A team of researchers from the Hong Kong Polytechnic University, Eastern Institute of Technology in Ningbo, Sichuan University and a number of other Chinese research centers has created a new type of flexible OLED panels that can be stretched almost like rubber while maintaining the brightness of conventional displays.
The problem with displays is that conventional materials quickly crack and lose conductivity when stretched. To avoid this, one needs to solve two challenges at the same time: making the luminous layer flexible and creating an electrode that can withstand deformation. The Chinese scientists have proposed a simple and rigorous solution: they mixed a light-emitting polymer with an elastic material that has properties similar to rubber.
The key component was SBS elastomer, a synthetic rubber with hard and soft regions, in which the former provide strength and the latter provide stretchability. This enables the material to undergo significant deformation and return to its original state. Within the mixture, SBS is distributed in the form of microscopic inclusions, bearing the brunt of the mechanical load.
This results in a uniform structure: the polymer creates channels for charge transfer, while the soft regions of the SBS act as shock absorbers, relieving stress during stretching.
With the addition of SBS, the stretchability of the material almost doubled, and its performance characteristics improved: charge loss decreased, resulting in a more than threefold increase in electron current, while luminescence efficiency rose by some 6%. This directly affects energy consumption: the lower the losses and the higher the efficiency, the less energy is required to achieve the same brightness.
The second major component of the new development was electrodes. Instead of the fragile materials used in conventional displays, the scientists used a network of silver nanowires. To improve its reliability, the network was embedded in an elastic film and additionally coated with a conductive layer. This design proved to be flexible, smooth and stable: it withstands repeated stretching and retains its properties for a long time. Reduced resistance in these electrodes also lowers energy losses during operation.
As a result, the researchers successfully created a fully stretchable OLED. Its brightness reaches some 33,000 cd/m², which is comparable to conventional displays. Moreover, the device can be stretched more than twice its original size without losing functionality. Even after hundreds of stretching cycles, it retains about 90% of its original brightness, which can be considered an outstanding result.
This solution by the Chinese scientists brings us closer to the era of flexible electronics and so-called electronic skin (stretchable devices that can operate directly on the surface of the body), but also has direct implications for energy efficiency. Improved luminous efficiency and reduced charge losses mean that such displays can consume less energy while maintaining the same brightness. In the context of the rapid growth of wearable devices and screens, this becomes an important factor in reducing the load on energy systems.
