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Article

New Polycyclic Red Luminescent Compounds Based on Carbonyl/Nitrogen Skeleton for Efficient Narrow-Spectrum OLEDs

by
Zhiwei Wu
1,
Peng Zou
1,
Ziwei Chen
1,
Ben Zhong Tang
2 and
Zujin Zhao
1,*
1
State Key Laboratory of Luminescent Materials and Devices, Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, South China University of Technology, Guangzhou 510640, China
2
Guangdong Basic Research Center of Excellence for Aggregate Science, School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen 518172, China
*
Author to whom correspondence should be addressed.
Materials 2025, 18(17), 4000; https://doi.org/10.3390/ma18174000
Submission received: 12 July 2025 / Revised: 15 August 2025 / Accepted: 20 August 2025 / Published: 26 August 2025
(This article belongs to the Special Issue Enhancement Strategies for High External Quantum Efficiency of Organic Light Emitting Diodes (OLEDs) and the Analyses)
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Abstract

Advances in OLED display technology have increased the demand for high-performance luminescent materials, yet efficient red emitters with narrow emission spectra remain rare. Here, two new polycyclic compounds (O-QA and S-QA) are designed by incorporating oxygen/sulfur into a carbonyl/nitrogen skeleton. Photophysical and theoretical studies reveal their hybridized local and charge-transfer state characteristics. In toluene, O-QA and S-QA show photoluminescence peaks at 586/579 nm with narrow emission spectra, while doped films exhibit strong red emissions peaking at 598/600 nm with high PL quantum yields of 67%/60%. The OLEDs using these emitters achieve red electroluminescence (EL) peaks at 598/602 nm, and attain maximum external quantum efficiencies of 7.36%/14.54%. This work may provide guidance for the development of narrow-spectrum red emitters based on carbonyl/nitrogen frameworks.

1. Introduction

Organic light-emitting diodes (OLEDs) have demonstrated remarkable progress in recent years, emerging as a highly promising technology for next-generation display and lighting [1,2]. The development of efficient and high color purity organic light-emitting materials is essential for the preparation of OLEDs for wide color gamut high-definition displays [3,4]. According to quantum spin statistics, the combination of holes and electrons in OLEDs normally forms 25% of the singlet excitons and 75% of the triplet excitons [5]. For most fluorescent materials, only singlet excitons can be harvested, which leads to low efficiencies of the devices. In recent years, researchers have devoted great efforts to enhance triplet exciton utilization of purely organic materials, and a variety of purely organic luminescent materials capable of utilizing triplet excitons via different photophysical mechanisms, including triplet–triplet annihilation (TTA) [6], hybridized local and charge-transfer (HLCT) [7,8], thermally activated delayed fluorescence (TADF) [9,10,11,12,13], room-temperature phosphorescence [14], and radical-based doublet emission [15,16]. The HLCT emitters represent an advanced class of organic luminescent materials that combine the advantages of locally excited (LE) and charge-transfer (CT) states. In this situation, the higher triplet state (T2 or Tn) can be transformed into the lowest singlet state (S1) by a high-lying reverse intersystem crossover (hRISC), which effectively improves the exciton collection capacity.
The full width at half maximum (FWHM) of the emission spectrum is one of the important influencing factors in OLED materials. A large full width at half maximum of the emission spectrum of luminescent compound may limit their use in high-definition displays, while narrow-spectrum luminescent materials are favored for achieving high color purity. In 2016, Hatakeyama et al. reported intriguing polycyclic aromatic materials embedded with boron atom and nitrogen atom [17], which have gained widespread attention owing to their unique multiple resonance (MR) property capable of realizing extremely narrow FWHM and excellent optoelectronic performance at the same time [18]. However, the syntheses of MR materials based on boron/nitrogen skeleton are quite complicated with low yields, which are not favorable for mass preparation. Recently, carbonyl/nitrogen skeletons are emerging as another option for developing narrow-spectrum materials [19,20]. Due to the short-range charge-transfer feature, the emissions of most carbonyl/nitrogen-based MR materials are currently located in the blue-green region, while those with emissions in the red region are relatively few [21,22].
In this work, we design and synthesize two new polycyclic luminescent compounds (O-QA and S-QA) based on carbonyl/nitrogen skeleton [23,24,25], which are induced to red-shifted emissions by increasing intramolecular charge-transfer effect by means of embedding S or O atoms (Figure 1). They have high molecular rigidity, which is conducive to achieving narrow emission spectra. O-QA and S-QA show strong photoluminescence (PL) emissions with peaks at 586 and 579 nm and narrow FWHMs of 48 and 64 nm in toluene solutions, respectively, and provide efficient red EL emissions in doped OLEDs with EL peaks at 598 and 602 nm, and good maximum external quantum efficiencies (EQEmaxs) of 7.36% and 14.54%, respectively.

