ratio of a pixel to reach 83 percent, which is superior to any other flexible display presently in existence. The durability of the screen also looks to be promising, with it holding up quite well after enduring 10,000 folding cycles.
Because the displays are built with commonly used components, it should not be too difficult to fabricate them at scale. Given this factor, and the previously unseen levels of performance exhibited by the screens, the researchers hope that their technology will soon power the next generation of portable and wearable electronics.
