Browsing by Author "Huang, Yi-Fan"

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A high-performance lithium-ion capacitor with carbonized NiCo2O4 anode and vertically-aligned carbon nanoflakes cathode
(2019-11-01)
Cheng, Chung-Fu
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Li, Xiang
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Liu, Kewei
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Zou, Feng
;
Tung, Wei-Yao
Lithium ion capacitors (LICs) are energy storage devices integrating the complementary features of both supercapacitors and lithium ion batteries to simultaneously reach high energy and power densities. One of the major challenges in LIC technology is the kinetic imbalance between the faradaic insertion anode and capacitive cathode. Therefore, the design of electrode materials is crucial to enhance the rate performance of anode and the capacitance of the cathode in LIC devices. In this work, novel LICs were demonstrated with nanostructured cathode and anode. A vertically-aligned carbon nanoflakes (VACNFs) cathode provided high electrochemically active surface area and excellent conductivity, while a metal organic framework (MOF) derived carbonized nickel cobalt oxide (cNiCo(2)O(4)) anode ensured fast conversion reactions and remarkable cyclability. Electrochemical characterization of individual electrode confirmed that both electrodes exhibited good electron and ion transport capability. The LICs were fabricated with optimized electrode active materials loading to deliver high energy densities at desired charge/discharge rates. The devices exhibited energy density up to 136.9W h/kg (at 200 W/ kg). At higher power density of 40 kW/kg, under which a full charge-discharge can be finished within 4 s, the LICs could still deliver an energy density of 26.44W h/kg. The devices also showed a good cycle stability (approximate to 90% capacitance retention after 9000 cycles, under current density of 4 A/g) within the voltage range of 1-4.2 V.
Chemical mimicry of viral capsid self-assembly via corannulene-based pentatopic tectons
(2019-08-01)
Chen, Yu-Sheng
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Solel, Ephrath
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Huang, Yi-Fan
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Wang, Chien-Lung
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Tu, Tsung-Han
Self-assembly of twelve pentatopic tectons, which have complementary edges or can be linked using either digonal or trigonal connectors, represents the optimal synthetic strategy to achieve spherical objects, such as chemical capsids. This process requires conditions that secure uninterrupted equilibria of binding and self-correction en route to the global energy minimum. Here we report the synthesis of a highly soluble, deca-heterosubstituted corannulene that bears five terpyridine ligands. Spontaneous self-assembly of twelve such tectons with 30 cadmium(II) cations produces a giant icosahedral capsid as a thermodynamically stable single product in high yield. Nuclear magnetic resonance (NMR) methods, mass spectrometry analyses, small-angle X-ray scattering, transmission electron microscopy, and atomic force microscopy indicate that this spherical capsid has an external diameter of nearly 6 nm and shell thickness of 1 nm, in agreement with molecular modeling. NMR and liquid chromatography evidences imply that chiral self-sorting complexation generates a racemic mixture of homochiral capsids.
Cylindrical micelles of a POSS amphiphilic dendrimer as nano-reactors for polymerization
(2018-02-21)
Weng, Jing-Ting
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Yeh, Tso-Fan
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Samuel, Ashok Zachariah
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Huang, Yi-Fan
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Sie, Jyun-Hao
A low generation amphiphilic dendrimer, POSS-AD, which has a POSS core and eight amphiphilic arms, was synthesized and used as a nano-reactor to produce well-defined polymer nano-cylinders. Confirmed by small-angle X-ray scattering (SAXS), Raman and NMR spectrometry, monodispersed cylindrical micelles that contain a hydrophilic cavity with a diameter of 2.09 nm and a length of 4.26 nm were produced via co-assembling POSS-AD with hydrophilic liquids, such as H2O and HEMA in hydrophobic solvents. Taking the HEMA/POSS-AD cylindrical micelles as nano-reactors, polymerization of HEMA within the micelles results in polymer nano-cylinders (POSS-AD NPs) with a diameter of 2.24 nm and a length of 5.02 nm. The study confirmed that despite the inability to maintain specific shape in solution, low generation dendrimers form well-defined nano-containers or nano-reactors, which relies on co-assembling with hydrophilic guest molecules. These nano-reactors are robust enough to maintain their shape during the polymerization of the guest molecules. Polymer nano-cylinders with dimensions less than 10 nm can thus be produced from the HEMA/POSS-AD micelles. Since the chemical structure of low-generation dendrimers and the contents of the co-assembled nano-reactors can be easily adjusted, the concept holds the potential for the further developments of low-generation amphiphilic dendrimers.