2. Results and Discussion

2.1. Synthesis and Characterization

The target compounds (O-QA and S-QA) are synthesized by Ullmann coupling, hydrolysis, and Friedel–Crafts acylation reactions, and the synthetic routes are shown in Scheme 1. The structures of the intermediates and the final products are fully characterized by NMR (Figures S1–S6) and high-resolution mass spectrometry. The thermal properties of O-QA and S-QA are evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA shows that the decomposition temperature (Td, 5% initial weight loss) is 444 °C for both O-QA and S-QA (Figure S7a), implying the excellent thermal stability, which is beneficial for preparing vacuum-deposited OLED devices. The glass-transition temperatures are not found in DSC curves in the range of 100–300 °C (Figure S7b). Their electrochemical behaviors in dichloromethane are investigated by cyclic voltammetry (CV) (Figure S7c). O-QA and S-QA exhibit similar oxidation and reduction potentials, with highest occupied molecular orbital (HOMO) energy levels of −5.33 and −5.40 eV, respectively, and lowest unoccupied molecular orbital (LUMO) energy levels of −3.22 and −3.23 eV, respectively.

2.2. Theoretical Calculation

The geometrical and electronic structures of O-QA and S-QA are simulated by theoretical calculations (Figure 2a). From the optimized ground-state geometries, it is observed that both compounds exhibit distorted molecular configurations. S-QA has a larger dihedral angle of 53.3° between the central benzene ring (A ring) and the peripheral tilted benzene ring (B or B′ ring) relative to the dihedral angle of 40.3° for O-QA, probably due to the larger radius of S atom than O atom. In addition, the structural changes between ground (S0) and S1 states are further analyzed using root mean of squared displacement (RMSD). The results show that the conformational change of S-QA is greater than O-QA (Figure S8), and thus it is expected that the S-QA has broader emission spectrum than O-QA. Their HOMOs are delocalized throughout the entire molecular skeletons, whereas the LUMOs are mainly concentrated in the central parts, suggestive of the HLCT feature of both compounds.
For HLCT materials, their LE components provide high radiative transition rates and the CT components not only regulate the emission wavelengths but also open up hRISC processes, thus realizing full utilization of the triplet excitons [26,27]. The energy levels and electron-hole distributions of the excited states are calculated as well. As shown in Figure 2b, it is found that the lowest excited singlet (S1), lowest excited triplet (T1) and second triplet excited (T2) states have a mixture feature of LE and CT components, further confirming the presence of HLCT characteristics [28]. The natural transition orbit (NTO) calculation reveals that the HONTOs in S1, T1, and T2 states all have HLCT characteristics (Figure S9). The energy splitting (ΔEST) values between the S1 and T1 states are calculated as 0.59 and 0.52 eV for O-QA and S-QA, respectively. Such large ΔEST values indicate that it is difficult for them to have TADF properties. The energy gaps between T1 and T2 states of O-QA and S-QA are 0.68 and 0.60 eV, respectively, and such large energy difference is unfavorable for internal conversion from T2 to T1 states. Meanwhile, the energy level of T2 state lies close to that of S1 state, indicating hRISC from T2 to S1 states may occur, which is beneficial for the utilization of triplet excitons [29,30,31].

