- The full article entitled “Tuning Ternary Deep Red Exciplex‐Forming Hosts to Achieve a Stable OLED with EL Peak Centered at 834 nm” can now be found at the Advanced Optical Materials website at https://advanced.onlinelibrary.wiley.com/doi/10.1002/adom.202501258
- Authors: Yi-Yun Chen, Yu-Cheng Kung, Cheng-Han Tsai, Chun-Kai Wang, Dian Luo, Yi-Sheng Chen, Shun-Wei Liu,* Allen Chu-Hsiang Hsu, Wen-Yi Hung,* and Ken-Tsung Wong*
Near-infrared (NIR) light is especially valuable because of its ability to penetrate biological tissues, making it highly promising for applications in bioimaging, photodynamic therapy, sensing, and communications. Yet developing efficient organic light-emitting diodes (OLEDs) that shine beyond 800 nanometers has long been a challenge. The main obstacles are fundamental energy-loss processes—such as those dictated by the energy gap law—and fluorescence quenching that occurs when too many light-emitting molecules are packed together.
To overcome this barrier, Professor Ken-Tsung Wong’s team at the Department of Chemistry, NTU, has pioneered a new strategy using ternary exciplexes as the host material in NIR OLEDs. By carefully combining the electron acceptor 58p-QN and the donor CPF, the team first created a deep-red OLED that emits at 696 nanometers. They then introduced a finely tuned spacer material, TPF, to match this emission with the absorption of a specialized NIR molecule, iCzPBBT. This step maximized energy transfer while minimizing losses. Finally, by doping iCzPBBT into the emission layer at low concentrations, the device harnessed Förster resonance energy transfer (FRET) to push the emission deeper into the NIR region at 834 nanometers. Impressively, the device reached an external quantum efficiency of 1.72% and demonstrated a lifetime of over 88 hours under continuous operation at low current density.
This breakthrough highlights the unique advantages of ternary exciplexes for both efficient energy transfer and stable long-wavelength emission. More importantly, it opens up fresh design pathways for NIR OLEDs—showing that with smart molecular design and precise control of interactions, it is possible to achieve devices that are not only efficient but also durable. These results lay an important foundation for future NIR light sources in fields ranging from biomedical diagnostics to optical sensing and next-generation night-vision displays.
