Browsing by Author "Wu, San-Lien"

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Conformational Preferences and the Phase Stability of Fullerene Hexa-adducts
(2016-07-20)
Wu, San-Lien
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Hong, Chen-Yang
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Wu, Kuan-Yi
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Lan, Shih-Ting
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Hsieh, Chou-Ting
Molecular conformation and the assembly structure determine the spatial arrangements of the constituent units and the functions of a molecule. Although, fullerene hexa-adducts (FHAs) have been known as functional materials with great versatility, their conformational preferences and phase stability remain a complicate issue. By choosing bithiophene (T-2) and dodecyl bithiophene (C12T2) as the peripheral units of FHA, and using microscopic, scattering and diffraction characterizations, our study reveals how the intramolecular interaction and environmental stimulus affects the conformational preferences and phase stability of FHAs.
Flat-on ambipolar triphenylamine/C-60 nano-stacks formed from the self-organization of a pyramid-sphere-shaped amphiphile
(2016-01-01)
Liang, Wei-Wei
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Huang, Chi-Feng
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Wu, Kuan-Yi
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Wu, San-Lien
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Chang, Shu-Ting
A giant amphiphile, which is constructed with an amorphous nano-pyramid (triphenylamine, TPA) and a crystalline nano-sphere (C-60), was synthesized. Structural characterization indicates that this pyramid-sphere-shaped amphiphile (TPA-C-60) forms a solvent-induced ordered phase, in which the two constituent units self-assemble into alternating stacks of two-dimensional (2D) TPA and C-60 nanosheets. Due to the complexity of the molecular structure and the amorphous nature of the nano-pyramid, phase formation was driven by intermolecular C-60-C-60 interactions and the ordered phase could not be reformed from the TPA-C-60 melt. Oriented crystal arrays of TPA-C-60, which contain flaton TPA/C-60 nano-stacks, can be obtained via a PDMS-assisted crystallization (PAC) technique. The flaton dual-channel supramolecular structure of TPA-C-60 delivered ambipolar and balanced charge-transport characteristics with an average me of 2.11 x 10(-4) cm(2) V-1 s(-1) and mh of 3.37 x 10(-4) cm(2) V-1 s(-1). The anisotropic charge-transport ability of the pyramid-sphere-shaped amphiphile was further understood based on the lattice structure and the lattice orientation of TPA-C-60 revealed from electron diffraction analyses.
Highly-integrated, laser manipulable aqueous metal carbonyl vesicles (MCsomes) with aggregation-induced emission (AIE) and aggregation-enhanced IR absorption (AEIRA)
(2016)
Murshid, Nimer
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Yuyama, Ken-ichi
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Wu, San-Lien
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Wu, Kuan-Yi
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Masuhara, Hiroshi
A highly-integrated, laser manipulable multi-functional metal carbonyl nanovesicle (MCsome) with aggregation-induced emission (AIE) and aggregation-enhanced IR absorption (AEIRA) is created via the self-assembly of a bithiophene tethered-Fp acyl derivative (Fp: CpFe(CO)(2)) (1). Although 1 is hydrophobic and non-surface-active, the molecule can self-assemble in water into vesicles without detectable critical aggregation concentration (CAC). The water-carbonyl interaction (WCI) is responsible for the colloidal stability. The bilayer membrane structure with the bithiophene moieties associated within the inner wall and the iron-carbonyl units exposed to water is confirmed by transmission electron microscopy (TEM), atomic force microscopy (AFM), and cyclic voltammetry (CV) experiments. The synchrotron small-angle X-ray scattering (SAXS) experiment suggests that the bithiophene groups are interdigitated within the membrane. The spatial segregation of the AIE-active bithiophene domain from the iron-carbonyl units by the butanoyl spacers prevents the quenching effect of the iron and renders the MCsome photoluminescent. The polarizable iron-carbonyl groups on the surface of the MCsome create an enhanced optical field upon infrared (IR) irradiation, resulting in an enhancement (ca. 100-fold) in IR absorption for the carbonyl groups as compared to the same concentration of molecule 1 in THF. When the MCsome interacts with a focused continuous-wave near-IR (NIR) laser beam, a strong gradient (trapping) force is generated allowing the laser trapping of the MCsome without using additives. A sharp contrast in the refractive index (RI) of 1 (RI = 1.71) with water (RI = 1.33) accounts for this laser manipulability that is difficult to be achieved for nanosized liposomes (RI = 1.46). As illustrated, the MCsome of 1 represents a novel group of vesicular colloids, which is amenable to functional materials complementary to extensively studied liposomes and polymersomes.