2.3. Photophysical Properties

The photophysical properties of both compounds in solution and doped film states are studied. The UV-vis absorption spectra of both compounds in toluene solutions have strong absorption bands below 400 nm from π-π* transitions (Figure 3a). The absorption maxima of O-QA and S-QA are located at 550 and 524 nm (Table 1), respectively, which are associated with CT states. O-QA and S-QA in toluene solutions show orange-red PL emissions with peaks at 586 and 579 nm, respectively. O-QA has a narrower FWHM of 48 nm than S-QA (64 nm) because of the more planar and rigid structure of O-QA [32]. On the other hand, the solvatochromic effects of O-QA and S-QA are studied in organic solvents with different polarity. As shown in Figure S10, the PL peaks of O-QA and S-QA are red-shifted along with the increase of solvent polarity, and the HLCT characteristics of O-QA and S-QA are confirmed by a two-section linear relationship between Stokes shift (va − vf) and solvent orientational polarizability f (ε, n), as fitted by the Lippert–Mataga model [33,34] (Figure 3b, Figure S10 and Tables S1 and S2). Meanwhile, both compounds exhibit single-exponential PL decay in toluene solutions (Figure S11), which is in good agreement with the HLCT feature. The absolute PL quantum yields (ΦPLs) of O-QA and S-QA in toluene solutions are 55% and 49%, respectively.
The doped films of O-QA and S-QA in the host of 9-(3-(9H-carbazol-9-yl)phenyl)-9H-3,9′-bicarbazole (mCPBC) (doping concentrations are 1 wt% for O-QA and 5 wt% for S-QA) show PL peaks at 598 and 600 nm, and FWHMs of 55 and 79 nm, respectively (Figure 3c). There are slight redshifts and broadening in PL spectra compared to those in toluene solutions, due to intermolecular interactions in the aggregated state. Their transient PL decay spectra in doped films show single-exponential decay with fitted lifetimes of 18.6 and 11.1 ns for O-QA and S-QA, respectively (Figure 3d), and no delay component are observed. Based on the fluorescence and phosphorescence spectra of the doped film at 77 K (Figure S12), the ΔEST values of O-QA and S-QA are estimated to be 0.29 and 0.26 eV, respectively. The large ΔEST values indicate that the TADF phenomenon could be difficult to occur. The ΦPLs of O-QA and S-QA in doped films are 67% and 60% respectively, and the radiative transition rates (kr) are 3.60 × 107 and 5.41 × 107 s−1, respectively.

2.4. Electroluminescence Behaviors

Considering the favorable photophysical properties and good thermal stability of these two compounds, their EL behaviors are further evaluated by fabricating doped devices with the structures of ITO/HATCN (5 nm)/TAPC (50 nm)/TCTA (5 nm)/mCP (5 nm)/EML (20 nm)/TmPyPB (70 nm)/LiF (1 nm)/Al. The doped films of these compounds with the doping concentrations of 1, 3, 5, and 10 wt% in mCPBC host function as emitting layers (EMLs), 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HATCN) and lithium fluoride (LiF) serve as hole-injection layers and electron-injection layers, respectively, 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) and tris(4-carbazoyl-9-ylphenyl)amine (TCTA) function as hole-transporting layers, 1,3-bis(carbazol-9-yl)benzene (mCP) works as exciton-blocking layer and electron-blocking layer, and 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene (TmPyPB) performs as electron-transporting layer. The EL performances of all the devices are summarized in Figure 4, Figure S13, and Table 2. O-QA and S-QA show the best EL results at 1 wt% and 5 wt% doping concentrations, respectively, which display narrow-spectrum red emissions with EL peaks at 598 and 602 nm, FWHMs of 56 and 76 nm, and CIE coordinates of (0.612, 0.384) and (0.601, 0.397), respectively. Their EL spectra are consistent with the PL spectra of the doped films, indicating that the emission originates from the radiative decay of the singlet excitons of O-QA and S-QA. Owing to the HLCT characteristics, O-QA and S-QA have good EL efficiencies with EQEmax of 7.36% and 14.54%, respectively, indicative of their potential applications in OLEDs.

