Dibenzophenazine‐Based TADF Emitters as Dual Electrochromic and Electroluminescence Materials

Crocomo, Paola Zimmermann; Okazaki, Masaki; Hosono, Takumi; Minakata, Satoshi; Takeda, Yoshifumi; Data, Przemysław

doi:10.1002/chem.202200826

Cited by 6 publications

(5 citation statements)

References 34 publications

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“…29 While it might be assumed that a single D−A unit is sufficient to ). 30 The appropriate choice of a host matrix [4,4′,4′′-tris(N-3methylphenyl-N-phenyl-amino)-triphenylamine: m-MTDA-TA] for the fabrication of an OLED-enabled near-infrared emission (λ em 741 nm) from an exciplex between the emitter and the host material is noteworthy (Figure 3e). This represents one of the earliest examples of near-infrared TADF from a TADF exciplex.…”

Section: Enhancing Ct Character For Efficient Tadf Manifestationmentioning

confidence: 99%

“…The external quantum efficiency (EQE) of the device (DEV 3, Figure d) reached a very high value (16%) for orange TADF-OLED. Further optimization of device configurations by adding a hole injection layer (2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene: HAT-CN) and removing an extra electron-transporting layer (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline: BCP) achieved an EQE close to the theoretical maximum (20.5%) …”

Section: Introductionmentioning

confidence: 96%

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Modulating the Photophysical Properties of Twisted Donor–Acceptor–Donor π-Conjugated Molecules: Effect of Heteroatoms, Molecular Conformation, and Molecular Topology

Takeda

2024

Acc. Chem. Res.

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Metrics & MoreArticle Recommendations CONSPECTUS: Modulating the photophysical properties of organic emitters through molecular design is a fundamental endeavor in materials science. A critical aspect of this process is the control of the excited-state energy, which is essential for the development of triplet exciton-harvesting organic emitters, such as those with thermally activated delayed fluorescence and roomtemperature phosphorescence. These emitters are pivotal for developing highly efficient organic light-emitting diodes and bioimaging probes. A particularly promising class of these emitters consists of twisted donor− acceptor organic π-conjugated scaffolds. These structures facilitate a spatial separation of the frontier molecular orbitals, which is crucial for achieving a narrow singlet−triplet energy gap. This narrow gap is necessary to overcome the endothermic reverse intersystem crossing process, enhancing the efficiency of thermally activated delayed fluorescence. To precisely modulate the photophysical properties of these emitting materials, it is essential to understand the electronic structures of new donor−acceptor scaffolds, especially those influenced by heteroatoms, as well as their conformations and topologies. This understanding not only improves the efficiency of these emitters but also expands their potential applications in advance technologies.In 2014, the Takeda group made a significant breakthrough by discovering a novel method for synthesizing U-shaped diazaacenes (dibenzo[a,j]phenazine) through an oxidative skeletal rearrangement of 1,1′-binaphthalene-2,2′-diamines. This class of compounds is typically challenging to synthesize using conventional organic reactions. The resulting unique geometric and electronic structure of U-shaped diazaacenes opened new possibilities for photophysical applications. Leveraging the U-shaped structure, photoluminescent properties, and high electron affinity, we developed twisted donor−acceptor−donor compounds. These compounds exhibit efficient thermally activated delayed fluorescence, stimuli-responsive luminochromism, heavy atom-free room-temperature phosphorescence, and anion-responsive red shifts. These innovative emitters have demonstrated significant potential in various practical applications, including organic light-emitting diode devices and advanced sensing systems. In this Account, I summarize our achievements in modulating the photofunctions of dibenzo[a,j]phenazine-cored twisted donor− acceptor−donor compounds by controlling excited-state singlet−triplet energy gaps through conformational regulation. Our comprehensive studies revealed the significant impact of heteroatoms, molecular conformations, and topologies on the photophysics of these compounds. These findings highlight the importance of molecular engineering in tailoring the photophysical properties of organic donor−acceptor π-conjugated materials for specific applications. Our research has demonstrated that incorporating heteroatoms into the molecular framework effectively tunes the...

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Section: Enhancing Ct Character For Efficient Tadf Manifestationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Modulating the Photophysical Properties of Twisted Donor–Acceptor–Donor π-Conjugated Molecules: Effect of Heteroatoms, Molecular Conformation, and Molecular Topology

Takeda

2024

Acc. Chem. Res.

