Modular construction of medium-to-long wavelength multi-resonant fluorescent emitters

Abstract

Efficient multiple resonance (MR) materials play a crucial role in display applications due to their extremely narrow bandwidth emission and high photoluminescence efficiency (Φ_PL). However, achieving a wide range of color tuning without compromising color purity remains a persistent challenge for MR emitters. This study introduces naphthalene, pyrene, anthracene, and perylene units through a simple modular approach to extend π-conjugation and facilitate wavelength shifts. Four MR fluorescent BNBCZ, BPBCZ, BFBCZ, and BPLBCZ emitters exhibit tunable narrowband emission characteristics from green to red in toluene, with spectra maxima at 509, 532, 559, and 605 nm, with full-width at half maximum values of 26, 29, 32, and 31 nm, respectively. Furthermore, all materials show high Φ_PLs of up to 95%. Notably, with the assistance of a thermally activated delayed fluorescence molecule, the sensitized organic light-emitting diodes based on these materials demonstrate good performances, achieving maximum external quantum efficiencies of 19.5%, 21.4%, 21%, and 23%, respectively, with low efficiency roll-off. The corresponding CIE coordinates of (0.24, 0.68) and (0.65, 0.35) closely align with the International Telecommunication Union's requirements for green and red electroluminescence.

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Introduction

Over the past decades, the development of organic light-emitting diodes (OLEDs) has been a subject of extensive research, primarily for their application potential in full-color displays and solid-state lighting, due to their advantages like lightweight structure, high brightness, low power consumption, wide viewing angle and fast response time, flexibility, ease of chemical tunability of the emitting molecules, etc.^1–6 But for the traditionally used fluorescence, phosphorescence and donor–acceptor type thermally activated delayed fluorescence (TADF) emitters used in OLEDs, the emission spectra are broad, which results in reduced color purity.^7–12 Therefore, they can’t meet the requirements of ultra-high-definition (UHD) displays with wide color gamut. Furthermore, according to the International Telecommunication Union recommendation BT 2020 standard for UHD displays, the emitter is required to achieve an emission spectrum with a narrow full width at half maximum (FWHM).¹³ In OLEDs for practical application, achieving high color purity typically necessitates the use of optical color filters or micro-cavities, which unfortunately results in substantial efficiency losses. Consequently, the development of efficient organic optoelectronic materials with intrinsic narrowband emission has become essential.

In 2016, Hatakeyama et al. reported the boron/nitrogen (B/N) based multi-resonance TADF (MR-TADF) emitter, DABNA-1, endowing 1,4-B/N-doped polycyclic aromatic hydrocarbons with alternatively localized highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO).¹⁴ Frontier molecular orbital (FMO) distributions within a rigid molecular framework have the capability to minimize both vibronic coupling and vibrational relaxation in the excited state, which results in outstanding photophysical properties, including a small singlet (S₁)–triplet (T₁) energy gap (ΔE_ST), a rapid radiative decay rate (k_r), a high photoluminescence efficiency (Φ_PL), and a narrow FWHM, etc. Since then, numerous heteroaromatic hydrocarbons with MR properties have been reported, including MR-TADF and MR fluorescence (MR-F) materials.^15–24

Due to the efficient harvesting of both S₁ and T₁ energies with maximum internal quantum efficiency (IQE_max) of 100% in OLEDs theoretically, the development of MR-TADF materials has attracted most researchers’ attention.^15–20 However, there are only several MR-F examples that have been reported, including N/B–N and N/B–C types, which endow the 1,4-B/N-doped structure and B–N bond with amine or the B–C bond with an aromatic ring. Though the theoretical IQE_max of MR-F materials is only 25%, the device efficiencies can be improved greatly with the help of suitable sensitizers.