3. Conclusions

In summary, two new luminescent compounds O-QA and S-QA are developed by adding oxygen or sulfur atoms to the polycyclic carbonyl/nitrogen skeleton. They are thermally stable, and show PL peaks at 586 and 579 nm with narrow FWHMs of 48 and 64 nm in toluene solutions, and slightly red-shifted PL peaks at 598 and 600 nm with FWHMs of 55 and 79 nm in doped films. Theoretical calculations and experimental measurements reveal that both compounds have HLCT characteristics and the hRISC process may occur in both compounds, which facilitates the utilization of triplet excitons and thus is conducive to improving EL performance. At a doping concentration of 1 wt%, the device of O-QA attains the best EL performance, with an EQEmax of 7.36%, an EL peak at 598 nm, a FWHM of 56 nm and CIE coordinate of (0.612, 0.384). For S-QA, at a doping concentration of 5 wt%, a better EQEmax of 14.54% is obtained, with an EL peak at 602 nm, a FWHM of 76 nm and CIE coordinates of (0.601, 0.397). These results indicate that both new polycyclic luminescent compounds have good potential in OLEDs. Meanwhile, the comparison of EQEmax suggests that S-QA has better EL performance than O-QA, and the introduction of sulfur-containing fragments has higher potential for further exploration of red luminescent materials for OLED. The structure relationship gained in this work could be helpful for further exploration of red luminescent materials with narrow emission spectra.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/ma18174000/s1, Figure S1: 1H NMR spectrum of compound 1 in DMSO-d6; Figure S2: 1H NMR spectrum of compound 3 in DMSO-d6; Figure S3: 1H NMR spectrum of compound O-QA in C2D2Cl4. Figure S4: 1H NMR spectrum of compound 2 in DMSO-d6. Figure S5: 1H NMR spectrum of compound 4 in DMSO-d6. Figure S6: 1H NMR spectrum of compound S-QA in C2D2Cl4. Figure S7: (a) TGA thermograms of O-QA and S-QA, recorded under nitrogen at a heating rate of 10 °C min−1, Td is decomposition temperature; (b) DSC thermograms of O-QA and S-QA, recorded under nitrogen at a heating rate of 10 °C min−1. (c) Cyclic voltammograms of O-QA and S-QA in dichloromethane. Figure S8: Comparison of optimized structures of O-QA and S-QA in S0 (pink) and S1 (blue) states. Figure S9: Natural transition orbital distributions of norm of highest occupied (HONTO) and lowest unoccupied natural transition orbital (LUNTO) of S1 state of O-QA and S-QA. Figure S10: (a) UV-vis absorption spectra and (b) PL spectra of O-QA, and (c) UV-vis absorption spectra and (d) PL spectra of S-QA in different solvents with varied polarity. Figure S11: Transient PL decay curves of O-QA and S-QA in toluene solutions. Figure S12: Fluorescence and phosphorescence spectra of O-QA (a) and S-QA (b) in doped films at 77 K. Figure S13: (a,b) EL spectra, (c,d) external quantum efficiency–luminance and (e,f) plots of luminance–voltage–current density of the OLEDs based on O-QA and S-QA doped in mCPBC host with different doping concentrations. Table S1: Absorption and emission peak positions of O-QA in different solvents. Table S2: Absorption and emission peak positions of S-QA in different solvents.

