Electroluminescent room temperature columnar liquid crystals based on bay-annulated perylene tetraesters

Gupta, Ravindra; Das, Dipjyoti; Gupta, Monika; Pal, Santanu Kumar; Iyer, Parameswar Krishnan; Achalkumar, Ammathnadu S.

doi:10.1039/c6tc04166c

Cited by 47 publications

(50 citation statements)

References 48 publications

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“…This has led to transformed aromatic systems with fascinating properties. Incorporation of sulfur and selenium in organic semiconductors is widely explored due to the intermolecular S⋅⋅⋅S and Se⋅⋅⋅Se interactions, which also help to stabilize the molecular self‐assembly and hence improve 1D conductivity –. Motivated by our success in stabilizing luminescent Col self‐assembly in hetero atom bay‐annulated PTEs over a wide thermal range, we envisaged the synthesis of their bisimide counterparts.…”

Section: Introductionmentioning

confidence: 91%

Columnar Self‐Assembly of Electron‐Deficient Dendronized Bay‐Annulated Perylene Bisimides

Gupta

Rao

Prasad

et al. 2018

Chemistry A European J

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Three new heteroatom bay-annulated perylene bisimides (PBIs) have been synthesized by microwave-assisted synthesis in excellent yield. N-annulated and S-annulated perylene bisimides exhibited columnar hexagonal phase, whereas Se-annulated perylene bisimide exhibited low temperature columnar oblique phase in addition to the high temperature columnar hexagonal phase. The cup shaped bay-annulated PBIs pack into columns with enhanced intermolecular interactions. In comparison to PBI, these molecules exhibited lower melting and clearing temperature, with good solubility. A small red shift in the absorption was seen in the case of N-annulated PBI, whereas S- and Se-annulated PBIs exhibited blue-shifted absorption spectra. Bay-annulation increased the HOMO and LUMO levels of the N-annulated perylene bisimide, whereas a slight increase in the LUMO level and a decrease in the HOMO levels were observed in the case of S- and Se-annulated perylene bisimides, in comparison to the simple perylene bisimide. The band gaps of PBI and PBI-N were almost same, whereas an increase in the band gaps were observed in the case of S- and Se-annulated PBIs. The tendency to freeze in the ordered glassy columnar phase for PBI-N and PBI-S will help to overcome the charge traps due to crystallization, which are detrimental to one-dimensional charge carrier mobility. These solution processable electron deficient columnar semiconductors possessing good thermal stability may form an easily accessible promising class of n-type materials.

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Section: Introductionmentioning

confidence: 91%

Columnar Self‐Assembly of Electron‐Deficient Dendronized Bay‐Annulated Perylene Bisimides

Gupta

Rao

Prasad

et al. 2018

Chemistry A European J

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“…[24][25][26] The use of perylene derivatives in OLEDs has been explored by several groups, however, most studies primarily focused on physicochemical properties of materials and their potential applications rather than device performance and characteristics. Hence, emitters were only incorporated in simple OLED structures which often required drive voltages >8 V and achieved a maximum luminance of mostly <1000 cd m −2 at voltages higher than 10 V, [27][28][29][30][31] similar to other studies of liquid crystal-based OLEDs. [17,[32][33][34][35] In order to develop more efficient liquid crystalline OLEDs, the knowledge about the self-assembling properties of DLCs that the community has acquired over the past decades needs to be appropriately integrated with state-of-the-art OLED structures and with the functional materials used in these.…”

Section: Introductionmentioning

confidence: 88%

Organic Light‐Emitting Diodes Based on a Columnar Liquid‐Crystalline Perylene Emitter

Keum

Becker

Archer

et al. 2020

Advanced Optical Materials

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Liquid crystalline materials possess great potential as emitters in organic light‐emitting diodes (OLEDs) due to their self‐assembling property, which may lead to anisotropic films and improved charge transport. Here, the key photophysical properties of the columnar liquid crystalline emitter perylene‐3,4,9,10‐tetracarboxylic tetraethyl ester (PTCTE) are investigated and the material is implemented into OLEDs. It is found that vacuum‐deposited PTCTE films exhibit preferential horizontal orientation of the transition dipole moment. Embedding the emitter into different host materials leads to increased photoluminescence quantum yield but reduces molecular orientation compared to the neat film. OLEDs containing PTCTE doped into an exciplex‐forming co‐host achieve very high luminance exceeding 10 000 cd m−2 at 5.7 V, which is among the best performances of OLEDs based on columnar liquid crystalline emitters reported so far.

