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Highly Efficient Thermally Activated Delayed Fluorescence from Pyrazine-Fused Carbene Au(I) Emitters |
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| Authors: | Dr Jian-Gong Yang Xiu-Fang Song Dr Jian Wang Dr Kai Li Dr Xiaoyong Chang Li-Ying Tan Chu-Xuan Liu Fei-Hu Yu Prof Dr Ganglong Cui Dr Gang Cheng Dr Wai-Pong To Prof Dr Chuluo Yang Prof Dr Chi-Ming Che Prof Dr Yong Chen |
| Institution: | 1. Key Laboratory of Photochemical Conversion and Optoelectronic Materials &, CAS-HKU Joint Laboratory on New Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190 P. R. China
College of Materials Science and Engineering, Shenzhen University, Shenzhen, 518055 P. R. China;2. Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, Chemistry College, Beijing Normal University, Beijing, 100875 P. R. China;3. Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun, 130023 P. R. China;4. College of Materials Science and Engineering, Shenzhen University, Shenzhen, 518055 P. R. China;5. Department of Chemistry, Southern University of Science and Technology, Shenzhen, 518055 P. R. China;6. Key Laboratory of Photochemical Conversion and Optoelectronic Materials &, CAS-HKU Joint Laboratory on New Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190 P. R. China;7. Key Laboratory of Photochemical Conversion and Optoelectronic Materials &, CAS-HKU Joint Laboratory on New Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, 100190 P. R. China University of Chinese Academy of Sciences, Beijing, 100049 P. R. China;8. State Key Laboratory of Synthetic Chemistry, CAS-HKU Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P. R. China Hong Kong Quantum AI Lab Limited, 17 Science Park West Avenue, Pak Shek Kok, Hong Kong SAR, P. R. China;9. State Key Laboratory of Synthetic Chemistry, CAS-HKU Joint Laboratory on New Materials, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, P. R. China |
| Abstract: | Metal-based thermally activated delayed fluorescence (TADF) is conceived to inherit the advantages of both phosphorescent metal complexes and purely organic TADF compounds for high-performance electroluminescence. Herein a panel of new TADF Au(I) emitters has been designed and synthesized by using carbazole and pyrazine-fused nitrogen-heterocyclic carbene (NHC) as the donor and acceptor ligands, respectively. Single-crystal X-ray structures show linear molecular shape and coplanar arrangement of the donor and acceptor with small dihedral angles of <6.5°. The coplanar orientation and appropriate separation of the HOMO and LUMO in this type of molecules favour the formation of charge-transfer excited state with appreciable oscillator strength. Together with a minor but essential heavy atom effect of Au ion, the complexes in doped films exhibit highly efficient (Φ∼0.9) and short-lived (<1 μs) green emissions via TADF. Computational studies on this class of emitters have been performed to decipher the key reverse intersystem crossing (RISC) pathway. In addition to a small energy splitting between the lowest singlet and triplet excited states (ΔEST), the spin-orbit coupling (SOC) effect is found to be larger at a specific torsion angle between the donor and acceptor planes which favours the RISC process the most. This work provides an alternative molecular design to TADF Au(I) carbene emitters for OLED application. |
| Keywords: | gold complex high emission efficiency metal TADF nitrogen-heterocyclic carbene short lifetime |