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Scale-up Chemical Synthesis of Thermally-activated Delayed Fluorescence Emitters Based on the Dibenzothiophene-S,S-Dioxide Core
Published on: October 24, 2017
Hybridized local and charge transfer dendrimers with near-unity exciton utilization for enabling high-efficiency
Yixiao Yin1, Songkun Zeng1, Chen Xiao1
1Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Engineering Laboratory of Light-Electricity-Heat Energy-Converting Materials and Applications, School of Materials Science & Engineering, Changzhou University, Changzhou 213164, China. qiji830404@hotmail.com.
Researchers developed new dendrimers that combine hot exciton and thermally activated delayed fluorescence processes. This breakthrough achieves nearly perfect exciton utilization efficiency for highly stable and efficient organic light-emitting diodes (OLEDs).
Area of Science:
- Materials Science
- Organic Electronics
- Photophysics
Background:
- Achieving high emission efficiency and exciton utilization efficiency (ηS) in hot exciton materials remains a significant challenge in organic electronics.
- Hot exciton materials offer potential for enhanced light emission, but practical applications are hindered by efficiency limitations.
Purpose of the Study:
- To propose and demonstrate a novel strategy for enhancing exciton utilization efficiency (ηS) in hot exciton materials.
- To design and synthesize novel dendrimers capable of exhibiting both hot exciton behavior and thermally activated delayed fluorescence (TADF).
Main Methods:
- Synthesis and characterization of two novel dendrimers, D-TTT-H and D-TTT-Bu, featuring diphenylamine donors and tri(triazolo)triazine acceptors.
- Investigation of photophysical properties including emission efficiency, hot exciton processes, and TADF characteristics using theoretical calculations and various spectroscopic techniques (transient photoluminescence, magneto-electroluminescence, transient electroluminescence).
- Fabrication and performance evaluation of solution-processable organic light-emitting diodes (OLEDs) utilizing the synthesized dendrimers as dopants and sensitizers.
Main Results:
- The synthesized dendrimers D-TTT-H and D-TTT-Bu exhibit high emission efficiency (~80%) in solution and demonstrate simultaneous hot exciton and TADF characteristics in the solid state.
- Achieved nearly unity exciton utilization efficiency (ηS) due to the synergistic effect of hot excitons and TADF.
- OLED devices fabricated with these dendrimers showed excellent performance, including high luminance (15090 cd m⁻²) and maximum external quantum efficiency (EQEmax) of 11.96% as dopants.
- When used as a sensitizer, D-TTT-H enabled EQEmax values of 30.88% (green), 24.08% (orange), and 14.33% (red) in solution-processed OLEDs.
Conclusions:
- The proposed strategy of regulating singlet-triplet energy difference to induce an additional TADF process is effective for enhancing ηS in hot exciton materials.
- The novel dendrimers represent a significant advancement in designing fluorescent molecules for high-performance and stable OLED applications.
- This research opens new avenues for developing efficient and robust fluorescent materials for next-generation organic electronic devices.
