Peripheral carbazole units-decorated MR emitter containing B−N covalent bond for highly efficient green OLEDs with low roll-off

Danrui Wan; Jianping Zhou; Guoyun Meng; Ning Su; Dongdong Zhang; Lian Duan; Junqiao Ding

doi:10.1088/1674-4926/24040008

J. Semicond. > 2024, Volume 45 > Issue 8 > 082402

ARTICLES

Peripheral carbazole units-decorated MR emitter containing B−N covalent bond for highly efficient green OLEDs with low roll-off

Danrui Wan^{1, 3}, Jianping Zhou², Guoyun Meng^1,, Ning Su¹, Dongdong Zhang², Lian Duan² and Junqiao Ding^{1, 3,}

+ Author Affiliations

1. School of Chemical Science and Technology, Yunnan University, Kunming 650091, China
2. Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084, China
3. Southwest United Graduate School, Kunming 650092, China

Author Bio:

Danrui Wan got her BS degree from Xiamen University in 2017. Now she is pursuing a master’s degree at Yunnan University and Southwest United Graduate School under the supervision of Prof. Junqiao Ding. Her research focuses on boron−nitrogen covalent bonds doped multi-resonance (MR) materials.

Guoyun Meng obtained his Ph.D. degree in 2020 from Beijing Institute of Technology. From 2020 to 2022, he conducted postdoctoral research at Tsinghua University. Presently, he serves as an associate professor at the School of Chemical Science and Technology, Yunnan University. His research focuses on boron nitrogen-embedded polycyclic aromatic multiple resonance emitters and devices.

Junqiao Ding received his BS from Wuhan University of Technology in 1999 and gained his PhD from Changchun Institute of Applied Chemistry (CAS) in 2007. After graduation, he joined the same institute as a research fellow and later was promoted to a professor in 2014. During 2010−2011, he performed postdoctoral work at the University of New Mexico. Since 2020, he has been working as a professor at School of Chemical Science and Technology, Yunnan University. His research focuses on organic/polymeric optoelectronic materials and devices.

Corresponding author: Guoyun Meng, mengguoyun@ynu.edu.cn; Junqiao Ding, dingjunqiao@ynu.edu.cn

DOI: 10.1088/1674-4926/24040008

Abstract: Boron−nitrogen doped multiple resonance (BN-MR) emitters, characterized by B−N covalent bonds, offer distinctive advantages as pivotal building blocks for facile access to novel MR emitters featuring narrowband spectra and high efficiency. However, there remains a scarcity of exploration concerning synthetic methods and structural derivations to expand the library of novel BN-MR emitters. Herein, we present the synthesis of a BN-MR emitter, tCz[B−N]N, through a one-pot borylation reaction directed by the amine group, achieving an impressive yield of 94%. The emitter is decorated by incorporating two 3,6-di-t-butylcarbazole (tCz) units into a B−N covalent bond doped BN-MR parent molecule via para-C−π−D and para-N−π−D conjugations. This peripheral decoration strategy enhances the reverse intersystem crossing process and shifts the emission band towards the pure green region, peaking at 526 nm with a narrowband full-width at half maximum (FWHM) of 41 nm. Consequently, organic light emitting diodes (OLEDs) employing this emitter achieved a maximum external quantum efficiency (EQE_max) value of 27.7%, with minimal efficiency roll-off. Even at a practical luminance of 1000 cd∙m⁻², the device maintains a high EQE value of 24.6%.

Key words: multi-resonance, narrowband emission, B−N covalent bond, organic light emitting diodes

References

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Fig. 1. (Color online) Depicts the chemical structures and design strategies of the previously reported BN-MR emitters, namely BCz-BN and BBCz-Y, and the B−N bond embedded MR emitter, [B−N]N. This work illustrates the peripheral decoration strategy employed to modify the excited-state characteristics of the B−N bond-embedded MR emitter by introducing donor groups.

DownLoad: Full-Size Img PowerPoint

Fig. 2. (Color online) The synthetic route of compound tCz[B−N]N.

