Construction of Blue Thermally Activated Delayed Fluorescence Materials Based on the Heptagonal Triarylamine Donor

doi:10.6023/cjoc202312006

Abstract

The development of efficient blue light-emitting materials is a crucial yet challenging task in organic light-emitting diodes (OLED). Two novel blue light-emitting molecules, TRZCz-TPA and TRZ-TPA, have been designed and synthesized based on the heptagonal 9H-tripheno[b,d,f]nitrozoafluorene (TPA) donor. Their thermal stability, electrochemical properties, photophysical properties, and device performances were characterized. TRZCz-TPA and TRZ-TPA both exhibit blue emission in toluene solution with emission peaks at 455 and 440 nm, respectively. In contrast to TRZ-TPA, which exhibits through-bond charge transfer (TBCT) from the TPA donor to the diphenyltriazine (TRZ) acceptor, TRZCz-TPA, featuring two adjacent 3,6-di-tert-butylcarbazole (tBuCz) donors near the TRZ acceptor, demonstrates through-space charge transfer (TSCT) from the tBuCz donors to the TRZ acceptor. This leads to a remarkable reduction in the singlet-triplet energy gap (ΔE_ST) from 0.53 eV to 0.04 eV, thereby displaying thermally activated delayed fluorescence (TADF) properties. Additionally, tBuCz donor with large steric hindrance effectively suppresses aggregation-induced quenching in the aggregated state. Consequently, TRZCz-TPA achieves a photoluminescence quantum yield (PLQY) of 42.0% and a maximum external quantum efficiency (EQE_max) of 10.4% in OLED devices, significantly outperforming TRZ-TPA (PLQY=6.5%, EQE_max=3.7%).

Key words: organic light-emitting diodes, thermally activated delayed fluorescence, through-bond charge transfer, through- space charge transfer, heptagonal triarylamine donor

Cite this article

Zhi Li, Zhenlong Li, Junjie Liu, Weiguo Han, Jingsong You, Zhengyang Bin. Construction of Blue Thermally Activated Delayed Fluorescence Materials Based on the Heptagonal Triarylamine Donor[J]. Chinese Journal of Organic Chemistry, 2024, 44(6): 2006-2013.

Export EndNote|Reference Manager|ProCite|BibTeX|RefWorks

share this article

Fig. & Tab. 5

Scheme 1. Synthetic routes to the target molecules

Compd.	HOMO/ eV	LUMO^c/ eV	λ_abs^a/ nm	λ_em^a/ nm	FWHM^a/ nm	ΔE_ST^a/ eV	τ_p^b/ ns	τ_d^b/ μs	PLQY^b/ %	C₁^b/ %	C₂^b/ %	k_RISC^b/ 10⁶ s^–1	T_d/ ℃	T_m/ ℃
TRZCz-TPA	–5.52	–2.11	321	455	68	0.04	8.49	1.41	42.0	30.5	69.5	1.9	452	319
TRZ-TPA	–5.61	–2.45	363	440	80	0.53	3.09	—	6.5	—	—	—	415	307

Table 1. Photophysical and thermal parameters of TRZCz-TPA and TRZ-TPA

Figure1. Molecular structures and frontline molecular orbital distributions of TRZCz-TPA and TRZ-TPA

Figure 2. UV spectra, room-temperature fluorescence spectra (298 K) and low-temperature phosphorescence spectra (77 K) of (a) TRZCz-TPA and (b) TRZ-TPA in toluene solution; (c) room-temperature fluorescence spectra of the doped films (40% TRZCz-TPA or TRZ-TPA:DPEPO, 298 K); (d) transient photoluminescence spectra of the doped films (40% TRZCz-TPA or TRZ-TPA:DPEPO, 298 K)

Figure 3. (a) Molecular structures of the materials used OLED devices; (b) OLED device structure; (c) eletroluminescence spectra of OLED devices; (d) EQE-luminance curves and (e) current density-voltage-luminance curves of OLED devices

