Glassy Liquid Crystals as Self-Organized Films for Robust Optoelectronic Devices

Chen, H.-M. Philp; Ou, Jane J.; Chen, Shaw H.

doi:10.1007/978-3-319-04867-3_6

Cited by 15 publications

(10 citation statements)

References 56 publications

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“…As the neat TKHD, the SWCNTs/TKHD NCs can form a “glassy”-like columnar state that takes place in a large temperature range including the room temperatures (16–40 °C) . The practical importance of glassy DLC films for robust optoelectronic devices is well established . Notably, the glassy state of DLCs, which have a molecular structure of the type similar to that of TKHD, exhibits interesting luminescence behavior at room temperature .…”

Section: Introductionmentioning

confidence: 99%

“…31 The practical importance of glassy DLC films for robust optoelectronic devices is well established. 32 Notably, the glassy state of DLCs, which have a molecular structure of the type similar to that of TKHD, exhibits interesting luminescence behavior at room temperature. 27 In the present work, our research interest was focused on the photoresponse of glassy thin films of TKHD and TKHD filled with SWCNTs, especially on the photo-induced changes of their photoluminescence (PL) that are relevant for optoelectronic applications at ambient temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Photoluminescent Thin Films of Room-Temperature Glassy Tris(keto-hydrozone) Discotic Liquid Crystals and Their Nanocomposites with Single-Walled Carbon Nanotubes for Optoelectronics

Hadjichristov

Marinov

2023

ACS Omega

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This study addresses the photoresponse of liquid-crystalline tris(keto-hydrozone) discotic (TKHD)a star-shaped molecular structure with three branches. Object of our research interest was also TKHD filled with single-walled carbon nanotubes (SWCNTs) at a concentration of 1 wt %. At room temperature, the discotic liquid crystals in thin films (thickness 3 μm) of both TKHD and nanocomposite SWCNT/TKHD were in a glassy state. Such glassy thin films exhibited photoluminescence ranging from the deep-red to the near-infrared spectral region, being attractive for organic optoelectronics. The addition of SWCNTs to TKHD was found to stabilize the photoluminescence of TKHD, which is of significance for optoelectronic device applications. The photothermoelectrical response of highly conductive SWCNT/TKHD nanocomposite films was characterized by electrical impedance spectroscopy in the frequency range from 1 Hz to 1 MHz of the applied electric field. It was elucidated that the reversible photothermoelectrical effect in SWCNT/TKHD films occurs through SWCNTs and their network.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photoluminescent Thin Films of Room-Temperature Glassy Tris(keto-hydrozone) Discotic Liquid Crystals and Their Nanocomposites with Single-Walled Carbon Nanotubes for Optoelectronics

Hadjichristov

Marinov

2023

ACS Omega

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“…Over the past several decades, the design and synthesis of glass-forming ChGLCs have evolved, resulting in improved morphological stability and more tailorable optical properties. 3,11,12 Conventional ChGLCs derived from oligomer or siloxane backbones were first established in the 1990s. 13,14 Since then, these materials have been engineered to achieve reflective color at desired wavelengths by formulating the mesogenic molar ratio to have a targeted twisting power or by quenching the desired helical pitch length into the glassy state from various melt temperatures.…”

Section: Introductionmentioning

confidence: 99%

“…18 Core-pendent type GLCs represent a distinct design approach that has been shown to achieve significantly higher glass transition and clearing temperatures. 3 Rod-like pendents are attached to a volume-excluding core via flexible linkages, which creates a balance between the mesogenic order and the steric hindrance, resulting in a kinetic barrier to crystallization and improved morphological stability. Glassy films of optimized core-pendent ChGLCs have been reported with glass transitions and clearing points up to 130 and 350 °C, respectively, and sample films have survived in the absence of crystallization for two decades and counting.…”

Section: Introductionmentioning

confidence: 99%

High-Temperature Enantiomeric Glassy Liquid Crystals with Exclusive Cholesteric Mesomorphism

Carlson,

Chen,

Baur

et al. 2023

ACS Appl. Opt. Mater.

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Glassy liquid crystals are a unique class of materials that can preserve their spontaneously ordered liquid crystalline state upon cooling through the glass-transition temperature. Cholesteric glassy liquid crystals (ChGLCs), in particular, are attractive for their selective reflection and circular polarization properties, and core-pendent ChGLCs display high morphological stability and exclusive mesomorphism over a broad temperature range. An enantiomeric pair of core-pendent ChGLCs was prepared following a deterministic synthesis route, allowing for both enantiomers to be scaled up and purified at the gram-level. The ability to process these compounds into well-ordered, nm- and μm-thick films with glassy, monodomain cholesteric structures is demonstrated. Processed films exhibit a photonic band gap structure that splits unpolarized incident light into circularly polarized transmitted light of one handedness and circularly polarized reflected light of the opposite handedness. Mixing enantiomers at different stoichiometric ratios alters the cholesteric structure, thereby tuning the wavelength of reflection from the near-UV to the mid-IR. Moreover, glass transition temperatures and clearing temperatures of enantiomeric mixtures are independent of the mixing ratio, enabling the design and fabrication of durable circular polarizers, notch filters, and polarization control devices across different spectral regions.

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“…Physical vapor deposition (PVD) can synthesize stable glassy phases of many materials, − but for organic molecules, PVD can prepare a more unusual material: glasses in which the molecules show overall orientational ordering . This anisotropy in structure causes anisotropy in optical, mechanical, and electronic properties, making the films potentially useful for organic electronics . Discotic mesogens are attractive for applications in organic electronic devices, as they can show columnar ordering via π–π stacking of molecules, one-dimensional charge mobility, and alignment relative to the substrate that can be tailored for various applications .…”

mentioning

confidence: 99%

Using 4D STEM to Probe Mesoscale Order in Molecular Glass Films Prepared by Physical Vapor Deposition

Chatterjee

Huang

et al. 2023

Nano Lett.

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Physical vapor deposition can be used to prepare highly stable organic glass systems where the molecules show orientational and translational ordering at the nanoscale. We have used low-dose four-dimensional scanning transmission electron microscopy (4D STEM), enabled by a fast direct electron detector, to map columnar order in glassy samples of a discotic mesogen using a 2 nm probe. Both vapor-deposited and liquid-cooled glassy films show domains of similar orientation, but their size varies from tens to hundreds of nanometers, depending on processing. Domain sizes are consistent with surface-diffusion-mediated ordering during film deposition. These results demonstrate the ability of low-dose 4D STEM to characterize a mesoscale structure in a molecular glass system which may be relevant to organic electronics.

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Glassy Liquid Crystals as Self-Organized Films for Robust Optoelectronic Devices

Cited by 15 publications

References 56 publications

Photoluminescent Thin Films of Room-Temperature Glassy Tris(keto-hydrozone) Discotic Liquid Crystals and Their Nanocomposites with Single-Walled Carbon Nanotubes for Optoelectronics

Photoluminescent Thin Films of Room-Temperature Glassy Tris(keto-hydrozone) Discotic Liquid Crystals and Their Nanocomposites with Single-Walled Carbon Nanotubes for Optoelectronics

High-Temperature Enantiomeric Glassy Liquid Crystals with Exclusive Cholesteric Mesomorphism

Using 4D STEM to Probe Mesoscale Order in Molecular Glass Films Prepared by Physical Vapor Deposition

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