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Fig. 3. (Color online) (a) Displays the thermal stability of tCz[B−N]N. (b) CV and DPV curves (vs. Fc/Fc⁺) were recorded in degassed and dry CH₂Cl₂ solution with 0.1 M n-Bu₄NPF₆ as the electrolyte.

DownLoad: Full-Size Img PowerPoint

Fig. 4. (Color online) The distribution of the HOMO and LUMO for tCz[B−N]N, along with the representation of hole (blue) and electron (green) isosurface for S₁ state, and the RMSD between S₀ (red) and S₁ (blue) states, the dipole moment of S₁ geometry (red arrow indicates vector scale), oscillator strengths (f).

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Fig. 5. (Color online) (a) Absorption and PL spectra of tCz[B−N]N measured in toluene solution. (b) Solvent polarity-dependent PL spectra range from hexane to methanol. (c) Fluorescence and phosphorescence (20 ms delayed) spectra of tCz[B−N]N recorded in toluene at 77 K. The S₁ and T₁ energy was estimated from the onsets of the fluorescent and phosphorescent spectra, respectively. (d) PL transient decay curves of tCz[B−N]N in the doped film.

DownLoad: Full-Size Img PowerPoint

Fig. 6. (Color online) (a) Illustrates the architecture of the OLED devices and (b) structures of each layer’s functional materials. (c) The luminance-voltage−current density plots for the device. (d) EL spectra of 1.0 wt.% doped device and (e) CIE coordinates of the corresponding device at 1000 cd∙cm⁻² (the photograph presents the EL color of the device). (f) The EL spectra under different brightness. (g) The plots of CE and PE versus luminance. (h) The plots of EQE versus luminance at different doping concentrations.

DownLoad: Full-Size Img PowerPoint

Table 1. Photophysical properties of tCz[B−N]N and the reference molecule BBCz-Y.

Compound	λ_abs (nm)^a)	λ_PL (nm)^b)	FWHM (nm)^b)	Φ_PL (%)^c)	Φ_PF (%)^d)	Φ_DF (%)^d)	E_ST (eV)^e)	τ_PF (ns)^f)	τ_DF (μs)^f)	k_r (10⁷ s⁻¹)^g)	k_ISC (10⁷ s⁻¹)^g)	k_RISC (10⁵ s⁻¹)^g)	HOMO/ LUMO (eV)^h)
BBCz-Y	505	549/549	42/48	85	26	59	0.14	5.6	29.0	4.7	13.0	1.0	−5.15/ −2.72
tCz[B−N]N	499	526/533	41/45	93	32	61	0.18	5.0	19.2	6.34	13.66	1.47	−5.24/ −2.60
^a)Maximum absorption wavelength measured in toluene (10⁻⁵ M); ^b)maximum emission wavelength and the FWHM recorded in toluene (10⁻⁵ M) and doped film; ^c)absolute PL quantum yield evaluated using an integrating sphere in the doped film; ^d)fractional quantum yields for prompt (Φ_PF) and delayed fluorescence (Φ_DF); ^e)singlet−triplet energy gap; ^f)emission lifetime for prompt (τ_PF) and delayed (τ_DF) fluorescence; ^g)rate constant of fluorescence radiative decay (k_r), intersystem crossing (k_ISC) and reverse intersystem crossing (k_RISC); ^h)HOMO and LUMO determined from cyclic voltammetry.

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Table 2. A summary of the OLED performance based on tCz[B−N]N.

tCz[B−N]N x (wt.%)	λ_EL^a) (nm)	FWHM^b) (nm/eV)	V_on^c) (V)	L_max^d) (cd∙m⁻²)	EQE_{max/1000/5000}^e) (%)	PE_max^e) (lm∙W⁻¹)	CE_max^e) (cd∙A⁻¹)	CIE (x, y)^f)
1.0	532	49/0.21	2.8	59620	27.7/24.6/15.0	96.8	104.7	(0.287, 0.631)
2.0	535	49/0.21	2.9	39800	26.8/23.2/11.4	99.4	105.5	(0.311, 0.639)
3.0	535	49/0.21	2.9	34470	25.8/22.2/10.8	95.6	103.5	(0.313, 0.641)
^a)EL peak wavelength at 1000 cd∙cm⁻²; ^b)FWHM of the EL spectrum; ^c)turn-on voltage (V_on), recorded at 1.0 cd∙cm⁻²; ^d)maximum luminance (L_max); ^e)maximum EQE, and values recorded at 1000 and 5000 cd∙cm⁻², maximum power efficiency (PE_max) and current efficiency (CE_max);^f)CIE coordinates at 1000 cd∙cm⁻².

