Light‐Emitting Liquid Crystal Displays Based on an Aggregation‐Induced Emission Luminogen

Zhao, Dongyu; Fan, Fan; Cheng, Juan; Zhang, Yilin; Wong, K. S.; Chigrinov, Vladimir G.; Kwok, Hoi‐Sing; Guo, Lin; Tang, Benzhong

doi:10.1002/adom.201400428

Cited by 113 publications

(67 citation statements)

References 30 publications

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“…Nevertheless, as demonstrated deductively in this work, appropriate molecular designs such as the introduction of a phenyl ring suppress the nonradiative decays of HBT molecules, allowing sufficiently high Φ FL values in both aggregated (solid) and nonaggregated (LC mixtures) states. It had not been clarified so far whether the AIEE‐type fluorescent molecules were aggregated or dispersed in the LC hosts . Our experiments evidenced that HBT‐based ESIPT fluorescent molecules are molecularly dispersed in 5CB and their Φ FL values are not so decreased due to the appropriate molecular design.…”

Section: Resultsmentioning

confidence: 70%

“…Recently, several rod‐ and banana‐shaped fluorescent LCs have been used for polarized light emission . LC materials doped with AIEE dyes were also reported, aiming at the development of emissive LC displays or emergence of circularly polarized luminescence . Both types of the reports have not discussed in detail the energy dissipation processes via ESIPT or AIEE protocols in terms of molecular view.…”

Section: Introductionmentioning

confidence: 99%

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Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Zhang

Sakurai

Aotani

et al. 2018

Advanced Optical Materials

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solid-state emitters, electroluminescent devices, organic lasers, and so on. [1][2][3][4][5] Particularly, emission through excitedstate intramolecular proton transfer (ESIPT) mechanism with an extremely large Stokes shift [6][7][8][9] (anti-Kasha rule) suppresses excitation energy dissipation via self-absorption, providing attractive material platforms for optical device fabrication. [10,11] ESIPT is a photochemical process that produces a tautomer with a different electronic structure from the original excited form (Figure 1a). The requisite of chemical structures for ESIPT is the presence of an intramolecular hydrogen bond (H-bond) between the proton donor (OH and NH 2 ) and the proton acceptor (N and CO) groups close to one another in a single molecule. Recent notable reports on the ESIPT fluorophores include the polymorph-dependent emissive crystals, [12,13] double proton transfer process with an extra-large Stokes shift, [14] amplified spontaneous emission, [15][16][17] lasing system, [18][19][20] environment-sensitive multicolored materials, [21][22][23][24] and the use as emitters with electrically generated intramolecular proton transfers. [25] Most of ESIPT molecules show significant fluorescence in the solid states, not suffering from "concentration quenching" and thus serving as aggregation-induced emission enhancement (AIEE) materials. [26][27][28] The ESIPT process requires structural relaxations upon proton transfer, and thus a certain conformational freedom is allowed for the molecular structures. [29] The conformational freedom results in allowing the possible nonradiative pathways especially in solution (Figure 1b), giving AIEE characters to the ESIPT molecules. [30,31] The AIEE character is advantageous because light outputs from the systems are extremely high embedded into actual devices to avoid the concentration quenching. [32] However, most of the previous ESIPT as well as AIEE systems have been mostly reported in the rigid solid phase such as single crystals, polycrystals, or powders [11,12] -not in liquid crystals (LCs). Although columnar LCs with ESIPT-active cores were reported, [33,34] simple rod-shaped LC molecules embedded with ESIPT-active group have been limited. [35,36] In contrast to columnar and cubic liquid crystal phases with highly ordered structures, nematic as well as several smectic subphases can easily align macroscopically by rubbed surfaces, mechanical stimuli, and electric and magnetic fields. [37][38][39] Fluorescence via excited-state intramolecular proton transfer (ESIPT) provides strong light emission with a large Stokes shift and environment-sensitive unique spectral patterns. Particular systems including 2-(2-hydroxyphenyl) benzothiazole (HBT) serve as efficient solid-state emitters with the ESIPT mechanism and aggregation-induced emission enhancement (AIEE) property, but have not been used for liquid crystalline (LC) materials. Here, rod-shaped fluorescent LCs with ESIPT characters are newly developed based on the HBT motif. The design of the targeted mole...