Author Contributions

Conceptualization, Z.Z.; methodology, Z.W., P.Z. and Z.Z.; validation, Z.W. and Z.Z.; formal analysis, Z.W.; investigation, Z.W. and Z.C.; data curation, Z.W. and Z.Z.; writing—original draft preparation, Z.W. and Z.Z.; writing—review and editing, Z.W., Z.C. and Z.Z.; visualization, Z.W. and Z.Z.; supervision, Z.Z. and B.Z.T.; project administration, Z.Z.; funding acquisition, Z.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This work was financially supported by the National Natural Science Foundation of China (U23A20594 and 22375066) and the GuangDong Basic and Applied Basic Research Foundation (2023B1515040003).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Wu, S.; Hu, Y.-N.; Sun, D.; Wang, K.; Zhang, X.-H.; Zysman-Colman, E. A Fluorene-Bridged Double Carbonyl/Amine Multiresonant Thermally Activated Delayed Fluorescence Emitter for Efficient Green OLEDs. Chem. Commun. 2024, 60, 2489–2492. [Google Scholar] [CrossRef]
  2. Li, S.; Li, M.; Li, Y.; Chu, S.; Gao, Y.; Yao, X.; Ji, W.; Li, G.; Ren, Z.; Fei, Z. High-Efficiency Solution-Processed Organic Light-Emitting Diodes Utilizing Multiple-Resonance Emitters Incorporating Thiocarbazole Unit. Adv. Opt. Mater. 2025, 13, 2403566. [Google Scholar] [CrossRef]
  3. Zou, Y.; Hu, J.; Yu, M.; Miao, J.; Xie, Z.; Qiu, Y.; Cao, X.; Yang, C. High-Performance Narrowband Pure-Red OLEDs with External Quantum Efficiencies up to 36.1% and Ultralow Efficiency Roll-Off. Adv. Mater. 2022, 34, 2201442. [Google Scholar] [CrossRef]
  4. Yu, Y.; Feng, Z.; Meng, X.; Chen, L.; Liu, F.; Yang, S.; Zhou, D.; Liao, L.; Jiang, Z. Introducing Spiro-locks into the Nitrogen/Carbonyl System towards Efficient Narrowband Deep-Blue Multi-Resonance TADF Emitters. Angew. Chem. Int. Ed. 2023, 62, e202310047. [Google Scholar] [CrossRef]
  5. Baldo, M.A.; O’Brien, D.F.; Thompson, M.E.; Forrest, S.R. Excitonic Singlet-Triplet Ratio in a Semiconducting Organic Thin Film. Phys. Rev. B 1999, 60, 14422–14428. [Google Scholar] [CrossRef]
  6. Chiang, C.; Kimyonok, A.; Etherington, M.K.; Griffiths, G.C.; Jankus, V.; Turksoy, F.; Monkman, A.P. Ultrahigh Efficiency Fluorescent Single and Bi-Layer Organic Light Emitting Diodes: The Key Role of Triplet Fusion. Adv. Funct. Mater. 2013, 23, 739–746. [Google Scholar] [CrossRef]
  7. Xu, Y.; Liang, X.; Zhou, X.; Yuan, P.; Zhou, J.; Wang, C.; Li, B.; Hu, D.; Qiao, X.; Jiang, X.; et al. Highly Efficient Blue Fluorescent OLEDs Based on Upper Level Triplet–Singlet Intersystem Crossing. Adv. Mater. 2019, 31, 1807388. [Google Scholar] [CrossRef]
  8. Feng, T.; Zhang, J.; Liu, D.; Li, W.; Wu, Y.; Fang, K.; Mu, X.; Liu, C.; Su, S.-J.; Ge, Z. Decoding the Impact of Molecular Configuration on High-Efficiency Blue Hot Exciton Emitters. Adv. Opt. Mater. 2024, 12, 2400652. [Google Scholar] [CrossRef]
  9. Uoyama, H.; Goushi, K.; Shizu, K.; Nomura, H.; Adachi, C. Highly Efficient Organic Light-Emitting Diodes from Delayed Fluorescence. Nature 2012, 492, 234–238. [Google Scholar] [CrossRef]
  10. Nathiya, S.; Panneerselvam, M.; Costa, L.T. A theoretical investigation of heavy atom and oxidation effects in MR-TADF emitters for OLEDs: A combined DFT, double hybrid DFT, CCSD, and QM/MM approaches. Chem. Chem. Phys. 2025, 27, 7265–7278. [Google Scholar] [CrossRef]
  11. Panneerselvam, M.; Kathiravan, A.; Solomon, R.V.; Jaccob, M. The role of π-linkers in tuning the optoelectronic properties of triphenylamine derivatives for solar cell applications–A DFT/TDDFT study. Phys. Chem. Chem. Phys. 2017, 19, 6153–6163. [Google Scholar] [CrossRef]