DownLoad: CSV

[1]	Hatakeyama T, Shiren K, Nakajima K, et al. Ultrapure blue thermally activated delayed fluorescence molecules: Efficient HOMO-LUMO separation by the multiple resonance effect. Adv Mater, 2016, 28, 2777 doi: 10.1002/adma.201505491
[2]	Mamada M, Hayakawa M, Ochi J, et al. Organoboron-based multiple-resonance emitters: Synthesis, structure–property correlations, and prospects. Chem Soc Rev, 2024, 53, 1624 doi: 10.1039/D3CS00837A
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[4]	Madayanad Suresh S, Hall D, Beljonne D, et al. Multiresonant thermally activated delayed fluorescence emitters based on heteroatom-doped nanographenes: Recent advances and prospects for organic light-emitting diodes. Adv Funct Mater, 2020, 30, 1908677 doi: 10.1002/adfm.201908677
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[6]	Chen C, Du C Z, Wang X Y. The rise of 1, 4-BN-heteroarenes: Synthesis, properties, and applications. Adv Sci, 2022, 9, 2200707 doi: 10.1002/advs.202200707
[7]	Yu Y J, Liu F M, Meng X Y, et al. Carbonyl-containing thermally activated delayed fluorescence emitters for narrow-band electroluminescence. Chem Eur J, 2023, 29, e202202628 doi: 10.1002/chem.202202628
[8]	Kang J, Jeon S O, Kim I, et al. Color stable deep blue multi-resonance organic emitters with narrow emission and high efficiency. Adv Sci, 2023, 10, 2302619 doi: 10.1002/advs.202302619
[9]	Wei J B, Zhang C, Zhang D D, et al. Indolo[3, 2, 1-jk]carbazole embedded multiple-resonance fluorophors for narrowband deep-blue electroluminescence with EQE ≈ 34.7 % and CIE_y ≈ 0.085. Angew Chem Int Ed, 2021, 60, 12269 doi: 10.1002/anie.202017328
[10]	Hirai H, Nakajima K, Nakatsuka S, et al. One-step borylation of 1, 3-diaryloxybenzenes towards efficient materials for organic light-emitting diodes. Angew Chem Int Ed, 2015, 54, 13581 doi: 10.1002/anie.201506335
[11]	Kondo Y, Yoshiura K, Kitera S, et al. Narrowband deep-blue organic light-emitting diode featuring an organoboron-based emitter. Nat Photonics, 2019, 13, 678 doi: 10.1038/s41566-019-0476-5
[12]	Yang M L, Park I S, Yasuda T. Full-color, narrowband, and high-efficiency electroluminescence from boron and carbazole embedded polycyclic heteroaromatics. J Am Chem Soc, 2020, 142, 19468 doi: 10.1021/jacs.0c10081
[13]	Liu Y, Xiao X, Ran Y, et al. Molecular design of thermally activated delayed fluorescent emitters for narrowband orange-red OLEDs boosted by a cyano-functionalization strategy. Chem Sci, 2021, 12, 9408 doi: 10.1039/D1SC02042K
[14]	Zhang Y W, Zhang D D, Huang T Y, et al. Multi-resonance deep-red emitters with shallow potential-energy surfaces to surpass energy-gap law. Angew Chem Int Ed, 2021, 60, 20498 doi: 10.1002/anie.202107848
[15]	Park I S, Min H, Yasuda T. Ultrafast triplet–singlet exciton interconversion in narrowband blue organoboron emitters doped with heavy chalcogens. Angew Chem Int Ed, 2022, 61, e202205684 doi: 10.1002/anie.202205684
