Patterning of Discotic Liquid Crystals with Tunable Molecular Orientation for Electronic Applications

Zou, Cheng; Wang, Jingxia; Wang, Meng; Wu, Yuchen; Gu, Kehua; Shen, Zhihao; Xiong, Guirong; Yang, Huai; Jiang, Lei; Ikeda, Tomiki

doi:10.1002/smll.201800557

Cited by 33 publications

(33 citation statements)

References 56 publications

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“…Such discotic liquid crystals (DLCs) may exhibit semiconducting properties, with promising applications in the photovoltaic industry. 5 They are also effective as lubricants, outperforming hydrocarbons in some conditions. 6 In all these practical settings, an understanding of LCs at surfaces and interfaces is paramount, which combined with sheer curiosity, has spawned a number of theoretical, computational, and experimental studies.…”

Section: Introductionmentioning

confidence: 99%

Ordering of Oblate Hard Particles between Hybrid Penetrable Walls

2020

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We report a Monte Carlo (MC) simulation study of a model discotic liquid crystal (DLC) confined between hybrid walls with controllable penetrability. The model consists of oblate hard Gaussian overlap (HGO) particles. Particle–substrate interactions are modeled as follows: each substrate sees a particle as a disc of zero thickness and diameter D less than or equal to that of the actual particle, σ 0 , embedded inside the particle and located halfway along, and perpendicular to, its minor axis. This allows us to control the anchoring properties of the substrates, from planar (edge-on) for D ≈ 0 to homeotropic (face-on) for D ≈ σ 0 , which can be done independently at either substrate. Depending on the values of D s ≡ D /σ 0 at the top ( D s t ) and bottom ( D s b ) substrates, we find domains in ( D s b , D s t ) space in which particle alignment is uniform planar (UP), is uniform homeotropic (UH), or varies linearly from planar at one substrate to homeotropic at the other (Lin). These domains are separated by regions of bistability (P–Lin and H–Lin), which appear to be wider than for prolate HGOs, and there may be also a small tristable (P–H–Lin) region. Results are compared with the predictions of density functional theory, implemented at the level of Onsager’s second-virial approximation with Parsons-Lee rescaling. As in the case of symmetric confinement studied previously, the agreement between theory and simulation is substantially less good than for prolate HGOs: in particular, for the investigated substrate separation L = 6σ 0 , the Lin configuration is never predicted. These discrepancies are likely a consequence of the fact that Onsager’s theory is less accurate for discs than for rods.

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Section: Introductionmentioning

confidence: 99%

Ordering of Oblate Hard Particles between Hybrid Penetrable Walls

2020

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“…In our former work, we have revealed that molecular structure, anchoring effect, and surface energy play primary roles on the LC alignment . It is confirmed that non‐centrosymmetrical LC molecules prefer planar orientation with backbones perpendicular to the aligned microstripes, which also could be conversely tested and verified by 8‐TTP‐8.…”

Section: Resultsmentioning

confidence: 56%

“…First, 8‐TTP‐8 (1) whose molecular structure is shown in Figure g was used as a typical smectic LC to fabricate well‐aligned microstripe arrays at 25 °C. The aligned ω,ω′‐terthiophene microstripes were prepared in a sandwich system by a dewetting method similar with our former work …”

Section: Resultsmentioning

confidence: 99%

Patterning Smectic Liquid Crystals for OFETs at Low Temperature

Zou

Yanahashi

et al. 2019

Adv Funct Materials

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The preparation of regular microstructures with liquid crystalline materials for organic field effect transistors (OFETs) is an attractive but challenging issue. However, it is usually limited by the difficulty of forming large-area single crystals aligned in a desirable direction. Herein, several terthiophene (TTP) smectic liquid crystals such as 8-TTP-8 and 12-TTP-11OH are patterned into highly crystalline microstripes by a sandwich system through a dewetting method. Morphology and orientation of the microstripes strongly depend on preparation temperature. Microstripes prepared below crystalline temperature are uniform, well-ordered, and show high field effect transistor (FET) mobility. Meanwhile, π-π stacking direction of the TTP backbone is perpendicular to the microstripe and the molecules stack in layer structure, standing up on the SiO 2 /Si substrate, which would provide an effective pathway for p-type charge transport. However, higher preparation temperatures at liquid crystalline or isotropic liquid range induce many defects in the crystal formation process and cause incline of the unit cell, thus leading to a sharp decrease in FET mobility. A possible mechanism of molecular stacking at different temperature range is proposed. This strategy promised to provide a new opportunity for the high cost-efficiency fabrication of OFETs.

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“…Thus, it would pave the way for high-performance optoelectronic applications because of their remarkable anisotropic properties. 22,23,[35][36][37] Variant temperature XRD experiments were then utilized to confirm the presence of LC mesophases for all the hydrogenbonded supramolecular discotic TIB-A n complexes ( Fig. S16-S19, ESI †), with the typical diffraction patterns presented in Fig.…”

Section: Resultsmentioning

confidence: 99%