Researchers have enhanced the performance of blue Thermally Activated Delayed Fluorescence (TADF) Organic Light Emitting Diodes (OLEDs) by innovatively applying a honeycomb patterned porous polystyrene (PS) film directly onto the devices as an external light extraction layer. Utilizing the cost-effective “breath figure” (BF) method, the study capitalizes on the condensation of water droplets in a controlled humidity environment to form a porous structure. By varying the polymer concentration and the humidity, the researchers were able to tailor the morphology of the honeycomb-patterned (HCP) PS films, achieving an optimal balance of pore diameter and height that significantly enhances light extraction.
The results showed a remarkable improvement in the OLEDs’ performance, with current efficiency increasing by 53% to 31.05 cd/A and power efficiency by 21% to 16.31 lm/W. Furthermore, simulations using the Finite-Difference Time-Domain (FDTD) method revealed that achieving a height/diameter (H/D) ratio close to 1.0 in the HCP PS films offers the best trade-off for enhancing light extraction, among other factors such as pore distribution and refractive index differences. This straightforward yet effective strategy, which avoids the complexities of traditional light extraction enhancement methods, not only provides a deeper understanding of the mechanisms behind light extraction efficiency but also offers a practical approach for boosting the performance of OLED devices.
Referemce
Zheng, Y., Zhang, Q., Yang, X., Chen, Y., Zhao, B., Zheng, H., Li, X., Kabe, R., & Chen, L. (2024). Performance improvement of blue thermally activated delayed fluorescence organic light emitting diodes via in-situ fabricated honeycomb porous polystyrene pattern. Optics and Lasers in Engineering, 177, 108137. https://doi.org/10.1016/j.optlaseng.2024.108137