[16]	Xu Y C, Wang Q Y, Cai X L, et al. Frontier molecular orbital engineering: Constructing highly efficient narrowband organic electroluminescent materials. Angew Chem Int Ed, 2023, 62, e202312451 doi: 10.1002/anie.202312451
[17]	Hu Y X, Miao J S, Hua T, et al. Efficient selenium-integrated TADF OLEDs with reduced roll-off. Nat Photonics, 2022, 16, 803 doi: 10.1038/s41566-022-01083-y
[18]	Wu X G, Huang J W, Su B K, et al. Fabrication of circularly polarized MR-TADF emitters with asymmetrical peripheral-lock enhancing helical B/N-doped nanographenes. Adv Mater, 2022, 34, e2105080 doi: 10.1002/adma.202105080
[19]	Luo X F, Zhang L X, Zheng Y X, et al. Improving reverse intersystem crossing of MR-TADF emitters for OLEDs. J Semicond, 2022, 43, 110202 doi: 10.1088/1674-4926/43/11/110202
[20]	Zhang Y W, Zhang D D, Wei J B, et al. Multi-resonance induced thermally activated delayed fluorophores for narrowband green OLEDs. Angew Chem Int Ed, 2019, 58, 16912 doi: 10.1002/anie.201911266
[21]	Xu Y C, Cheng Z, Li Z Q, et al. Molecular-structure and device-configuration optimizations toward highly efficient green electroluminescence with narrowband emission and high color purity. Adv Opt Mater, 2020, 8, 1902142 doi: 10.1002/adom.201902142
[22]	Xu Y C, Li C L, Li Z Q, et al. Constructing charge-transfer excited states based on frontier molecular orbital engineering: Narrowband green electroluminescence with high color purity and efficiency. Angew Chem Int Ed, 2020, 59, 17442 doi: 10.1002/anie.202007210
[23]	Knöller J A, Meng G Y, Wang X, et al. Intramolecular borylation via sequential B-mes bond cleavage for the divergent synthesis of B, N, B-doped benzo[4]helicenes. Angew Chem Int Ed, 2020, 59, 3156 doi: 10.1002/anie.201912340
[24]	Matsui K, Oda S, Yoshiura K, et al. One-shot multiple borylation toward BN-doped nanographenes. J Am Chem Soc, 2018, 140, 1195 doi: 10.1021/jacs.7b10578
[25]	Lv X L, Miao J S, Liu M H, et al. Extending the π-skeleton of multi-resonance TADF materials towards high-efficiency narrowband deep-blue emission. Angew Chem Int Ed, 2022, 61, e202201588 doi: 10.1002/anie.202201588
[26]	Wu L, Huang Z Y, Miao J S, et al. Orienting group directed cascade borylation for efficient one-shot synthesis of 1, 4-BN-doped polycyclic aromatic hydrocarbons as narrowband organic emitters. Angew Chem Int Ed, 2024, 63, e202402020 doi: 10.1002/anie.202402020
[27]	Fan X C, Huang F, Wu H, et al. A quadruple-borylated multiple-resonance emitter with para/meta heteroatomic patterns for narrowband orange-red emission. Angew Chem Int Ed, 2023, 62, e202305580 doi: 10.1002/anie.202305580
[28]	Meng G Y, Dai H Y, Huang T Y, et al. Amine-directed formation of B‒N bonds for BN-fused polycyclic aromatic multiple resonance emitters with narrowband emission. Angew Chem Int Ed, 2022, 61, e202207293 doi: 10.1002/anie.202207293
[29]	Meng G Y, Dai H Y, Zhou J P, et al. Wide-range color-tunable polycyclo-heteraborin multi-resonance emitters containing B-N covalent bonds. Chem Sci, 2023, 14, 979 doi: 10.1039/D2SC06343C