Influences of Conjugation Length on Organic Field-Effect Transistor Performances and Thin Film Structures of Diketopyrrolopyrrole-Oligomers
(2018-03-14)
Huang, Yi-Fan
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Chang, Shu-Ting
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Wu, Kuan-Yi
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Wu, San-Lien
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Ciou, Guan-Ting
Here, two diketopyrrolopyrrole (DPP)-based oligomers, DPP-4T and DPP-6T, are studied to reveal the influences of conjugation length on thin-film morphology and organic field-effect transistor (OFET) performances. PDMS-assisted crystallization in a solvent-annealing chamber is applied to prepare crystal arrays of DPP-4T and DPP-6T to optimize the quality of charge channels for OFET characterizations. To deliver insights into microstructure and morphology of thin films, a characterization procedure for determining molecular packing in thin film and crystallinity of the crystal arrays is presented via grazing incidence wide-angle X-ray scattering, electron diffraction, and lattice simulation software package (Cerius2). With the lattice parameters derived from analyses of grazing incidence wide-angle X-ray scattering (GIWAXS) and electron diffraction (ED), the lattice modeling results indicate that the inferior organic field-effect transistor (OFET) performances of DPP-6T are attributed to longer pi-stacking distance. Also, less-ordered molecular arrangement and lower continuity of crystalline domains, both of which are revealed from crystallinity results, lead to lower mobility of DPP-6T. In this case, longer conjugated backbones with more conformational degrees of freedom thus cause inherent crystal defects during the crystal growth process, despite the potential to enhance intermolecular pi-orbital overlap. Therefore, to achieve better OFET performance, suitable backbone length makes conjugated oligomers give high intermolecular pi-orbital overlap and low density of structural disorder, which are the priorities for constructing good charge channel.
n-Type Thin-Film Transistors Based on Diketopyrrolopyrrole Derivatives: Role of Siloxane Side Chains and Electron-Withdrawing Substituents
(2020-01-08)
Prakoso, Suhendro Purbo
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Kumar, Sushil
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Wu, San-Lien
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Ciou, Guan-Ting
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Ke, Yao-Jin
The physical properties, packing, morphology, and semiconducting performance of a planar pi-conjugated system can be effectively modified by introducing side chains and substituent groups, both of which can be complementary to the pi framework in changing the intermolecular association, frontier molecular orbital energy, optical band gap, and others. We herein show that installation of end-capped electron-withdrawing groups (EWGs), such as dicyanovinyl (-DCV), 3-ethylrhodanine (-RD), and 2-(3-oxo-indan-1-ylidene)-malononitrile (-INCN), together with siloxane side chains to the backbones of dithienyldiketopyrrolopyrrole (DPPT), such as DPPT-Si-DCV, DPPT-Si-RD, and DPPT-Si-INCN, can greatly improve its solubility, air stability, and film morphology to serve as an n-channel in thin-film transistor fabrication. The EWGs attached to the DPPT core narrowed the optical band gap (E-g(opt)) and changed the highest occupied molecular orbital and the lowest unoccupied molecular orbital energies (E-HOMO and E-LUMO), making them suitable for n-channel field-effect transistor (FET) applications. The benefits of introducing siloxane side chains to the DPPT core include enhanced solubility, low crystallization barrier, enantiotropic phase behavior, and much improved FET performance. The DPPT-Si-INCN film displayed low-lying HOMO (-5.82 eV) and LUMO (-4.60 eV) energy levels and an optical band gap as low as 1.22 eV, all of which suggest that this derivative can be quite resistant toward aerial oxidation. Thin films of these derivatives were prepared by the solution-shear method. A comparison of the solution-sheared films indicated that the molecular packing motif of DPPT-Si-INCN film was somehow different from that of DPPT-Si-DCV and DPPT-Si-RD, in which the pi-pi stacking tended to align orthogonally to the shearing direction. This specific pi-pi stacking alignment could have an impact on the electron mobility (mu(e)) values in transistors based on the solution-sheared films.