In 2013, X. Feng et al. reported the first example of OLEDs based on B–N heteroarenes.²¹ In 2018, T. Hatakeyama et al. synthesized a corannulene possessing two B–N units, and employed it as an emitter for OLEDs.²² However, those B–N-backbones displayed an absent MR effect and inferior device performances.^21–25 In 2022, L. Duan et al. demonstrated the first implementation of easy-to-access MR-TADF molecules with B–N bonds, and the corresponding OLEDs showed impressive EQEs of >33.0% with alleviated efficiency roll-off.²⁶ Later, they further reported several efficient MR-TADF materials containing a similar molecular structure.^27,28

Compared with the emitters based on the N/B–N core, those containing an N/B–C core are all MR-F materials. But to date, there are only several examples that have been reported. In 2022, J. H. Kwon et al. developed the first N/B–C core-based MR-F materials, and the designed emitters BP-2DPA and DBP-4DPA (Fig. 1) exhibited narrowband pure red emissions peaking at 599 and 605 nm with a FWHM of 34 nm and high Φ_PLs of up to 96.4%. The corresponding sensitized OLEDs possessed EQE_max values of 11.3% and 15.1%, respectively.²¹ In 2023, C. Yang et al. constructed two MR-F emitters, Na-sBN and Na-dBN, by fusing B/N-doped moieties to naphthalene, and the materials manifested green and red emissions peaking at 516 and 612 nm with a FWHM of 31 nm, and near-unity Φ_PLs. The sensitized OLEDs exhibited high EQE_maxs as 28.8% and 25.2% with low efficiency roll-off.¹⁶ In 2024, Z. Bin et al. showcased two narrowband MR-F emitters, BN-NAP and BN-ANAP, by fusing of the meta-positioned double boron framework with two naphthalene moieties, emitting green emissions peaking at 511 and 518 nm with FWHMs of 26 and 20 nm, respectively. The sensitized OLED achieved an EQE_max of 21.0% with small efficiency roll-off.¹⁹

Fig. 1 The molecular structures of MR-F emitters based on B/N–C cores together with key photophysical characteristics.

From the above results it can be found that although the MR-F materials based on N/B–C core show low IQEs, the sensitized OLEDs also can exhibit high EQEs. Notably, the efficiency roll-off ratios of the corresponding devices are relatively low, suggesting their good device stability. However, only a few references about N/B–C core-based MR-F materials have been reported with limited emission colors. Therefore, in this work, we report four MR-F emitters with simple synthetic steps and relatively low molecular weights, achieving modular redshift emissions through the integration of polycyclic aromatic hydrocarbon fragments that extend the π-conjugation in the MR units (Fig. 1). By incorporating naphthalene, pyrene, and anthracene structures, the emissions of the synthesized BNBCZ, BPBCZ, BFBCZ, and BPLBCZ are gradually tuned from green to red, with spectrum peaks at 509, 532, 559, and 605 nm, respectively, in toluene. Furthermore, these molecules exhibit sharp emissions with narrow FWHMs and high Φ_PLs exceeding 88%. To efficiently harvest triplet excitons, TADF material sensitized OLEDs based on these materials were fabricated, achieving EQE_maxs of 19.5%, 21.4%, 21%, and 23%, respectively, with mild efficiency roll-off.

Results and discussion

Synthesis and characterization

This study incorporated naphthalene, pyrene, anthracene, and perylene units into the system, producing polycyclic aromatic hydrocarbons with B/N and B–C hybridization with multi-resonance effects. This approach modulates the emission color of the emitters while maintaining their narrowband emission spectra with high Φ_PLs.

The target compounds were synthesized through a three-step process, as depicted in Fig. 2 and Schemes S1–S4 (SI), involving a standard nucleophilic aromatic substitution reaction with 3,6-di-tert-butylcarbazole, followed by a palladium-catalyzed Suzuki coupling reaction in the presence of aqueous K₂CO₃. The starting materials include 4,4,5,5-tetramethyl-2-(naphthalen-1-yl)-1,3,2-dioxaborolane, 4,4,5,5-tetramethyl-2-(pyren-1-yl)-1,3,2-dioxaborolane, 2-(fluoranthen-3-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane and 4,4,5,5-tetramethyl-2-(perylen-3-yl)-1,3,2-dioxaborolane, combined with 9-(3-bromo-2-chlorophenyl)-3,6-di-tert-butyl-9H-carbazole. The final compounds BNBCZ, BPBCZ, BFBCZ, and BPLBCZ were subsequently synthesized via a chloride-lithium exchange reaction followed by one-pot borylation. All products were characterized using ¹H and ¹³C NMR spectroscopy (Fig. S1–S8, SI), high performance liquid chromatography (HPLC, Fig. S9–S16, SI), and elemental analysis. Additionally, all compounds exhibit excellent thermal stabilities, with decomposition temperatures (T_d, 5% weight-loss) of 449 °C for BNBCZ, 312 °C for BPBCZ, 460 °C for BFBCZ and 478 °C for BPLBCZ (Fig. S17, SI), respectively, which are conducive to the operational stability of devices.