  12. Yang, T.; Liang, J.; Cui, Y.; Li, Z.; Peng, X.; Su, S.-J.; Wang, Y.; Li, C. Achieving 34.3% External Quantum Efficiency for Red Thermally Activated Delayed Fluorescence Organic Light-Emitting Diode by Molecular Isomer Engineering. Adv. Opt. Mater. 2023, 11, 2201191. [Google Scholar] [CrossRef]
  13. Yin, C.; Zhang, D.; Zhang, Y.; Lu, Y.; Wang, R.; Li, G.; Duan, L. High-Efficiency Narrow-Band Electro-Fluorescent Devices with Thermally Activated Delayed Fluorescence Sensitizers Combined Through-Bond and Through-Space Charge Transfers. CCS Chem. 2020, 2, 1268–1277. [Google Scholar] [CrossRef]
  14. Wu, X.; Peng, X.; Chen, L.; Tang, B.Z.; Zhao, Z. Through-Space Conjugated Molecule with Dual Delayed Fluorescence and Room-Temperature Phosphorescence for High-Performance OLEDs. ACS Mater. Lett. 2023, 5, 664–672. [Google Scholar] [CrossRef]
  15. Ai, X.; Evans, E.W.; Dong, S.; Gillett, A.J.; Guo, H.; Chen, Y.; Hele, T.J.H.; Friend, R.H.; Li, F. Efficient Radical-Based Light-Emitting Diodes with Doublet Emission. Nature 2018, 563, 536–540. [Google Scholar] [CrossRef]
  16. Yang, K.; Li, Z.; Huang, Y.; Zeng, Z. Bay/Ortho-Octa-Substituted Perylene: A Versatile Building Block toward Novel Polycyclic (Hetero)Aromatic Hydrocarbons. Acc. Chem. Res. 2024, 57, 763–775. [Google Scholar] [CrossRef]
  17. Hatakeyama, T.; Shiren, K.; Nakajima, K.; Nomura, S.; Nakatsuka, S.; Kinoshita, K.; Ni, J.; Ono, Y.; Ikuta, T. Ultrapure Blue Thermally Activated Delayed Fluorescence Molecules: Efficient HOMO-LUMO Separation by the Multiple Resonance Effect. Adv. Mater. 2016, 28, 2777–2781. [Google Scholar] [CrossRef]
  18. Kondo, Y.; Yoshiura, K.; Kitera, S.; Nishi, H.; Oda, S.; Gotoh, H.; Sasada, Y.; Yanai, M.; Hatakeyama, T. Narrowband Deep-Blue Organic Light-Emitting Diode Featuring an Organoboron-Based Emitter. Nat. Photon. 2019, 13, 678–682. [Google Scholar] [CrossRef]
  19. Yuan, Y.; Tang, X.; Du, X.-Y.; Hu, Y.; Yu, Y.-J.; Jiang, Z.-Q.; Liao, L.-S.; Lee, S.-T. The Design of Fused Amine/Carbonyl System for Efficient Thermally Activated Delayed Fluorescence: Novel Multiple Resonance Core and Electron Acceptor. Adv. Opt. Mater. 2019, 7, 1801536. [Google Scholar] [CrossRef]
  20. Fu, Y.; Zhuang, N.; Liu, H.; Wu, X.; Wu, Z.; Tang, B.Z.; Zhao, Z. Deciphering Intermediate Excited States in Spin-Flip Transition in Carbonyl-Nitrogen Multi-Resonance Molecule. Innov. Mater. 2025, 3, 100126. [Google Scholar] [CrossRef]
  21. Kim, H.J.; Yasuda, T. Narrowband Emissive Thermally Activated Delayed Fluorescence Materials. Adv. Opt. Mater. 2022, 10, 2201714. [Google Scholar] [CrossRef]
  22. Li, H.Z.; Xie, F.M.; Li, Y.Q.; Tang, J.X. Recent Progress and Prospects of Fluorescent Materials Based on Narrow Emission. J. Mater. Chem. C 2023, 11, 6471–6511. [Google Scholar] [CrossRef]
  23. Fan, X.C.; Wang, K.; Shi, Y.Z.; Chen, J.X.; Huang, F.; Wang, H.; Hu, Y.N.; Tsuchiya, Y.; Ou, X.M.; Yu, J.; et al. Managing Intersegmental Charge-Transfer and Multiple Resonance Alignments of D3-A Typed TADF Emitters for Red OLEDs with Improved Efficiency and Color Purity. Adv. Opt. Mater. 2022, 10, 2101789. [Google Scholar] [CrossRef]
  24. Wu, S.; Kumar Gupta, A.; Yoshida, K.; Gong, J.; Hall, D.; Cordes, D.B.; Slawin, A.M.Z.; Samuel, I.D.W.; Zysman-Colman, E. Highly Efficient Green and Red Narrowband Emissive Organic Light-Emitting Diodes Employing Multi-Resonant Thermally Activated Delayed Fluorescence Emitters. Angew. Chem. Int. Ed. 2022, 134, e202213697. [Google Scholar] [CrossRef]
  25. Wu, Z.; Zou, P.; Xu, J.; Dong, X.; Tang, B.Z.; Zhao, Z. Carbonyl-Nitrogen Multi-Resonance Emitters for Efficient OLEDs with High Color Purity. Commun. Chem. 2025, 8, 33. [Google Scholar] [CrossRef]
