New research from the School of Advanced Materials, Peking University Shenzhen, focuses on developing stable and efficient solution-processable deep-blue OLEDs using multiple resonance (MR) type emitters. The authors designed three new deep blue emitters by introducing methyl and adamantyl groups as end-capped moieties to enhance device stability. The end-capped modification stabilizes the excited states by reducing vibronic couplings in the molecular backbones. The adamantyl groups also improve the stability of the emissive layer, as confirmed through morphology studies of the blend films.
The solution-processed deep blue OLED based on the m-DABNA-AdCz emitter achieved impressive performance, with a high current efficiency of 6.0 cd/A and a narrow emission spectrum (full-width at half-maximum of 21 nm), resulting in a pure blue color coordinate of (0.133, 0.076). Remarkably, the device demonstrated a long lifetime (LT95) of 55.7 hours at an initial luminance of 1000 cd/m2, which is the best reported lifetime for solution-processed OLEDs with a CIE y-coordinate below 0.08.
The authors emphasize the importance of developing stable solution-processable emitters, particularly deep-blue emitters, for cost-effective and energy-efficient OLEDs. Solution-based fabrication techniques offer advantages such as cost-effectiveness, simplified processes, and the ability to cover large areas compared to vacuum thermal evaporation. However, solution-processed OLEDs often exhibit lower stability due to faster aggregation of guest molecules under electrical stress. This research presents a viable strategy for developing high-performance solution-processed deep blue fluorescent OLEDs with high color purity and long device lifetime by utilizing end-capped modification to stabilize excited states and enhance emissive layer stability.
Reference
Li, H., Yan, H., Zhang, X., Shi, K., Kuang, C., Zheng, X., He, Y., Meng, L., Xu, H., Meng, Z., Yan, C., Wei, G., Zhu, Y., & Meng, H. (2024). Highly efficient and stable solution-processed deep-blue OLEDs with LT95 over 50 h at 1000 nit. Chemical Engineering Journal, 150142. https://doi.org/10.1016/j.cej.2024.150142
