As one of the core components of organic display and lighting technology, blue organic light-emitting diodes (OLEDs) have always faced the dual challenges of efficiency and stability. The current commercially available blue OLED has relatively low performance and requires technological breakthroughs to improve its efficiency and longevity. Thermally activated delayed fluorescence (TADF) materials have attracted extensive attention due to their pure organic and high efficiency. However, it is still difficult for TADF materials to meet commercial requirements in terms of stability, especially in the blue light region. Therefore, researchers have been exploring how to improve the efficiency and stability of TADF materials.
The team of Professor Duan Lian and Assistant Researcher Dongdong Zhang from the Key Laboratory of Organic Optoelectronics and Molecular Engineering of the Ministry of Education at Tsinghua University is committed to improving the performance of blue OLEDs. For the first time, they succeeded in replacing all hydrogen atoms in the Tadf molecule with deuterium atoms by adopting an all-deuterium substitution strategy, so as to improve the efficiency and lifetime of blue Tadfoled devices. Through this research, it is hoped that the performance of the existing blue phosphorescent OLED can be surpassed and bring new development opportunities to the field of OLED display and lighting.
In this study, the research team successfully developed a fully deuterated blue Tadf molecule by replacing all the hydrogen atoms in the Tadf molecule with deuterium atoms by hydrothermal synthesis methods. The core idea of this strategy is to reduce the vibrational coupling by suppressing the high-frequency vibration of the molecule, reduce the radiation-free transition rate and the dissociation probability of chemical bonds, so as to improve the external quantum efficiency and lifetime of the device. In addition, the fully deuterated molecules can also achieve blue shift and narrowing of the emission spectrum, and improve the energy transfer rate, so as to realize the fabrication of deep blue light TADF devices with high color purity. Through detailed photophysical characterization of the fully deuterated and non-deuterated molecules, the research team found that the fully deuterated molecules had significant improvements in photoluminescence quantum yield, photochemical stability, and fluorescence resonance energy transfer efficiency.
Experiments have verified that the maximum external quantum efficiency of the fully deuterated TADF molecule in the sensitized device reaches 331%。In addition, the device lifetime of the fully deuterated TADF molecule has been significantly improved, from 1000 Cd M2 initial brightness (LT80) to 1365 hours. Compared with non-deuterated OLED devices, the device performance of the fully deuterated TADF molecule is significantly improved and surpasses the phosphorescent material (BD-02) reported by Samsung in South Korea. Through the TSF strategy, the research team has also successfully achieved the fabrication of deep blue light TADF devices with high color purity.
This research work not only provides new perspectives for the design and optimization of TadF molecules, but also opens up a new path for the realization of more efficient and stable blue OLED devices. The successful development of fully deuterated TADF molecules will further promote the development of organic light-emitting technology, which is of great significance for the industrial application of blue-light TADF materials. In the future, researchers will continue to explore the application of TADF molecules and fully deuterated TADF molecules in OLED devices, further improve the efficiency and stability of the devices, and promote the commercialization of this technology.
Blue OLED technology is one of the important research directions in the field of organic light-emitting technology. The research team of Professor Lian Duan and Assistant Researcher Dongdong Zhang from the Key Laboratory of Organic Optoelectronics and Molecular Engineering of the Ministry of Education of Tsinghua University has made important progress in the field of blue tadfoled through the all-deuterium substitution strategy. They have successfully developed high-efficiency and stable blue-light TADF devices using fully deuterated TADF molecules. This research brings new opportunities for the development of blue OLEDs and lays the foundation for the realization of more efficient and stable organic light-emitting devices. The research results have been published in the journal Nature Photonics.
The first author of the study is Dr. Tianyu Huang from the Department of Chemistry at Tsinghua University, and the co-corresponding authors are Assistant Researcher Dongdong Zhang and Professor Lian Duan from the Department of Chemistry at Tsinghua University. The research team also includes Qi Wang, Hai Zhang, Yuewei Zhang and others from the Department of Chemistry at Tsinghua University, as well as Dr. Zhan Ge from the School of Chemistry and Molecular Engineering at Peking University. The research was supported by the National Natural Science Outstanding Youth Program and the National Key R&D Program of the Ministry of Science and Technology.
Through the all-deuterium substitution strategy, the research team successfully replaced all hydrogen atoms in the TADF molecule with deuterium atoms. This strategy effectively suppresses the high-frequency vibration of molecules, reduces the radiation-free transition rate and the probability of chemical bond dissociation, and thus improves the external quantum efficiency and lifetime of the device. The maximum external quantum efficiency exhibited by the fully deuterated TADF molecule in the sensitized device is 331%, the lifetime of the device is increased to 1365 hours. Compared with non-deuterated OLED devices, the device performance of fully deuterated TADF molecules has been significantly improved, and surpassed the phosphorescent materials reported by Samsung in South Korea.
Through a detailed analysis of the photophysical properties of the fully deuterated and non-deuterated molecules, the research team found that the all-deuterated molecules had significant improvements in photoluminescence quantum yield (PLQY) and photochemical stability. In addition, it was also found that the fully deuterated molecules could achieve blue shift and narrowed emission spectra, thereby increasing the energy transfer rate and realizing the fabrication of deep blue TADF devices with high color purity.
This study has made an important breakthrough in the field of blue tadfoled through the all-deuterium substitution strategy. The development of fully deuterated TADF molecules not only improves the efficiency and lifetime of blue Tadfoled devices, but also provides a new direction for the further development of organic light-emitting displays and illumination. The achievement of this research result will promote the commercialization of blue OLED technology and contribute to the realization of more efficient and stable organic light-emitting devices.
In the future, the research team will continue to explore the design and optimization of TADF molecules to further improve the performance of blue Tadfoled devices. They will continue to study the fully deuterated TADF molecule and its application in devices, explore more new materials and technologies, and promote the development of organic luminescence technology. At the same time, they will also work to solve the problem of stability of TADF materials, further improve the lifetime of devices, and realize the commercial application of organic light-emitting technology.