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“…[7] Recently,w eh ave reportedt he electroluminescent behaviour of bay-annulated PE tetraesters as emissive layersi nO LEDs. [8] In general,t he optical and electronic properties of these derivatives are due to local p-p interactions of the PE chromophoret hat lead to molecular aggregation and thesea ggregations furtherp rovide means for efficient electron conduction within the aggregates. [9,10] Additionally,P Ed erivatives (bis-imides and tetraesters) show crystalline and LC phases because the flexibility of the cores is an important parameter for supramolecular self-assembly.…”

Section: Introductionmentioning

confidence: 99%

“…PE imides (mono‐ and di‐) have been used in bulk‐heterojunction solar cells, as well as orbital and colour tuning . Recently, we have reported the electroluminescent behaviour of bay‐annulated PE tetraesters as emissive layers in OLEDs . In general, the optical and electronic properties of these derivatives are due to local π–π interactions of the PE chromophore that lead to molecular aggregation and these aggregations further provide means for efficient electron conduction within the aggregates .…”

Section: Introductionmentioning

confidence: 99%

Room‐Temperature Columnar Nematic and Soft Crystalline Columnar Assemblies of a New Series of Perylene‐Centred Disc Tetramers

Bala

Gupta

et al. 2017

Chemistry A European J

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Three new oligomeric perylene (PE) tetraester derivatives, consisting of a PE-based core with four pentaalkynylbenzene units attached through flexible alkyl spacers, are reported. These derivatives were investigated for their mesomorphic properties and thermal, photophysical, and electrochemical behaviour. Small- (SAXS) and wide-angle X-ray scattering (WAXS) studies were performed to deduce the exact nature of the phases. To resolve overlapping reflections and facilitate their indexing, grazing-incidence SAXS/WAXS experiments were carried out on oriented thin films on indium tin oxide (ITO)-coated glass substrate. The corresponding electron density maps were derived from the intensities observed in the diffraction pattern. Whereas compounds with shorter alkyl spacers (n=6 and 8) were found to self-organise into soft crystalline columnar assemblies, those with longer spacers (n=10) exhibited a liquid-crystalline columnar nematic mesophase. This is in contrast to previous reports that describe highly symmetric 2D hexagonal and rectangular columnar structures of PE-based mesogens. The morphology of self-assembly was found to transform from soft crystal columnar to nematic columnar phase through simple variation in the number of alkyl spacers. All compounds exhibited excellent fluorescence emission properties with a very good quantum yield and large band gap. Apart from high solubility and good quantum yield, these compounds can serve as standards to measure quantum yields of unknown samples. These compounds also display green luminescence and may find applications for various optoelectronic devices.

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Electroluminescent room temperature columnar liquid crystals based on bay-annulated perylene tetraesters

Abstract: Room temperature columnar liquid crystals and their application in OLEDs.

Cited by 47 publications

References 48 publications

Columnar Self‐Assembly of Electron‐Deficient Dendronized Bay‐Annulated Perylene Bisimides

Columnar Self‐Assembly of Electron‐Deficient Dendronized Bay‐Annulated Perylene Bisimides

Organic Light‐Emitting Diodes Based on a Columnar Liquid‐Crystalline Perylene Emitter

Room‐Temperature Columnar Nematic and Soft Crystalline Columnar Assemblies of a New Series of Perylene‐Centred Disc Tetramers

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