Researchers at the University of Chicago Pritzker School of Molecular Engineering have found a surprisingly simple way to improve stretchable organic light-emitting diodes, or OLEDs. By adding a common plastic softener to light-emitting polymer films, the team simultaneously increased their brightness and stretchability, addressing two properties that have been difficult to achieve together, tells this Tech Xplore article.
Stretchable OLEDs could play an important role in wearable electronics, humanoid robots, 3D displays, biosensors, and body-compatible electronics. The challenge is creating materials that remain soft and flexible without sacrificing their ability to emit light efficiently.
The researchers focused on thermally activated delayed fluorescence, or TADF, polymers. Although these materials can be highly efficient emitters, their polymer chains can pack too closely together. This causes concentration quenching, in which neighboring units interfere with one another, and energy is lost before it can produce light.
The team tested dioctyl phthalate, or DOP, a commercially available plasticizer commonly used to soften materials such as vinyl. Adding DOP created additional space between the polymer chains. This reduced unwanted interactions while allowing the chains to move more easily when stretched.
The improvement was substantial. The fluorescence efficiency of the TADF film increased from 60% to nearly 100%, approaching its theoretical maximum. Its crack-onset strain rose from only 5% to more than 110%. When incorporated into working OLED devices, the plasticized films delivered a 35% improvement in efficiency compared with devices without DOP.
Importantly, the method also worked with four other TADF polymers featuring different chemical structures. This suggests the technique could offer a broadly applicable alternative to developing customized chemical structures for individual emitters.
Led by undergraduate researcher Glingna Wang, the study points toward a simpler route to high-performance stretchable displays. The researchers are now integrating the materials into display arrays and investigating applications in optical therapies and other light-based biomedical technologies.