Achieving small singlet–triplet energy gaps in polycyclic heteroaromatic emitters
Source abstract
Abstract
In polycyclic heteroaromatic (PHA) emitters, which possess great potential for application in ultrahigh-definition displays, the origin of a small singlet-triplet energy gap (ΔES1T1) and its relationship with the molecular structure still remain poorly established. Here we derive an effective expression for ΔES1T1, in which ΔES1T1 positively depends on 2KHL (where KHL is the exchange energy between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (LUMO)) and on the energy gap between LUMO and LUMO + 1 (ΔELUMO-LUMO+1). This expression for ΔES1T1 is validated over a series of 100 reported PHA emitters. It allows us to easily identify various molecular design approaches for managing ΔES1T1 by synergistically regulating 2KHL and ΔELUMO-LUMO+1. The proof-of-concept PHA molecules were synthesized and characterized to further confirm the validity of this expression for ΔES1T1. Overall, our work provides a physical picture to not only modulate ΔES1T1 in emerging PHA emitters but also design and screen such materials with small ΔES1T1.
Source: europepmc · Quality: candidate unverified · Source record ↗
Research context
OpenAlex topics: Organic Light-Emitting Diodes Research · Organic Electronics and Photovoltaics · Luminescence and Fluorescent Materials
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
References (41)
Show source-provided references
1. Berberan-Santos, M. N. & Garcia, J. M. M. Unusually strong delayed fluorescence of C70. J. Am. Chem. Soc. 118, 9391–9394 (1996).10.1021/ja961782s ↗
2. Endo, A. et al. Efficient up-conversion of triplet excitons into a singlet state and its application for organic light emitting diodes. Appl. Phys. Lett. 98, 083302 (2011).10.1063/1.3558906 ↗
3. Uoyama, H., Goushi, K., Shizu, K., Nomura, H. & Adachi, C. Highly efficient organic light-emitting diodes from delayed fluorescence. Nature 492, 234–238 (2012).10.1038/nature11687 ↗
4. Goushi, K., Yoshida, K., Sato, K. & Adachi, C. Organic light-emitting diodes employing efficient reverse intersystem crossing for triplet-to-singlet state conversion. Nat. Photon. 6, 253–258 (2012).10.1038/nphoton.2012.31 ↗
5. Tao, Y. et al. Thermally activated delayed fluorescence materials towards the breakthrough of organoelectronics. Adv. Mater. 26, 7931–7958 (2014).10.1002/adma.201402532 ↗
6. Yang, Z. et al. Recent advances in organic thermally activated delayed fluorescence materials. Chem. Soc. Rev. 46, 915–1016 (2017).10.1039/C6CS00368K ↗
7. Gan, L., Gao, K., Cai, X., Chen, D. & Su, S.-J. Achieving efficient triplet exciton utilization with large ΔEST and nonobvious delayed fluorescence by adjusting excited state energy levels. J. Phys. Chem. Lett. 9, 4725–4731 (2018).10.1021/acs.jpclett.8b01961 ↗
8. Hong, G. et al. A brief history of OLEDs—emitter development and industry milestones. Adv. Mater. 33, 2005630 (2021).10.1002/adma.202005630 ↗
9. de Silva, P., Kim, C. A., Zhu, T. & Voorhis, T. V. Extracting design principles for efficient thermally activated delayed fluorescence (TADF) from a simple four-state model. Chem. Mater. 31, 6995–7006 (2019).10.1021/acs.chemmater.9b01601 ↗
10. Yao, L., Yang, B. & Ma, Y. Progress in next-generation organic electroluminescent materials: material design beyond exciton statistics. Sci. China Chem. 57, 335–345 (2014).10.1007/s11426-013-5046-y ↗
11. Szabo, A. & Ostlund, N. S. Modern Quantum Chemistry: Introduction to Advanced Electronic Structure Theory (Courier Corporation, 2012).
12. Méhes, G., Nomura, H., Zhang, Q., Nakagawa, T. & Adachi, C. Enhanced electroluminescence efficiency in a spiro-acridine derivative through thermally activated delayed fluorescence. Angew. Chem. Int. Ed. 51, 11311–11315 (2012).10.1002/anie.201206289 ↗
13. Tanaka, H., Shizu, K., Miyazaki, H. & Adachi, C. Efficient green thermally activated delayed fluorescence (TADF) from a phenoxazine–triphenyltriazine (PXZ–TRZ) derivative. Chem. Comm. 48, 11392–11394 (2012).10.1039/c2cc36237f ↗
14. Hirata, S. et al. Highly efficient blue electroluminescence based on thermally activated delayed fluorescence. Nat. Mater. 14, 330–336 (2015).10.1038/nmat4154 ↗
15. Lin, T.-C. et al. Probe exciplex structure of highly efficient thermally activated delayed fluorescence organic light emitting diodes. Nat. Commun. 9, 3111 (2018).10.1038/s41467-018-05527-4 ↗
16. Wong, M. Y. & Zysman-Colman, E. Purely organic thermally activated delayed fluorescence materials for organic light-emitting diodes. Adv. Mater. 29, 1605444 (2017).10.1002/adma.201605444 ↗
17. Liu, Y., Li, C., Ren, Z., Yan, S. & Bryce, M. R. All-organic thermally activated delayed fluorescence materials for organic light-emitting diodes. Nat. Rev. Mater. 3, 18020 (2018).10.1038/natrevmats.2018.20 ↗