Fig. 2 Synthesis routes for BNBCZ, BPBCZ, BFBCZ, BPLBCZ and their precursors.

To more precisely determine the molecular structural characteristics and study the intermolecular interactions, BNBCZ single crystal, slowly grown through a volatile method using CHCl₃/methanol solution, was analyzed via X-ray diffraction. The single-crystal diagram is shown in Fig. 3(a) and Fig. S18, and the crystal data are listed in Table S1 (SI). From Fig. 3(a) it can be observed that the molecule adopts a planar conformation with non-planar edges. According to the molecular design, the relatively twisted structure formed by the naphthalene moiety and the central benzene ring connected via B/N together with the significant steric hindrance of tert-butylcarbazole not only expands the π-conjugation of the emitting core but also suppresses close intermolecular π–π stacking interactions to reduce possible exciton quenching. The dihedral angles are 6.7° for the A/B rings, 6.67° for the A/C rings, 7.42° for the A/D rings, and 3.52° for the A/E rings. In the packing diagram, two molecules form a dimer with an intramolecular distance of 3.75 Å. The long distance suggests weak intermolecular interactions, providing more effective steric hindrance to reduce intermolecular aggregation.

Fig. 3 (a) Single crystal of BNBCZ (CCDC: 2386708; for clarity, hydrogen atoms and solvents have been omitted), and (b) HOMO and LUMO distributions.

Theoretical calculation

To determine the electronic and physical properties of the designed materials, density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were employed for both ground and excited states. All calculations were performed based on the B3LYP/6-31G(d) method, and the calculation results were visualized with the Multiwfn_3.8 and VMD software.²⁹ The theoretical HOMO and LUMO distributions of BNBCZ, BPBCZ, BFBCZ and BPLBCZ are shown in Fig. 3(b), and the related data are listed in Table S3.

The electron density distributions of the LUMO are similar for all molecules, primarily located on the B atom while those of the HOMO are mainly located on the N atom and partially on the naphthalene, pyrene, anthracene, and perylene units, respectively.

Photophysical properties

To investigate the photophysical properties of the four materials, the ultraviolet-visible (UV-vis) absorption and PL spectra of BNBCZ, BPBCZ, BFBCZ and BPLBCZ were measured in toluene, as shown in Fig. 4, and the resulting data are collected in Table 1. The bands observed below 400 nm are attributed to the n–π* and π–π* transitions of the molecules. While the strong absorption maxima at 485, 488, 491 and 581 nm correspond to intramolecular charge-transfer (ICT) absorption transitions of BNBCZ, BPBCZ, BFBCZ and BPLBCZ, respectively. In toluene, BNBCZ exhibits green luminescence peaking at 509 nm with a FWHM of 26 nm, and CIE coordinates of (0.18, 0.69). For BPBCZ, BFBCZ and BPLBCZ, the increased conjugation degree of pyrene, anthracene, and perylene units reduces the E_g gaps, resulting in red-shifted emissions peaking at 532, 559 and 609 nm with CIE coordinates of (0.31, 0.66), (0.47, 0.53), and (0.65, 0.35), respectively (Fig. S19, SI). Furthermore, the emission characteristics of the four compounds were found to be negligibly solvent-dependent in various polar solvents (Fig. S20, SI), consistent with their ICT-based nature.

Fig. 4 UV/vis absorption and steady-state PL spectra of BNBCZ, BPBCZ, BFBCZ and BPLBCZ in CH₂Cl₂ solution (10⁻⁵ M) at room temperature.