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Section: Resultsmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Zhang

Sakurai

Aotani

et al. 2018

Advanced Optical Materials

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“…Intense absorption bands between 250 and 400 nm are observed for both compounds, which are attributed to the π-π electron transition of aromatic rings in the TPE core. 39 A very weak absorption band in the range of 400-525 nm is detected for TPE-PBN, probably it is assigned to the intramolecular charge transfer (ICT) process caused by the separated HOMO (highest occupied molecular orbitals) and LUMO…”

Section: Photophysical Propertymentioning

confidence: 99%

Highly efficient blueish-green fluorescent OLEDs based on AIE liquid crystal molecules: from ingenious molecular design to multifunction materials

et al. 2017

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ABSTRACT:In order to seek the balance point between liquid crystalline and high efficiency emission, two novel aggregation-induced emission-based (AIE) liquid crystal materials of TPE-PBN and TPE-2PBN, which contains tetraphenylethene derivative as the emission core and 4-cynobiphenyl moiety as the mesogenic unit, were designed and prepared. Both simple molecules showed a mesophase at high temperature evidenced by polarised optical microscopy (POM), differential scanning calorimetry (DSC) and temperature-dependent X-ray diffraction (XRD).Simultaneously, TPE-PBN and TPE-2PBN presented clearly AIE characteristics in the blueishgreen region and achieved the high emission quantum efficiency of 71% and 83% in solid state, respectively. Due to the self-assembly property of thermotropic liquid crystals, both compounds showed higher hole mobilities in the annealed films than in pristine films. Employing TPE-PBN and TPE-2PBN as the emitting materials, both non-doped devices and doped devices were fabricated. The TPE-PBN-based doped OLEDs showed a better device performance with an external quantum efficiency (EQE) of 4.1% which is among the highest EQE of the blue AIE fluorescent OLEDs.

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“…Liquid crystal displays (LCDs) are the mainstream display devices in our daily lives. LCDs occupy a large portion of the market share of panels, owing to several advantages, such as high screen resolutions, light weights, and thin profiles, which enable portable applications . However, the optical throughput of traditional LCD is still very low, and the imperfect “dark” state affects the quality of viewing.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Predesigned Ferroelectric Liquid Crystals and Their Applications in Field‐Sequential Color Displays

Zhang

Liu

Emelyanenko

et al. 2018

Adv Funct Materials

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A series of low transition temperature and fast response chiral smectic C (SmC*) liquid crystals is designed and synthesized. The phase transition behaviors and electrooptical properties of the synthesized compounds are investigated and compared with reported values. The ferroelectric phase of the liquid crystals is characterized by means of differential scanning calorimetry, polarizing optical microscopy, wide-angle X-ray scattering (WAXS), and electrooptical measurements. The wide SmC* phase is achieved via the induction of achiral trisiloxane and a chiral methyl-lateral substituent onto the terminuses of the molecules. The optimized packing arrangement model is studied based on the exceptionally high apparent tilt angles (≈41°) and smectic layer spacing observed using WAXS. A fast response time of 0.3 ms in an electric field of 10 V µm −1 provides an opportunity to use the synthesized materials for field-sequential color liquid crystal displays (FSCLCDs). An FSCLCD sample cell is fabricated using the synthesized ferroelectric liquid crystals via a red (R), green (G), and blue (B) backlight. A color-frame frequency of more than 500 Hz (i.e., a frame frequency more than 166 Hz) is achieved. As a single material liquid crystal display cell, the synthesized ferroelectric liquid crystals show great performances at room temperature.

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Light‐Emitting Liquid Crystal Displays Based on an Aggregation‐Induced Emission Luminogen

Cited by 113 publications

References 30 publications

Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Highly Fluorescent Liquid Crystals from Excited‐State Intramolecular Proton Transfer Molecules

Highly efficient blueish-green fluorescent OLEDs based on AIE liquid crystal molecules: from ingenious molecular design to multifunction materials

Synthesis of Predesigned Ferroelectric Liquid Crystals and Their Applications in Field‐Sequential Color Displays

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