References 32

[1]	Adachi, C. Jpn. J. Appl. Phys. 2014, 53, 060101.
[2]	Chaskar, A.; Chen, H.-F.; Wong, K.-T. Adv. Mater. 2011, 23, 3876.
[3]	Wong, M. Y.; Zysman-Colman, E. Adv. Mater. 2017, 29, 1605444.
[4]	Wu, Y.; Zhang, Z.; Yue, S.; Huang, R.; Du, H.; Zhao, Y. Chin. J. Chem. 2015, 33, 897.
[5]	Li, B. Chin. J. Org. Chem. 2015, 35, 2487. (in Chinese)
	(李保林, 有机化学, 2015, 35, 2487.)
[6]	Tao, Y.; Yuan, K.; Chen, T.; Xu, P.; Li, H.; Chen, R.; Zheng, C.; Zhang, L.; Huang, W. Adv. Mater. 2014, 26, 7931.
[7]	Yang, X.; Jiao, B.; Dang, J.-S.; Sun, Y.; Wu, Y.; Zhou, G.; Wong, W.-Y. ACS Appl. Mater. Interfaces 2018, 10, 10227.
[8]	Baldo, M. A.; O'Brien, D. F.; You, Y.; Shoustikov, A.; Sibley, S.; Thompson, M. E.; Forrest, S. R. Nature 1998, 395, 151.
[9]	Huang, C.; Qiu, Z.; Gao, Y.; Chen, W.; Ji, S.; Huo, Y. Chin. J. Org. Chem. 2021, 41, 3050. (in Chinese)
	(黄酬, 邱志鹏, 高杨, 陈文铖, 籍少敏, 霍延平, 有机化学, 2021, 41, 3050).
[10]	Park, Y.-S.; Lee, S.; Kim, K.-H.; Kim, S.-Y.; Lee, J.-H.; Kim, J.-J. Adv. Funct. Mater. 2013, 23, 4914.
[11]	Wang, Q.; Oswald, I. W. H.; Yang, X.; Zhou, G.; Jia, H.; Qiao, Q.; Chen, Y.; Hoshikawa-Halbert, J.; Gnade, B. E. Adv. Mater. 2014, 26, 8107.
[12]	Goushi, K.; Yoshida, K.; Sato, K.; Adachi, C. Nat. Photonics 2012, 6, 253.
[13]	Wang, T; Hua, X; Yu, Y; Yuan, Y; Feng, M; Jiang, Z. Chin. J. Org. Chem. 2019, 39, 1436. (in Chinese)
	(王彤彤, 华晓晨, 郁友军, 袁熠, 冯敏强, 蒋佐权, 有机化学, 2019, 39, 1436).
[14]	Endo, A.; Sato, K.; Yoshimura, K.; Kai, T.; Kawada, A.; Miyazaki, H.; Adachi, C. Appl. Phys. Lett. 2011, 98, 083302.
[15]	Huang, Z.; Yang, D.; Ma, D.; Bin, Z.; You, J. Sci. China Chem. 2024, 67, 1181.
[16]	Shi, Q; Wang, L. Chin. J. Org. Chem. 2022, 42, 1256. (in Chinese)
	(石强, 王乐勇, 有机化学, 2022, 42, 1256.)
[17]	Guo, J.; Zhao, Z.; Tang, B. Z. Adv. Opt. Mater. 2018, 6, 1800264.
[18]	Sagara, Y.; Shizu, K.; Tanaka, H.; Miyazaki, H.; Goushi, K.; Kaji, H.; Adachi, C. Chem. Lett. 2014, 44, 360.
[19]	Dias, F. B.; Bourdakos, K. N.; Jankus, V.; Moss, K. C.; Kamtekar, K. T.; Bhalla, V.; Santos, J.; Bryce, M. R.; Monkman, A. P. Adv. Mater. 2013, 25, 3707.
[20]	Lee, D. R.; Kim, M.; Jeon, S. K.; Hwang, S.-H.; Lee, C. W.; Lee, J. Y. Adv. Mater. 2015, 27, 5861.
[21]	Méhes, G.; Nomura, H.; Zhang, Q.; Nakagawa, T.; Adachi, C. Angew. Chem., Int. Ed. 2012, 51, 11311.
[22]	Liu, Y.; Xiao, X.; Huang, Z.; Yang, D.; Ma, D.; Liu, J.; Lei, B.; Bin, Z.; You, J. Angew. Chem., Int. Ed. 2022, 61, e202210210.
[23]	Liang, W.; Yang, Y.; Yang, M.; Zhang, M.; Li, C.; Ran, Y.; Lan, J.; Bin, Z.; You, J. Angew. Chem., Int. Ed. 2021, 60, 3493.
[24]	Liu, J.; Bin, Z.; Yang, D.; Ma, D.; You, J. Chem. Eng. J. 2023, 466, 142910.
[25]	Ma, W.; Bin, Z.; Yang, G.; Liu, J.; You, J. Angew. Chem., Int. Ed. 2022, 61, e202116681.
[26]	Huang, Z.; Bin, Z.; Su, R.; Yang, F.; Lan, J.; You, J. Angew. Chem., Int. Ed. 2020, 59, 9992.
[27]	Huang, Z.; Lei, B.; Yang, D.; Ma, D.; Bin, Z.; You, J. Angew. Chem., Int. Ed. 2022, 61, e202213157.
[28]	Xiao, X.; Lei, B.; Wu, D.; Bin, Z. Chem. Commun. 2023, 59, 6556.
[29]	Yang, S; Wang, Y; Peng, C; Wu, Z; Yuan, S; Yu, Y; Li, H; Wang, T; Li, H; Zheng, Y; Jiang, Z; Liao, L. J. Am. Chem. Soc. 2020, 142, 17756.
[30]	Zhao, Z.; Zeng, C.; Peng, X.; Liu, Y.; Zhao, H.; Hua, L.; Su, S.; Yan, S.; Ren, Z. Angew. Chem., Int. Ed. 2022, 61, e202210864.
[31]	Han, W.; Liu, J.; Ran, C.; Huang, Z.; Gao, G.; You, J.; Bin, Z. Angew. Chem., Int. Ed. 2023, e202312297.
[32]	Wang, X.; Xu, Y.; Yang, L.; Lu, X.; Zou, H.; Yang, W.; Zhang, Y.; Li, Z.; Ma, M. J. Fluoresc. 2018, 28, 707.

基于七元环三芳胺给体的蓝光热活化延迟荧光材料的构筑