Table 1 Photophysical data and kinetic parameters of BNBCZ, BPBCZ, BFBCZ and BPLBCZ

Emitter	λ abs (nm)	λ PL (nm)	FWHM^c (nm)	CIE^d (x, y)	τ p (ns)	Φ PL (%)	S1^g (eV)	k r (10^8 s^−1)	E HOMO (eV)	E LUMO (eV)	E g (eV)
a UV-Vis absorption peak. b Photoluminescence peak. c Full width at half-maximum. d CIE color coordinates measured in toluene. e Prompt lifetime. f Photoluminescence quantum yield. g Singlet state level calculated by the fluorescence spectrum at 77 K. h k r = ΦF/τF. i Determined from cyclic voltammetry. j Calculated from EHOMO + Eg, the Eg estimated from the onset of the absorption spectrum.
BNBCZ	485	509	26	(0.18, 0.69)	7.05	95	2.54	1.35	−5.27	−2.72	2.55
BPBCZ	489	532	29	(0.31, 0.66)	11.84	88	2.43	0.75	−5.26	−2.72	2.54
BFBCZ	491	559	32	(0.47, 0.53)	7.25	90	2.32	1.24	−5.35	−2.83	2.52
BPLBCZ	581	609	31	(0.65, 0.35)	7.57	90	2.13	1.21	−5.31	−3.18	2.13

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Furthermore, the phosphorescence spectra recorded at 77 K in frozen toluene exhibit peak wavelengths of 534, 559, 581 and 635 nm for BNBCZ, BPBCZ, BFBCZ and BPLBCZ (Fig. S21, SI), respectively, and these values allowed for the estimation of the T₁ energy levels as 2.32, 2.21, 2.13 and 1.95 eV, respectively. Combined with the fluorescence spectra at 77 K, the levels of S₁ were estimated to be 2.54, 2.43, 2.32 and 2.13 eV, and the ΔE_ST values were calculated to be 0.22, 0.22, 0.11 and 0.18 eV for BNBCZ, BPBCZ, BFBCZ and BPLBCZ, respectively.

The doped films in mCBP (3,3′-di(9H-carbazol-9-yl)-1,1′-biphenyl) with a 5 wt% doped concentration of BNBCZ and BFBCZ exhibit PL spectra peaking at 512 and 541 nm with FWHM values of 27 and 32 nm, respectively. Moreover, doped films in DIC-TRZ (11-(4,6-diphenyl-1,3,5-triazin-2-yl)-12-phenyl-11,12-dihydroindolo[2,3-a]carbazole) with 5 wt% of BFBCZ and BPLBCZ exhibit the PL spectra maxima at 565 and 612 nm with FWHMs of 32 and 31 nm, respectively (Fig. S22, SI). Compared with those in toluene, the emission peaks of all the doped films red-shift about 3–6 nm due to the aggregation of the emitters and host–guest interaction. Furthermore, all the doped films of BNBCZ, BPBCZ, BFBCZ and BPLBCZ have high Φ_PL values of 95%, 88%, 90% and 90% (Fig. S24–S27, SI), respectively. Furthermore, the transient PL curves of all emitters exhibit single exponential character, and no delayed components were observed. The BNBCZ, BPBCZ, BFBCZ and BPLBCZ doped films exhibit prompt decay lifetimes (τ_p) of 7.05, 11.84, 7.25 and 7.57 ns, respectively (Fig. S28, SI), which indicates that all materials are fluorescent materials. In addition, based on the prompt lifetimes and photoluminescence efficiencies, the rate constants for radiative (k_r) singlet excitons were calculated, which are 1.35 × 10⁸ s⁻¹ for BNBCZ, 0.75 × 10⁸ s⁻¹ for BPNCZ, 1.24 × 10⁸ s⁻¹ for BFBCZ and 1.21 × 10⁸ s⁻¹ for BPLBCZ, respectively. The high values suggest that these materials are potential emitters for OLED applications.

Cyclic voltammetry (CV) measurements were also performed on BNBCZ, BPBCZ, BFBCZ and BPLBCZ to estimate their HOMO and LUMO energy levels. As shown in Fig. S29 (SI), from the onsets of the oxidation peaks of the CV curves, their HOMO/LUMO energy levels were calculated as −5.27/2.72 eV for BNBCZ, −5.26/2.72 eV for BPBCZ, −5.35/2.83 for BFBCZ, and −5.31/3.18 eV for BPLBCZ, respectively (Table. S2, SI).

