The development of multi-resonance organic electroluminescent materials has greatly advanced the progress of organic light-emitting diode (OLED) panels for achieving ultra-high-definition displays. Thanks to the strong molecular rigidity and alternating frontier orbital distribution of multi-resonance luminescent materials, such materials have the advantages of narrow-band emission and high luminescent quantum efficiency. However, due to the short-range charge transfer characteristics within the molecules, the development of highly efficient narrow-band pure red light-emitting materials presents a significant challenge compared to blue and green light.
In response to the above issues, a "donor-enhanced synergistic conjugation extension" strategy was proposed by the team of Professor Chuluo Yang and Professor Xiaosong Cao from Shenzhen University. This strategy achieved spectral tuning from orange-red light to pure red light to deep red light and efficient narrow-band emission. The prepared pure red light OLED device achieved the BT.2020 red light standard (CIE = 0.701, 0.298), and exhibited a maximum external quantum efficiency and current efficiency of up to 32.5%/20.2 cd A-1. This work is a further extension of the "double boron/nitrogen/oxygen" multi-resonance narrow-band red light molecular design strategy proposed by this research group in 2022 (Adv. Mater. 2022, 34, 2201442). Specifically, this work achieved precise control of red light by reasonably replacing the carbazole unit in the traditional carbazole-based emitter CzCzBNO with a stronger electron-donating and more conjugated multi-ring aromatic 5-phenyl-5,10-dihydroindolo[3,2-b]indole moiety. While maintaining molecular rigidity and the multi-resonance electron structure characteristics, the precise control of red light was achieved through frontier orbital engineering. Furthermore, the integration of high color purity and efficiency of red emitter was achieved through "asymmetric" molecular design.
Recently, a research paper titled "Precise Modulation of Multiple Resonance Emitters toward Efficient Electroluminescence with Pure-Red Gamut for High-Definition Displays" was published online on July 28, 2023, in the prestigious chemistry journal Science Advances. This work received strong support from the National Natural Science Foundation of China, the Guangdong Provincial Committee of Basic and Applied Basic Research, and the Shenzhen Municipal Science and Technology Innovation Committee. Please refer to the following link for the full text：https://www.science.org/doi/10.1126/sciadv.adh8296.