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“… [7] In a device an external quantum efficiency of up to 0.205 could be achieved, making POZ‐DBPHZ a promising orange TADF emitter. [10] It was shown that the torsion angle between D and A units is nearly 90°. [5] This causes the required separation of electron and hole densities and reduces

to 20 meV, highlighting the importance of three‐dimensional conformations.…”

Section: Introductionmentioning

confidence: 99%

“…One notable example is POZ‐DBPHZ, a D−A−D triad with two phenoxazine (POZ) moieties bridged by a central DBPHZ unit [7] . In a device an external quantum efficiency of up to 0.205 could be achieved, making POZ‐DBPHZ a promising orange TADF emitter [10] . It was shown that the torsion angle between D and A units is nearly 90° [5] .…”

Section: Introductionmentioning

confidence: 99%

Femtosecond Spectroscopy on a Dibenzophenazine‐Cored Macrocycle Exhibiting Thermally Activated Delayed Fluorescence

et al. 2023

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The photophysics of a thermally activated delayed fluorescence (TADF) emitting macrocycle consisting of two dibenzo[ a,j ]phenazine acceptor moieties bridged by two N,N,N’,N’ ‐tetraphenylene‐1,4‐diamine donor units was scrutinized in solution by steady‐state and time‐resolved spectroscopy. The fluorescence lifetime of the compound proved to be strongly solvent‐dependent. It ranges from 6.3 ns in cyclohexane to 34 ps in dimethyl sulfoxide. In polar solvents the fluorescence decay is predominantly due to internal conversion. In non‐polar ones radiative decay and intersystem crossing contribute. Contrary to the behaviour in polymer matrices (S. Izumi et al., J. Am. Chem. Soc . 2020 , 142 , 1482) the excited state decay is not predominantly due to prompt and delayed fluorescence. The solvent‐dependent behaviour is analyzed with the aid of quantum chemical computations.

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“…The most basic principle of electrochromic materials is their electron-transfer activity, in which molecules gain and lose electrons through REDOX reactions, presenting reversible color changes at different voltage values [ 14 , 15 , 16 , 17 ]. In the research, the process of natural selection is an inevitable process when developing materials; from the beginning stage of simple inorganic discoloration to the present organic oligomer’s structure, the field of electrochromic materials has experienced dramatic changes [ 18 , 19 , 20 ].…”

Section: Introductionmentioning

confidence: 99%

D–A Structural Oligomers Containing Benzothiadiazole or Benzophenone as Novel Multifunctional Materials for Electrochromic and Photodetector Devices

Mei

Chu

et al. 2023

Polymers

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In this study, six conjugated oligomers containing D–A structures were synthesized using the Stille coupling reaction and named PHZ1–PHZ6. All the oligomers utilized demonstrated excellent solubilities in common solvents and notable color variations in the domain of electrochromic characteristics. By designing and synthesizing two electron-donating groups modified with alkyl side chains and a common aromatic electron-donating group, as well as cross-binding them with two electron-withdrawing groups with lower molecular weights, the six oligomers presented good color-rendering efficiencies, among which PHZ4 presented the best color-rendering efficiency (283 cm2·C−1). The products also demonstrated excellent electrochemical switching-response times. PHZ5 presented the fastest coloring time (0.7 s), PHZ3 and PHZ6 presented the fastest bleaching times (2.1 s). Following 400 s of cycling activity, all the oligomers under study showed good working stabilities. Moreover, three kinds of photodetectors based on conducting oligomers were prepared, and the experimental results show that the three photodetectors have better specific detection performances and gains. These characteristics indicate that oligomers containing D–A structures are suitable for use as electrochromic and photodetector materials in the research.

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Dibenzophenazine‐Based TADF Emitters as Dual Electrochromic and Electroluminescence Materials

Cited by 6 publications

References 34 publications

Modulating the Photophysical Properties of Twisted Donor–Acceptor–Donor π-Conjugated Molecules: Effect of Heteroatoms, Molecular Conformation, and Molecular Topology

Modulating the Photophysical Properties of Twisted Donor–Acceptor–Donor π-Conjugated Molecules: Effect of Heteroatoms, Molecular Conformation, and Molecular Topology

Femtosecond Spectroscopy on a Dibenzophenazine‐Cored Macrocycle Exhibiting Thermally Activated Delayed Fluorescence

D–A Structural Oligomers Containing Benzothiadiazole or Benzophenone as Novel Multifunctional Materials for Electrochromic and Photodetector Devices

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