Hydrogen Bonding-Induced H-Aggregation for Fluorescence Turn-On of the GFP Chromophore: Supramolecular Structural Rigidity
(1970-01-01)
Tsai, Meng-Shiue
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Tsai, Sung-Yu
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Huang, Yi-Fan
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Wang, Chien-Lung
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Sun, Shih-Sheng
To turn on the fluorescence of the native green fluorescence protein (GFP) chromophore, 4-hydroxybenzylidene-dimethylimidazolinone (HBDI), in an artificial supramolecular system has been a challenging task, because it requires high local environmental rigidity. This work shows that the formation of H-aggregates of an HBDI-containing organogelator results in two orders of magnitude fluorescence enhancement (phi(f)=2.9 vs. 0.02 %), in which the inter-HBDI OH...OH H-bonds play a crucial role. The aggregation-induced fluorescence enhancement of HBDI has important implications on the origin of the high fluorescence quantum efficiency of HBDI in the GFP beta-barrel and on the supramolecular strategy for a full fluorescence recovery of HBDI. These results reveal a new approach to designing rigid chromophore aggregates for high-performance optoelectronic properties.
Improved broadband and quasi-omnidirectional anti-reflection properties with biomimetic silicon nanostructures
(2007-12-01)
Huang, Yi-Fan
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Chattopadhyay, Surojit
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Jen, Yi-Jun
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Peng, Cheng-Yu
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Liu, Tze-An
Nature routinely produces nanostructured surfaces with useful properties, such as the self-cleaning lotus leaf, the colour of the butterfly wing, the photoreceptor in brittlestar and the anti-reflection observed in the moth eye. Scientists and engineers have been able to mimic some of these natural structures in the laboratory and in real-world applications. Here, we report a simple aperiodic array of silicon nanotips on a 6-inch wafer with a sub-wavelength structure that can suppress the reflection of light at a range of wavelengths from the ultraviolet, through the visible part of the spectrum, to the terahertz region. Reflection is suppressed for a wide range of angles of incidence and for both s- and p-polarized light. The antireflection properties of the silicon result from changes in the refractive index caused by variations in the height of the silicon nanotips, and can be simulated with models that have been used to explain the low reflection from moth eyes. The improved anti-reflection properties of the surfaces could have applications in renewable energy and electro-optical devices for the military.
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.
Influences of Out-Of-Plane Lattice Alignment on the OFET Performance of TIPS-PEN Crystal Arrays
(2016-11)
Wu, Kuan-Yi
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Hsieh, Chou-Ting
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Wang, Liang-Hsun
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Hsu, Chih-Hao
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Chang, Shu-Ting
In organic field-effect transistors (OFETs), the quality of charge transport pathway, controlled by crystal structures of organic semiconductors (OSCs), strongly affects the performance of the device. To achieve higher charge mobility, solution-processed single-crystal (SPSC) techniques have been used to decrease crystal defects by aligning the crystals of OSCs in the in-plane direction. Nonetheless, through SPSC techniques, whether the crystalline lattices are well aligned in the out-of-plane direction and how the out-of-plane lattice misorientaion affects OFET performances remain unclear. Here, a characterization protocol based on polarized optical microscope, X-ray diffraction, and electron diffraction is established to identify the lattice structure, the in-plane and out-of-plane lattice alignment in the crystal array of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-PEN). Regardless of the solvents used in the PDMS-assisted crystallization, the characterization protocol confirms that all the crystal arrays share the same lattice structure (form I phase), and have similar in-plane lattice alignment. However, TIPS-PEN molecules have sufficient time to unify their out-of-plane orientation and prevent the formation of low angle grain boundary (LAGB) during crystal growth if high boiling temperature solvents are used. The improved out-of-plane lattice alignment increases the hole mobility and decreases the performance fluctuations of devices. The results confirm that the out-of-plane lattice alignment significantly impacts the performance of the devices and the reproducibility of the solution-processed TIPS-PEN OFETs.