[30]	Meng G Y, Zhou J P, Han X S, et al. B‒N covalent bond embedded double hetero-[n]helicenes for pure red narrowband circularly polarized electroluminescence with high efficiency and stability. Adv Mater, 2024, 36, 2307420 doi: 10.1002/adma.202307420
[31]	Meng G Y, Zhou J P, Huang T Y, et al. B‒N/B‒O contained heterocycles as fusion locker in multi-resonance frameworks towards highly-efficient and stable ultra-narrowband emission. Angew Chem Int Ed, 2023, 62, e202309923 doi: 10.1002/anie.202309923
[32]	Tam B S T, Dong S C, Tang C W. Low-temperature conformal vacuum deposition of OLED devices using close-space sublimation. J Semicond, 2023, 44, 092602 doi: 10.1088/1674-4926/44/9/092602
[33]	Lu T, Chen F W. Multiwfn: A multifunctional wavefunction analyzer. J Comput Chem, 2012, 33, 580 doi: 10.1002/jcc.22885
[34]	Liu Z Y, Lu T, Chen Q X. An sp-hybridized all-carboatomic ring, cyclo[18]carbon: Electronic structure, electronic spectrum, and optical nonlinearity. Carbon, 2020, 165, 461 doi: 10.1016/j.carbon.2020.05.023
[35]	Meng G Y, Dai H Y, Wang Q, et al. High-efficiency and stable short-delayed fluorescence emitters with hybrid long- and short-range charge-transfer excitations. Nat Commun, 2023, 14, 2394 doi: 10.1038/s41467-023-38086-4
[36]	Ren B Y, Zuo C T, Sun Y G, et al. Intramolecular spatial charge transfer enhances TADF efficiency. J Semicond, 2021, 42, 050201 doi: 10.1088/1674-4926/42/5/050201
[37]	He X, Lou J L, Li B X, et al. Rational medium-range charge transfer strategy toward highly efficient violet-blue organic light-emitting diodes with narrowed emission. Adv Mater, 2024, 36, 2310417 doi: 10.1002/adma.202310417
[38]	Wei P C, Zhang D D, Duan L. Modulation of Förster and dexter interactions in single-emissive-layer all-fluorescent WOLEDs for improved efficiency and extended lifetime. Adv Funct Mater, 2020, 30, 1907083 doi: 10.1002/adfm.201907083
[39]	Huang T Y, Wang Q, Xiao S, et al. Simultaneously enhanced reverse intersystem crossing and radiative decay in thermally activated delayed fluorophors with multiple through-space charge transfers. Angew Chem Int Ed, 2021, 60, 23771 doi: 10.1002/anie.202109041
[40]	Jeon S O, Lee K H, Kim J S, et al. High-efficiency, long-lifetime deep-blue organic light-emitting diodes. Nat Photonics, 2021, 15, 208 doi: 10.1038/s41566-021-00763-5
[41]	Chan C Y, Tanaka M, Lee Y T, et al. Stable pure-blue hyperfluorescence organic light-emitting diodes with high-efficiency and narrow emission. Nat Photonics, 2021, 15, 203 doi: 10.1038/s41566-020-00745-z
[42]	Zhang Y W, Wei J B, Zhang D D, et al. Sterically wrapped multiple resonance fluorophors for suppression of concentration quenching and spectrum broadening. Angew Chem Int Ed, 2022, 61, e202113206 doi: 10.1002/anie.202113206
[43]	Jiang P C, Miao J S, Cao X S, et al. Quenching-resistant multiresonance TADF emitter realizes 40% external quantum efficiency in narrowband electroluminescence at high doping level. Adv Mater, 2022, 34, e2106954 doi: 10.1002/adma.202106954