Packing Principles for Donor-Acceptor Oligomers from Analysis of Single Crystals
(2016-08-09)
Huang, Chi-Feng
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Wu, San-Lien
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Huang, Yi-Fan
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Chen, Ying-Chen
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Chang, Shu-Ting
D-A conjugated molecules are complicated in both their molecular and their packing structures. In this perspective, we summarize more than 40 crystal lattices of conjugated oligomers to identify the morphological influence of each building block on the D-A molecules. These lattice structures reveal not only the packing preferences of the conjugated oligomers but also the conformational disorder in the lattices. The presence of this disorder in slowly grown crystals implies that attaining total long-range conformational order is challenging for D-A oligomers, which are structurally complicated and readily distorted and which have building blocks of incommensurate packing dimensions. In optoelectronic applications, a decreased duration of processing can prevent ordering and trap the thin films of D-A oligomers from becoming crystalline phases. Although D-A oligomers conform to packing principles in the formation of a single crystal, their phase behaviors in the formation of active thin films are much more difficult to comprehend. Continuous advances in methods of characterization are still strongly required for the steps of attaining a true structure property relation of D-A oligomers in active films for optoelectronic applications.
Roles of 3-Ethylrhodanine in Attaining Highly Ordered Crystal Arrays of Ambipolar Diketopyrrolopyrrole Oligomers
(2017-05-03)
Wu, San-Lien
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Huang, Yi-Fan
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Hsieh, Chou-Ting
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Lai, Bo-Han
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Tseng, Po-Sen
Until now, only limited DPP oligomers delivered ambipolar semiconductor characteristics. To develop a facile strategy of preparing ambipolar mono-DPP oligomers, two dithienyl diketopyrrolopyrrole (DPPT) based-conjugated molecules, DPPT-RD and DPPT-DCV, which contain 3-ethylrhodanine (RD) and dicyano-2-vinyl (DCV) end substituents were synthesized. The influences of the -RD end substituents on the molecular properties, solid-state morphology, and OFET performances of the DPPT oligomer were investigated. The UV-vis absorption and CV results showed that the RD end substituents provide the DPPT oligomer suitable EHOMO and ELUMO for hole and electron injection from the Au source-drain electrodes. Moreover, the RD end substituents also improve the crystalline nature of the DPPT oligomer. That is, DPPT-RD can form crystal arrays with good lattice orientation, larger crystalline size, and without polymorphism. With those properties, DPPT-RD thus display ambipolar characteristic with mu(h) and mu(e) reaching 2.16 x 10(-2) and 7.27 x 10(-2) cm2 V-1 s(-1), respectively.
Self-Assembly Behavior of Dendritic Liquid Crystals and its Implications in the Packing Structure of Functional Molecular Nanoparticles
(2018-03-01)
Wang, Chien-Lung
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Prakoso, Suhendro Purbo
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Wu, San-Lien
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應用化學系
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Department of Applied Chemistry
In this mini-review, the self-assembly characteristics of dendritic liquid crystals (LCs) are summarized. By studying and comparing the mesomorphic behavior of dendritic LCs with various core units and peripheral mesogenic units, their packing principle is established. It is found that the chirality, connecting position, and curvature of the peripheral mesogenic units play significant roles in the resulting self-assembly structures of dendritic LCs, whereas the core symmetry and strength of intramolecular interaction affect the geometry and conformational preferences of the dendritic LCs. This fundamental knowledge gives useful guidelines to predict the self-assembly behaviors of novel functional molecular nanoparticles, which share very similar molecular architecture with dendritic LCs.
Stepwise Structural Evolution of a DTS-F2BT Oligomer and Influence of Structural Disorder on Organic Field Effect Transistors and Organic Photovoltaic Performance
(2016-12-27)
Huang, Chi-Feng
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Huang, Sin-Hong
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Hsieh, Chou-Ting
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Chao, Yi-Hsiang
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Li, Chia-Hua
An A-D-A oligomer, DTS(F2BT)(2), was synthesized; its structural evolution was studied with DSC, POM, 2D-WAXD, and in-situ GI-XRD. The structural evolution of DTS(F2BT)(2) is stepwise and kinetically slow. Both rapid drying and the presence of PC71BM trapped DTS(F2BT)(2) in a less ordered nematic (N) phase. PDMS-assisted crystallization enabled a pristine DTS(F2BT)(2) thin film to attain a more ordered equilibrium phase, and enhanced the OFET mobility of DTS(F2BT)(2). In OPV devices, DIO additive drove the DTS(F2BT)(2) domains in the DTS(F2BT)(2):PC71BM blended film from the N phase toward the equilibrium phase, and resulted in enhanced OPV performances. These results reveal the slow ordering process of the A-D-A oligomer, and the importance of monitoring the degree of structural evolution of the active thin films in organic optoelectronics.