18. Xiao, L. et al. Recent progresses on materials for electrophosphorescent organic light-emitting devices. Adv. Mater. 23, 926–952 (2011).10.1002/adma.201003128 ↗
19. Ha, J. M., Hur, S. H., Pathak, A., Jeong, J.-E. & Woo, H. Y. Recent advances in organic luminescent materials with narrowband emission. NPG Asia Mater. 13, 53 (2021).10.1038/s41427-021-00318-8 ↗
20. Xu, Y., Xu, P., Hu, D. & Ma, Y. Recent progress in hot exciton materials for organic light-emitting diodes. Chem. Soc. Rev. 50, 1030–1069 (2021).10.1039/D0CS00391C ↗
21. Hatakeyama, T. et al. Ultrapure blue thermally activated delayed fluorescence molecules: efficient HOMO–LUMO separation by the multiple resonance effect. Adv. Mater. 28, 2777–2781 (2016).10.1002/adma.201505491 ↗
22. Nakatsuka, S., Gotoh, H., Kinoshita, K., Yasuda, N. & Hatakeyama, T. Divergent synthesis of heteroatom-centered 4,8,12-triazatriangulenes. Angew. Chem. Int. Ed. 56, 5087–5090 (2017).10.1002/anie.201701246 ↗
23. Yang, Y. et al. Chiral multi-resonance TADF emitters exhibiting narrowband circularly polarized electroluminescence with an EQE of 37.2%. Angew. Chem. Int. Ed. 61, e202202227 (2022).10.1002/anie.202202227 ↗
24. Oda, S., Kawakami, B., Kawasumi, R., Okita, R. & Hatakeyama, T. Multiple resonance effect-induced sky-blue thermally activated delayed fluorescence with a narrow emission band. Org. Lett. 21, 9311–9314 (2019).10.1021/acs.orglett.9b03342 ↗
25. Han, S. H., Jeong, J. H., Yoo, J. W. & Lee, J. Y. Ideal blue thermally activated delayed fluorescence emission assisted by a thermally activated delayed fluorescence assistant dopant through a fast reverse intersystem crossing mediated cascade energy transfer process. J. Mater. Chem. C 7, 3082–3089 (2019).10.1039/C8TC06575F ↗
26. Zou, Y. et al. High-performance narrowband pure-red OLEDs with external quantum efficiencies up to 36.1% and ultralow efficiency roll-off. Adv. Mater. 34, 2201442 (2022).10.1002/adma.202201442 ↗
27. Fan, X.-C. et al. Ultrapure green organic light-emitting diodes based on highly distorted fused π-conjugated molecular design. Nat. Photon. 17, 280–285 (2023).10.1038/s41566-022-01106-8 ↗
28. Kondo, Y. et al. Narrowband deep-blue organic light-emitting diode featuring an organoboron-based emitter. Nat. Photon. 13, 678–682 (2019).10.1038/s41566-019-0476-5 ↗
29. Hall, D. et al. Improving processability and efficiency of resonant TADF emitters: a design strategy. Adv. Opt. Mater. 8, 1901627 (2020).10.1002/adom.201901627 ↗
30. Pershin, A. et al. Highly emissive excitons with reduced exchange energy in thermally activated delayed fluorescent molecules. Nat. Commun. 10, 597 (2019).10.1038/s41467-019-08495-5 ↗
31. Hall, D. et al. Modeling of multiresonant thermally activated delayed fluorescence emitters—properly accounting for electron correlation is key! J. Chem. Theory Comput. 18, 4903–4918 (2022).10.1021/acs.jctc.2c00141 ↗
32. Sanz-Rodrigo, J., Olivier, Y. & Sancho-García, J.-C. Computational studies of molecular materials for unconventional energy conversion: the challenge of light emission by thermally activated delayed fluorescence. Molecules 25, 1006 (2020).10.3390/molecules25041006 ↗
33. Ricci, G., San-Fabián, E., Olivier, Y. & Sancho-García, J. C. Singlet-triplet excited-state inversion in heptazine and related molecules: assessment of TD-DFT and ab initio methods. ChemPhysChem 22, 553–560 (2021).10.1002/cphc.202000926 ↗
34. Shizu, K. & Kaji, H. Comprehensive understanding of multiple resonance thermally activated delayed fluorescence through quantum chemistry calculations. Commun. Chem. 5, 53 (2022).10.1038/s42004-022-00668-6 ↗
35. Pratik, S. M., Coropceanu, V. & Brédas, J.-L. Enhancement of thermally activated delayed fluorescence (TADF) in multi-resonant emitters via control of chalcogen atom embedding. Chem. Mater. 34, 8022–8030 (2022).10.1021/acs.chemmater.2c01952 ↗
36. Pratik, S. M., Coropceanu, V. & Brédas, J.-L. Purely organic emitters for multiresonant thermally activated delay fluorescence: design of highly efficient sulfur and selenium derivatives. ACS Mater. Lett. 4, 440–447 (2022).10.1021/acsmaterialslett.1c00809 ↗
37. Sun, H., Zhong, C. & Brédas, J.-L. Reliable prediction with tuned range-separated functionals of the singlet–triplet gap in organic emitters for thermally activated delayed fluorescence. J. Chem. Theory Comput. 11, 3851–3858 (2015).10.1021/acs.jctc.5b00431 ↗
38. Frisch, M. et al. Gaussian (Gaussian, 2016).
39. Neese, F., Wennmohs, F., Becker, U. & Riplinger, C. The ORCA quantum chemistry program package. J. Chem. Phys. 152, 224108 (2020).10.1063/5.0004608 ↗
40. Weigend, F. & Ahlrichs, R. Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: design and assessment of accuracy. Phys. Chem. Chem. Phys. 7, 3297–3305 (2005).10.1039/b508541a ↗
41. Sun, Q. et al. PySCF: the Python-based simulations of chemistry framework. WIREs Comput. Mol. Sci. 8, e1340 2018).10.1002/wcms.1340 ↗