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Received: 08 April 2024 Revised: 28 April 2024 Online: Accepted Manuscript: 17 May 2024Uncorrected proof: 20 May 2024Published: 15 August 2024

Article Navigation > Journal of Semiconductors > 2024 > 45(8): 082402

Danrui Wan, Jianping Zhou, Guoyun Meng, Ning Su, Dongdong Zhang, Lian Duan, Junqiao Ding. Peripheral carbazole units-decorated MR emitter containing B−N covalent bond for highly efficient green OLEDs with low roll-off[J]. Journal of Semiconductors, 2024, 45(8): 082402. doi: 10.1088/1674-4926/24040008 ****D R Wan, J P Zhou, G Y Meng, N Su, D D Zhang, L Duan, and J Q Ding, Peripheral carbazole units-decorated MR emitter containing B−N covalent bond for highly efficient green OLEDs with low roll-off[J]. J. Semicond., 2024, 45(8), 082402 doi: 10.1088/1674-4926/24040008

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D R Wan, J P Zhou, G Y Meng, N Su, D D Zhang, L Duan, and J Q Ding, Peripheral carbazole units-decorated MR emitter containing B−N covalent bond for highly efficient green OLEDs with low roll-off[J]. J. Semicond., 2024, 45(8), 082402 doi: 10.1088/1674-4926/24040008

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Peripheral carbazole units-decorated MR emitter containing B−N covalent bond for highly efficient green OLEDs with low roll-off

DOI: 10.1088/1674-4926/24040008

1.
School of Chemical Science and Technology, Yunnan University, Kunming 650091, China
2.
Key Laboratory of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing 100084, China
3.
Southwest United Graduate School, Kunming 650092, China

More Information

Danrui Wan got her BS degree from Xiamen University in 2017. Now she is pursuing a master’s degree at Yunnan University and Southwest United Graduate School under the supervision of Prof. Junqiao Ding. Her research focuses on boron−nitrogen covalent bonds doped multi-resonance (MR) materials
Guoyun Meng obtained his Ph.D. degree in 2020 from Beijing Institute of Technology. From 2020 to 2022, he conducted postdoctoral research at Tsinghua University. Presently, he serves as an associate professor at the School of Chemical Science and Technology, Yunnan University. His research focuses on boron nitrogen-embedded polycyclic aromatic multiple resonance emitters and devices
Junqiao Ding received his BS from Wuhan University of Technology in 1999 and gained his PhD from Changchun Institute of Applied Chemistry (CAS) in 2007. After graduation, he joined the same institute as a research fellow and later was promoted to a professor in 2014. During 2010−2011, he performed postdoctoral work at the University of New Mexico. Since 2020, he has been working as a professor at School of Chemical Science and Technology, Yunnan University. His research focuses on organic/polymeric optoelectronic materials and devices
Corresponding author: mengguoyun@ynu.edu.cn; dingjunqiao@ynu.edu.cn
Received Date: 2024-04-08
Revised Date: 2024-04-28

Available Online: 2024-05-17

Abstract

Abstract

Boron−nitrogen doped multiple resonance (BN-MR) emitters, characterized by B−N covalent bonds, offer distinctive advantages as pivotal building blocks for facile access to novel MR emitters featuring narrowband spectra and high efficiency. However, there remains a scarcity of exploration concerning synthetic methods and structural derivations to expand the library of novel BN-MR emitters. Herein, we present the synthesis of a BN-MR emitter, tCz[B−N]N, through a one-pot borylation reaction directed by the amine group, achieving an impressive yield of 94%. The emitter is decorated by incorporating two 3,6-di-t-butylcarbazole (tCz) units into a B−N covalent bond doped BN-MR parent molecule via para-C−π−D and para-N−π−D conjugations. This peripheral decoration strategy enhances the reverse intersystem crossing process and shifts the emission band towards the pure green region, peaking at 526 nm with a narrowband full-width at half maximum (FWHM) of 41 nm. Consequently, organic light emitting diodes (OLEDs) employing this emitter achieved a maximum external quantum efficiency (EQE_max) value of 27.7%, with minimal efficiency roll-off. Even at a practical luminance of 1000 cd∙m⁻², the device maintains a high EQE value of 24.6%.
- multi-resonance,
- narrowband emission,
- B−N covalent bond,
- organic light emitting diodes

Supplementary materials to this article can be found online at https://doi.org/10.1088/1674-4926/24040008.

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References

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Peripheral carbazole units-decorated MR emitter containing B−N covalent bond for highly efficient green OLEDs with low roll-off

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