  26. Wang, Y.; Ma, Z.; Pu, J.; Guo, D.; Li, G.; Chen, Z.; Su, S.J.; Deng, H.; Zhao, J.; Chi, Z. Multiple-Resonance Thermally Activated Delayed Emitters through Multiple Peripheral Modulation to Enable Efficient Blue OLEDs at High Doping Levels. Aggregate 2024, 5, e585. [Google Scholar] [CrossRef]
  27. Wang, J.; Hafeez, H.; Tang, S.; Matulaitis, T.; Edman, L.; Samuel, I.D.W.; Zysman-Colm, E. Highly Efficient Organic Light-Emitting Diodes and Light-Emitting Electrochemical Cells Employing Multiresonant Thermally Activated Delayed Fuorescent Emitters with Bulky Donor or Acceptor Peripheral Groups. Aggregate 2024, 5, e571. [Google Scholar] [CrossRef]
  28. Zhong, Z.; Zhu, X.; Wang, X.; Zheng, Y.; Geng, S.; Zhou, Z.; Feng, X.J.; Zhao, Z.; Lu, H. High Steric-Hindrance Windmill-Type Molecules for Efficient Ultraviolet to Pure-Blue Organic Light-Emitting Diodes via Hybridized Local and Charge-Transfer Excited-State. Adv. Funct. Mater. 2022, 32, 2112969. [Google Scholar] [CrossRef]
  29. Jiang, R.; Liu, Z.; Han, Y.; Long, J.; Guo, T.; Lan, X.; Yu, M.; Fan, T.; Ma, H.; Wei, Y.; et al. Introducing Electron-Rich Thiophene Bridges in Hot Exciton Emitter for Efficient Non-Doped Near-Infrared OLEDs with Low Turn-on Voltages. Chem. Eng. J. 2024, 500, 157575. [Google Scholar] [CrossRef]
  30. Gan, X.; Ding, Z.; Liu, D.; Zheng, W.; Ma, B.; Zhang, H.; Chang, X.; Wang, L.; Liu, Y.; Wu, X.; et al. High-Efficiency and Narrow-Band Near-Ultraviolet Emitters with Low CIEy of 0.03 by Incorporating Extra Weak Charge Transfer Channel into Multi-Resonance Skeleton. Adv. Opt. Mater. 2023, 11, 2300195. [Google Scholar] [CrossRef]
  31. Wang, R.; Zhu, Y.; Hu, D.; Hu, J.; Chen, S.; Lin, J.; Xing, L.; Huo, Y.; Ji, S. Phosphorus-Oxygen Modified Anthracene-Based Emitters for High-Efficiency Deep-Blue OLEDs Approaching the BT.2020 Blue Standard. Chem. Eng. J. 2025, 506, 160269. [Google Scholar] [CrossRef]
  32. Jin, Z.; Wu, C.; Tong, K.N.; Shi, K.; Jung, S.; Li, S.; Wang, X.; Li, Z.; He, W.; Ye, M.; et al. Boosting Electroluminescence Efficiency Based on TADF Emitters Featuring Multiple Resonance Segment Integrated with a Co-Host Exciplex. Mater. Today Energy 2025, 49, 101833. [Google Scholar] [CrossRef]
  33. Wang, X.; Liu, Z.; Geng, S.; Zhong, Z.; Li, H.; Feng, X.J.; Zhao, Z.; Lu, H. Donor–Acceptor–Donor Molecules for High Performance Near Ultraviolet Organic Light-Emitting Diodes via Hybridized Local and Charge-Transfer Processes. J. Mater. Chem. C 2023, 11, 5316–5323. [Google Scholar] [CrossRef]
  34. Zheng, Y.; Zhu, X.; Wang, X.; Zhong, Z.; Feng, X.J.; Zhao, Z.; Lu, H. Bipolar Molecules with Hybridized Local and Charge-Transfer State for Highly Efficient Deep-Blue Organic Light-Emitting Diodes with EQE of 7.4% and CIEy ~0.05. Adv. Opt. Mater. 2021, 9, 2100965. [Google Scholar] [CrossRef]
Materials 18 04000 g001
Figure 1. Molecular structures for O-QA and S-QA.
Figure 1. Molecular structures for O-QA and S-QA.
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Scheme 1. Synthetic routes of O-QA and S-QA.
Scheme 1. Synthetic routes of O-QA and S-QA.
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Figure 2. (a) Optimized geometries and frontier orbital distribution of S0 state. (b) Calculated energy levels of singlet and triplet states and analysis of hole (blue) and electron (green) distributions.
Figure 2. (a) Optimized geometries and frontier orbital distribution of S0 state. (b) Calculated energy levels of singlet and triplet states and analysis of hole (blue) and electron (green) distributions.
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Materials 18 04000 g003