Electroluminescent property

To evaluate the electroluminescence (EL) behaviors of BNBCZ, BPBCZ, BFBCZ and BPLBCZ emitters and to demonstrate our design strategy, multilayer devices were fabricated with the configuration of ITO (indium-tin oxide)/HAT-CN (1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile, 10 nm)/TAPC (1,1-bis[4-[N,N-di(p-tolyl)amino]phenyl]cyclohexane, 40 nm)/mCBP (3,3-di(9H-carbazol-9-yl)biphenyl, 5 nm)/emissive layer (20 nm)/TmPyPB (1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene, 50 nm)/LiF (1 nm)/Al (120 nm), and the OLEDs employing BNBCZ, BPBCZ, BFBCZ and BPLBCZ as emitters are denoted as D-BNBCZ, D-BPBCZ, D-BFBCZ and D-BPLBCZ, respectively. Within the devices, HAT-CN and TAPC served as hole injection and transporting layers, respectively. mCBP acted as an exciton-blocking layer, and TmPyPB was employed as an electron transporting layer. LiF and Al were used as the electron injection layer and cathode, respectively. Initially, using BNBCZ as an example, a device was prepared with a mass fraction of 5 wt% into an mCBP matrix. Unfortunately, due to the inherently low IQEs of fluorescent molecules in OLEDs, the EQE_max value was below 5% (Fig. S30).

To enhance the device efficiency, devices were fabricated using a sensitization technique employing different TADF materials as sensitizers. Respectively, in the emission layers of the D-BNBCZ and D-BPBCZ devices, mCBP was used as the host, and 5tczBN (2,3,4,5,6-pentakis(3,6-di-tert-butyl-9H-carbazol-9-yl)benzonitrile) and DACT-II (9-[4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-N³,N³,N⁶,N⁶-tetraphenyl-9H-carbazole-3,6-diamine) were applied as the TADF sensitizers, respectively. But in the emission layers of the D-BFBCZ and D-BPLBCZ devices, a TADF material of DIC-TRZ was selected as the host, and DMAC-BP Bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]methanone was applied as the TADF assistant host in the emissive layer to transfer sufficient energy to fluorescent emitters. The chemical structures of the OLED materials and the energy level diagrams for each device are shown in Fig. S31 (SI), while the EL spectra and CIE photograph, current density – voltage – luminance (J–V–L) and EQE – luminance (EQE – L) characteristics are presented in Fig. 5, with the detailed device performance data provided in Table 2 and Table S5 (SI).

Fig. 5 (a) Normalized EL curves, (b) CIE(x, y) coordinates of the BNBCZ, BPBCZ, BFBCZ and BPLBCZ devices, (c) current density and luminance versus voltage curves, and (d) EQE versus luminance characteristics.

Table 2 Device performances of D-BNBCZ, D-BPBCZ, D-BFBCZ and D-BPLBCZ

Device	V on (V)	λ EL (nm)	FWHM^c (nm/eV)	CIE^d (x, y)	L max (cd m^−2)	CEmax^f (cd A^−1)	PEmax^g (lm W^−1)	EQEmax^h (%)
a Turn-on voltage at 1 cd m^−2. b Electroluminescence peak. c Full width at half maximum of electroluminescence spectrum. d CIE color coordinates measured at 5 V. e Maximum luminance. f Maximum current efficiency. g Maximum power efficiency. h Maximum external quantum efficiency.
D-BNBCZ	3.9	519	40/0.12	(0.24, 0.68)	195 852	76	62	19.5
D-BPBCZ	4.1	546	45/0.10	(0.43, 0.57)	185 733	82	79	23.5
D-BFBCZ	4.1	569	37/0.13	(0.52, 0.48)	154 295	64	62	21.4
D-BPLBCZ	3.7	610	31/0.15	(0.65, 0.35)	174 352	34	36	23.3

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As shown in Fig. 5(a), the OLEDs containing 5tczBN: BNBCZ, DACT-II: BFBCZ, DMAC-BP: BPBCZ, and DMAC-BP: BPLBCZ with a 5 wt% doped concentration exhibit narrowband EL spectra with peaks at 519, 546, 569, and 610 nm, and corresponding FWHM values of 40, 45, 37, and 31 nm, respectively. The EL spectra are consistent with the photoluminescence spectra of emitters in doped films with narrow FWHMs, suggesting the efficient and complete energy transfer from the TADF sensitizers to the emitters. Benefiting from the narrow emission bandwidths and precise wavelengths, the D-BNBCZ, D-BFBCZ, D-BPBCZ, and D-BPLBCZ devices show CIE coordinates of (0.24, 0.68), (0.43, 0.57), (0.52, 0.48), and (0.65, 0.35), respectively. The measured CIE coordinates of the D-BNBCZ and D-BPLBCZ devices exhibit close proximity to the International Telecommunication Union green (CIE: 0.21, 0.71) and red (CIE: 0.67, 0.33) standards, respectively.

