Breakthrough in Flexible OLED Technology
Researchers from Drexel University and Seoul National University have successfully developed flexible and stretchable organic light-emitting diodes (OLEDs). This advancement could lead to improvements in mobile technology displays and facilitate the creation of wearable technology, such as on-skin sensors capable of real-time monitoring of temperature, blood flow, and pressure.
Key Innovations and Design
The new OLED technology integrates a flexible, phosphorescent polymer layer with transparent electrodes made from MXene nanomaterial. This combination enables the OLEDs to be stretched up to 1.6 times their original size while largely retaining their luminescence. This innovation addresses a significant challenge in flexible OLED technology: the durability of luminescence after repeated mechanical stress.
- Exciplex-assisted phosphorescent (ExciPh) layer: This intrinsically stretchable organic layer enhances charge union and exciton creation, improving light production efficiency. It allows over 57% of excitons to produce light, significantly higher than the 12-22% efficiency of current emissive materials with polymer layers.
- Thermoplastic polyurethane elastomer matrix: Added to further improve the stretchability of the ExciPh layer.
- MXene-based electrodes: High-quality, conductive, transparent, and stretchable electrodes combine MXene, a two-dimensional nanomaterial, with silver nanowires. These electrodes optimize charge injection into the ExciPh layer, ensuring the OLED maintains its luminescence while being flexed or stretched.
Overcoming Previous Limitations
Existing flexible OLEDs, while capable of folding and bending, have shown degradation in pixel brightness and flexibility over time due to the materials used in their electrodes and organic layers. Traditional methods to make conducting materials flexible often compromise charge transport and light emission. The new MXene-contact stretchable electrodes offer high mechanical robustness and tunable work function, ensuring efficient charge injection and preventing brittleness.
Performance and Applications
The research team created green OLED displays and demonstrated their performance under strain and repeated use. The device's performance decreased by only 10.6% at 60% of its maximum strain. It also retained 83% of its light production efficiency after 100 cycles of 2% strain, indicating improved durability compared to current OLEDs. Researchers at Seoul National University also produced a full-color, fully stretchable display and passive-matrix OLEDs to showcase broader applicability.
This technology is expected to play a crucial role in developing next-generation wearable and deformable displays, real-time healthcare monitoring, and advanced wearable communications technology. Future research will focus on optimizing substrate materials, color production, and streamlining the manufacturing process.