Near-ultraviolet emitters based on carbazole-imidazole for highly efficient solution-processed organic light-emitting diodes

Liu, Siyang; Li, Junzi; Yan, Hongxia; Ye, Fanghao; Niu, Fangfang; Zhang, Bin; Wang, Guoping; Li, Guijun; Zeng, Peng

doi:10.1016/j.cej.2022.138881

Cited by 11 publications

(2 citation statements)

References 42 publications

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“…Imidazole is a reactive aromatic ring, which can be easily functionalized with aryl and alkyl groups to tune the cation size, as well as overall thermal and photophysical properties. [43,44] Moreover, the luminescence of imidazolium-based manganese halides was reported before, [1] proving the feasibility of this synthetic approach. However, information on the photophysical properties of imidazolium-based manganese halides, especially their photoluminescence quantum yields, is still quite limited.…”

Section: Introductionmentioning

confidence: 64%

Photophysical Tuning of Imidazolium Tetrahalidomanganate(II) Complexes towards Highly Efficient Green Emitters with Near‐Unity Quantum Yield

Sääsk,

Chen,

Huang

et al. 2023

Eur J Inorg Chem

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Ten ionic manganese(II) complexes of [EMIm]2[MnX2Y2] (EMIm = 1‑ethyl‐3‐methylimidazolium ion; X, Y = Cl, Br or I) and [BnMIm]2[MnX2Y2] (BnMIm = 1‐benzyl‐3‐methylimidazolium ion; X, Y = Cl, Br or I) types were synthesized and studied in terms of their thermal and photophysical properties. Complexes with [BnMIm]+ cation were found to exhibit higher crystallinity, owing to the aromatic π‐stacking, and superior photoluminescent quantum yields, promoted by the increased Mn⋯Mn distance. For complexes with chlorine and bromine ligands efficient tunability of photophysical parameters was demonstrated. Out of all complexes, [BnMIm]2[MnBr4] was found to have the highest photoluminescence quantum yield at room temperature (Φ = 0.59). To highlight the importance of a large Mn⋯Mn distance for achieving high Φ values, a mixed‐anion analog of complex [BnMIm]2[MnBr4] was prepared, with the suggested formula of [BnMIm]4[MnBr4]Br2. The latter have shown a significant improvement in d–d absorption efficiency and a reduction in nonradiative deactivation, which led to an outstanding Φ value of 0.97. Finally, the optical band gap of [BnMIm]4[MnBr4]Br2 was estimated to describe its applicability as light‐emitting material.

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Section: Introductionmentioning

confidence: 64%

Photophysical Tuning of Imidazolium Tetrahalidomanganate(II) Complexes towards Highly Efficient Green Emitters with Near‐Unity Quantum Yield

Sääsk,

Chen,

Huang

et al. 2023

Eur J Inorg Chem

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“…The 5% weight loss is 413 ○ C (PIMP), 397 ○ C (PIPP), 370 ○ C (PIPM), and 356 ○ C (PIMM) due to the primary decomposition may be ascribed to the breaking of N1 subunits of the fluorophores. The final breakdown of the fluorophores occurs above 460 ○ C, which may be caused by the fragments of alkyl spacer, carbazole, and phenanthroimidazole (PI). , Additionally, by employing DSC measurement, the melting temperature ( T m ) was determined to be 154 ○ C (PIMP), 145 ○ C (PIPP), 136 ○ C (PIMM), and 128 ○ C (PIPM) (shown in Figure b). These results suggest that the synthesized fluorophores are well suited for OLED device.…”

Section: Resultsmentioning

confidence: 99%

Molecular Modulation by σ Conjugated Spacer Enables Efficient Ultraviolet/Deep-Blue Emissive Organic Light-Emitting Diodes

et al. 2023

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Phenanthroimidazole (PI) has great proficiency to design efficient near UV deep blue emitting materials due to its bipolarity behavior. The tuning of N1 and C1 centers of the PI further reveals the improvement of the optical and electronical properties. Thorough investigation is also executed to explore the influence of the alkyl chain on the optical and electroluminescence (EL) properties of these emissive materials. The incorporation of the alkyl chain in the materials can tune the optical properties, leading to better solid state emission and enhancement of the photoluminescence quantum yield (PLQY) of thin film (∼74%) as compared to solution (∼65%). The EL spectra were also exhibited between 395 and 420 nm (in the near-UV spectral region). Furthermore, for boosting of the device efficiency and color purity, the OLED device is fabricated by doping CBP as host matrix. Selectively, CBP is used as a host because of the similar energy level (HOMO and LUMO) of the synthesized emitters which assist efficient charge trapping. Predominantly, the emitters in OLED device blended with 0.5 wt % concentration achieved brilliant device efficiency and luminance properties. Among all the synthesized fluorophores, PIPP (0.5 wt %) doped OLED device showed 4.4% maximum external quantum efficiency (EQEmax), 1202 cd/m2 highest luminance, 2.2 lm/W power efficiency (PE), 2.7 cd/A current efficiency (CE) with Commission International de L’Eclairage (CIE) coordinates x = 0.17, y = 0.10 (nearer the NTSC standard value).

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Boosting External Quantum Efficiency to 12.0 % of an Ultraviolet OLED by Engineering the Horizontal Dipole Orientation of a Hot Exciton Emitter

Zhang,

Zhou,

Liu

et al. 2024

Angewandte Chemie

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Currently, much research effort has been devoted to improving the exciton utilization efficiency and narrowing the emission spectra of ultraviolet (UV) fluorophores for organic light‐emitting diode (OLED) applications, while almost no attention has been paid to optimizing their light out‐coupling efficiency. Here, we developed a linear donor‐acceptor‐donor (D‐A‐D) triad, namely CDFDB, which possesses high‐lying reverse intersystem crossing (hRISC) property. Thanks to its integrated narrowband UV photoluminescence (PL) (λPL: 397 nm; FWHM: 48 nm), moderate PL quantum yield (φPL: 72%, Tol), good triplet hot exciton (HE) conversion capability, and large horizontal dipole ratio (Θ//: 92%), the OLEDs based on CDFDB not only can emit UV electroluminescence with relatively good color purity (λEL: 398 nm; CIEx,y: 0.161, 0.040), but also show a record maximum external quantum efficiency (EQEmax) of 12.0%. This study highlights the important role of horizontal dipole orientation engineering in the molecular design of HE UV‐OLED fluorophores.

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Near-ultraviolet emitters based on carbazole-imidazole for highly efficient solution-processed organic light-emitting diodes

Cited by 11 publications

References 42 publications

Photophysical Tuning of Imidazolium Tetrahalidomanganate(II) Complexes towards Highly Efficient Green Emitters with Near‐Unity Quantum Yield

Photophysical Tuning of Imidazolium Tetrahalidomanganate(II) Complexes towards Highly Efficient Green Emitters with Near‐Unity Quantum Yield

Molecular Modulation by σ Conjugated Spacer Enables Efficient Ultraviolet/Deep-Blue Emissive Organic Light-Emitting Diodes

Boosting External Quantum Efficiency to 12.0 % of an Ultraviolet OLED by Engineering the Horizontal Dipole Orientation of a Hot Exciton Emitter

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