Figure 3. (a) Absorption and PL spectra in dilute toluene solutions (10−5 M) and (b) solvatochromic Lippert–Mataga plots of O-QA and S-QA. (c) PL spectra and (d) transient PL decay curves of O-QA and S-QA in doped films.
Figure 3. (a) Absorption and PL spectra in dilute toluene solutions (10−5 M) and (b) solvatochromic Lippert–Mataga plots of O-QA and S-QA. (c) PL spectra and (d) transient PL decay curves of O-QA and S-QA in doped films.
Materials 18 04000 g003
Materials 18 04000 g004
Figure 4. (a) Device configurations, (b) structures of functional layers, (c) external quantum efficiency–luminance plots (inset: EL spectra), (d) luminance–voltage–current density plots, and (e) CIE coordinates of doped devices of O-QA and S-QA.
Figure 4. (a) Device configurations, (b) structures of functional layers, (c) external quantum efficiency–luminance plots (inset: EL spectra), (d) luminance–voltage–current density plots, and (e) CIE coordinates of doped devices of O-QA and S-QA.
Materials 18 04000 g004
Table 1. Photophysical properties of O-QA and S-QA.
Table 1. Photophysical properties of O-QA and S-QA.
Compoundλabs (a)
[nm]		εmax (b)
[104]		λem (c)
[nm]		FWHM (d)
[nm]		ΔEST (e)
[eV]		ΦPL (f)
[%]		τ (g)
[ns]		kr (h)
[107 s−1]
O-QA5503.15586/59848/550.2955/6718.63.60
S-QA5242.28579/60064/790.2649/6011.15.41
(a) Absorption maximum (10−5 M); (b) Molar absorption coefficient corresponding to absorption maximum; (c) Emission peaks in toluene/doped film; (d) Full width at half maximum in toluene/doped film; (e) Singlet-triplet energy splitting in doped film; (f) Photoluminescence quantum yield in toluene/doped film; (g) Mean PL lifetime in doped films; (h) Radiative decay rate.
Table 2. EL performances of doped OLEDs based on O-QA and S-QA (a).
Table 2. EL performances of doped OLEDs based on O-QA and S-QA (a).
EmitterλEL
[nm]		Von
[V]		Lmax
[cd m−2]		CEmax
[cd A−1]		PEmax
[lm W−1]		EQEmax
[%]		CIE
(x, y)		FWHM
[nm]
1 wt% O-QA5983.7543913.5811.537.36(0.612, 0.384)56
3 wt% O-QA6023.6460111.189.76.70(0.625, 0.373)59
5 wt% O-QA6043.640398.707.595.46(0.629, 0.369)63
10 wt% O-QA6063.534945.715.133.80(0.634, 0.364)68
1 wt% S-QA5943.5778418.9617.018.76(0.578, 0.417)72
3 wt% S-QA5983.5739226.2023.5213.27(0.591, 0.405)73
5 wt% S-QA6023.4648226.6224.6014.54(0.601, 0.397)76
10 wt% S-QA6023.4648313.8912.848.02(0.607, 0.391)77
(a) Abbreviations: λEL = EL peak; Von = turn-on voltage at 1 cd m−2; Lmax = maximum luminance; CEmax = maximum current efficiency; PEmax = maximum power efficiency; EQEmax = maximum external quantum efficiency; CIE = Commission Internationale de I’Eclairage coordinates; FWHM = full width at half maximum.
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Wu, Z.; Zou, P.; Chen, Z.; Tang, B.Z.; Zhao, Z. New Polycyclic Red Luminescent Compounds Based on Carbonyl/Nitrogen Skeleton for Efficient Narrow-Spectrum OLEDs. Materials 2025, 18, 4000. https://doi.org/10.3390/ma18174000

AMA Style

Wu Z, Zou P, Chen Z, Tang BZ, Zhao Z. New Polycyclic Red Luminescent Compounds Based on Carbonyl/Nitrogen Skeleton for Efficient Narrow-Spectrum OLEDs. Materials. 2025; 18(17):4000. https://doi.org/10.3390/ma18174000

Chicago/Turabian Style

Wu, Zhiwei, Peng Zou, Ziwei Chen, Ben Zhong Tang, and Zujin Zhao. 2025. "New Polycyclic Red Luminescent Compounds Based on Carbonyl/Nitrogen Skeleton for Efficient Narrow-Spectrum OLEDs" Materials 18, no. 17: 4000. https://doi.org/10.3390/ma18174000

APA Style

Wu, Z., Zou, P., Chen, Z., Tang, B. Z., & Zhao, Z. (2025). New Polycyclic Red Luminescent Compounds Based on Carbonyl/Nitrogen Skeleton for Efficient Narrow-Spectrum OLEDs. Materials, 18(17), 4000. https://doi.org/10.3390/ma18174000

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