Thermally activated delayed fluorescence (TADF) materials have attracted significant attention as organic light-emitting diode (OLED) materials due to their potential to achieve an internal quantum efficiency (IQE) up to 100%. In recent years, materials exhibiting a negative singlet-triplet energy gap (ΔE_ST), which is usually positive in most materials, have been investigated both theoretically and experimentally, as they are expected to exhibit fast intersystem crossing (RISC) from the triplet to singlet excited state and highly efficient luminescence.^1,2) HzTFEX₂ (Product No. H1933), a light-emitting material having heptazine structure, is the first material that was experimentally showed to exhibit delayed fluorescence from inverted singlet and triplet excited states (DFIST).³⁾ Such materials are also referred to materials with INVEST (inverted singlet-triplet gap).

Product

We offer HzTFEX₂, a light-emitting material under a license agreement.

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Physical Properties

HzTFEX₂ exhibits blue emission with the highest peak at 449 nm in toluene and a photoluminescence quantum yield (Φ_PL) of 74%. The ΔE_ST value was estimated to be -11 ±2 meV.³⁾

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Related Products

We also offer melem (Product No. M3538) and heptazine chloride (Product No. T4145), which are useful for the development of materials with heptazine structures.

Heptazine is known as a substructure of the graphitic carbon nitride (g-C₃N₄).^4,5) Graphitic carbon nitride is expected to be applied to various applications including photocatalysts and sensors due to its optical and semiconductor properties. In particular, its application as metal-free and visible light driven photocatalysts has attracted much attention, and the improvement of catalytic activity by metal doping or combination with other semiconductor materials has been investigated.⁶⁾ Porous photocatalysts such as covalent organic frameworks (COFs) composed of the heptazine structure have also been developed.⁷⁾ Thus, melem and heptazine chloride are useful not only for the light-emitting materials research but also for the research on the other photofunctional materials.

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References

1. 1) The Golden Age of Thermally Activated Delayed Fluorescence Materials: Design and Exploitation
   • J. M. Dos Santos, D. Hall, B. Basumatary, M. Bryden, D. Chen, P. Choudhary, T. Comerford, E. Crovini, A. Danos, J. De, S. Diesing, M. Fatahi, M. Griffin, A. K. Gupta, H. Hafeez, L. Hämmerling, E. Hanover, J. Haug, T. Heil, D. Karthik, S. Kumar, O. Lee, H. Li, F. Lucas, C. F. R. Mackenzie, A. Mariko, T. Matulaitis, F. Millward, Y. Olivier, Q. Qi, I. D. W. Samuel, N. Sharma, C. Si, L. Spierling, P. Sudhakar, D. Sun, E. Tankelevičiu̅tė, M. D. Tonet, J. Wang, T. Wang, S. Wu, Y. Xu, L. Zhang, E. Zysman-Colman, Chem. Rev. 2024, 124, 13736.
2. 2) The Role of Theoretical Calculations for INVEST Systems: Complementarity Between Theory and Experiments and Rationalization of the Results
   • Á. J. Pérez-Jiménez, Y. Olivier, J. C. Sancho-García, Adv. Optical Mater. 2025, 2403199.
3. 3) Delayed fluorescence from inverted singlet and triplet excited states
   • N. Aizawa, Y.-J. Pu, Y. Harabuchi, A. Nihonyanagi, R. Ibuka, H. Inuzuka, B. Dhara, Y. Koyama, K. Nakayama, S. Maeda, F. Araoka, D. Miyajima, Nature 2022, 609, 502.
5. 4) A critical review on graphitic carbon nitride (g-C₃N₄)-based materials: Preparation, modification and environmental application
   • J. Wang , S. Wang, Coord. Chem. Rev. 2022, 453, 214338.
6. 5) A Tour-Guide through Carbon Nitride-Land: Structure- and Dimensionality-Dependent Properties for Photo(Electro)Chemical Energy Conversion and Storage
   • V. W. Lau, B. V. Lotsch, Adv. Energy Mater. 2022, 12, 2101078.
7. 6) Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?
   • W.-J. Ong, L.-L. Tan, Y. H. Ng, S.-T. Yong, S.-P. Chai, Chem. Rev. 2016, 116, 2101078.
8. 7) Covalent Organic Frameworks Containing Dual O2 Reduction Centers for Overall Photosynthetic Hydrogen Peroxide Production
   • D. Chen, W. Chen, Y. Wu, L. Wang, X. Wu, H. Xu, L. Chen, Angew. Chem. Int. Ed. 2023, 62, e202217479.

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