All TADF sensitized OLEDs show good device performances, and the D-BPLBCZ-doped device achieves the lowest turn-on voltage of 3.7 V (V_on, at 1 cd m⁻²) due to the lowest LUMO energy level of the BPLBCZ (3.58 eV) among the four emitters, which favors the TmPyPB electron injection into the luminescent layer. The maximum luminance of the D-BNBCZ, D-BFBCZ, D-BPBCZ, and D-BPLBCZ devices reaches 195 852, 185 733, 154 295, and 174 352 cd m⁻², respectively. And the corresponding maximum current efficiencies (CE_max) and power efficiencies (PE_max) are 76, 82, 64, and 34 cd A⁻¹, and 62, 79, 62, and 36 lm W⁻¹, respectively. The results indicate that both electrogenerated S₁ and T₁ excitons were effectively harvested and utilized for EL. The EQE_max of the D-BNBCZ reaches 19.5%, retaining 15.8% and 13.1% at practical luminance levels of 100 and 1000 cd m⁻², respectively. The D-BPBCZ demonstrates a peak EQE_max of 23.5%, maintaining high EQE values of 20.4% and 17.7% at practical luminance levels of 100 and 1000 cd m⁻², respectively. Similarly, the BFBCZ device has an EQE_max of 21.4%, with EQEs of 17.8% and 16.8% at 100 and 1000 cd m⁻², respectively. The BPLBCZ device also shows good performance, with an EQE of 23.3%, sustaining 20.0% and 18.0% at 100 and 1000 cd m⁻². These results confirm that all four MR-F emitter-based OLEDs exhibit high efficiency with relatively low efficiency roll-off, highlighting their potential for practical applications in high-performance electroluminescent devices. Furthermore, as the driving voltage increased from 5 to 9 V, the EL spectra of the four types of OLEDs exhibit minimal change (Fig. S32, SI), indicating their good spectral stability.

Conclusions

In conclusion, four wide-gamut narrow-band fluorescence materials with significant multiple resonance effects were successfully synthesized. These emitters exhibit good photophysical properties, with emission peaks at 519, 546, 569, and 610 nm, and FWHM values of 40, 45, 37, and 31 nm, respectively, in thin films. All doped films of these emitters demonstrate Φ_PL values exceeding 88%. Notably, with the assistance of thermally activated delayed fluorescence molecules, the sensitized OLEDs based on these materials show good performances, achieving EQE_maxs of 19.5%, 21.4%, 21%, and 23%, respectively, with relative low efficiency roll-off ratios. This study presents a novel method for constructing color-tunable multiple resonance materials, opening new possibilities for various OLED display technology applications.

Author contributions

Wei and Liang contributed equally to this work. Yi Wei: conceptualization, data curation, formal analysis, investigation, methodology, visualization, writing – original draft. Jia-Qi Liang: data curation, investigation, validation. Li Yuan: project administration, validation. Jia-Jun Hu: project administration, software. Shuai Xing: project administration, validation. Zhong-Zhong Huo: project administration, validation. Wen-Wei Zhang: project administration, resources. Y-X Zheng: conceptualization, funding acquisition, project administration, resources, supervision, writing – review & editing.

Conflicts of interest

The authors declare no conflict of interest.

Data availability

The authors declare that the data supporting the findings of this study are available within the paper and its supplementary information files, including the synthesis and characterization (¹H and ¹³C NMR, HPLC spectra) details of precursors and products, thermal gravimetric analysis curves, crystal data, photophysical properties, cyclic voltammogram curves and theoretical calculations of four compounds, supplementary information of their corresponding OLEDs. Should any raw data files be needed in another format they are available from the corresponding author upon reasonable request.

Supplementary information is available. See DOI: https://doi.org/10.1039/d5tc02297e.

CCDC 2386708 contains the supplementary crystallographic data for this paper.³⁰

Acknowledgements

This work was supported by the Natural Science Foundation of Jiangsu Province (BK20242021).

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Footnote

† Yi Wei and Jia-Qi Liang contributed equally to this work.

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