Influences of Structural Modification of S,N-Hexacenes on the Morphology and OFET Characteristics
(2019-06-19)
Huang, Yi-Fan
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Wang, Chun-Kai
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Lai, Bo-Han
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Chung, Chin-Lung
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Chen, Chin-Yi
Although chemical modifications on conjugated molecules are widely applied for the purpose of improving processability and device performances, the effect of the modification was far less investigated. Here, five S,N-hexacenes are studied to reveal the influences of (1) the lateral alkyl chain, (2) the terminal group (thiophene vs benzene), and (3) the end capping phenyl group of the hexacenes on the morphology and organic field-effect transistor (OFET) performances. Crystal arrays of the hexacenes were prepared via polydimethylsiloxane (PDMS)-assisted crystallization (PAC) prior to morphological and OFET characterizations. The lattice structures and crystal quality of the hexacenes were evaluated by microscopy and diffraction techniques including single-crystal diffractometer, electron diffraction, and grazing incidence wide-angle X-ray scattering. The systematic analyses led to the following conclusions: (1) the bulkier alkyl side chain assists to form more densely packed crystals with less structural defects; (2) the terminal thiophene rings bring about higher-lying E-HOMO, more ordered phase, and crystal orientation, whereas the terminal benzene rings deteriorate the structural order of the active layer and result in the liquid crystal phase; and (3) the phenyl end caps ameliorate the morphological order, intermolecular overlapping, thermal stability and elevate E-HOMO. Thus, EH-DTPTt-Ph delivers the highest mu(h), contributing to high-lying E-HOMO, well-oriented crystal array with a longer correlation length, and suitable lattice orientation. This systematic research provides the aspects about the effects of the functionalized S,N-hexacenes on the morphology and OFET characteristics, which is anticipated to be useful for the molecular design of heteroacenes.
Investigation of hydrogen-bonding mediated molecular packing of diketopyrrolopyrrole based donor-acceptor oligomers in the solid state
(2019-01-03)
Yang, Kun
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Li, Xiang
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Huang, Yi-Fan
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Bhatta, Ram S.
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Liu, Jiawei
Two diketopyrrolopyrrole (DPP)-based donor-acceptor oligomers with thermal labile 2-methylhexyl-2-oxylcarbonyl (mHoc) groups, mHocPBT and mHocTBT, were synthesized and characterized to study the hydrogenbonding mediated molecular packing in solid state. The soluble oligomers can be converted to strong intermolecular hydrogen-bonded and pigment-like materials HPBT and HTBT by annealing the casted solid film at a temperature between 180 and 200 degrees C. The formation of intermolecular hydrogen bonding significantly altered the conformation of the molecules, molecular packing structure and related optical properties of the oligomers, with HPBT molecule exhibiting bathochromic shift and HTBT molecule exhibiting hypsochromic shift on UV/Vis spectra. Spin-casted mHocTBT and HTBT films also exhibited interesting morphology and charge transport properties. Even though the single mHocTBT oligomer molecule has a better coplanar molecular conformation as compared with that of HTBT, an enhanced pi-pi stacking structure and larger crystal grain size rendered HTBT film better charge transport performance.
Li-Ion Capacitor Integrated with Nano-network-Structured Ni/NiO/C Anode and Nitrogen-Doped Carbonized Metal-Organic Framework Cathode with High Power and Long Cyclability
(2019-08-28)
Cheng, Chung-Fu
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Chen, Yu-Ming
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Zou, Feng
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Liu, Kewei
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Xia, Yanfeng
Lithium-ion capacitors (LICs) represent a new type of energy-storage devices, which have combined merits of high energy density Li-ion battery and high power density supercapacitor. Nevertheless, one significant challenge for LICs is the imbalanced kinetics between the fast capacitive cathode and relatively slow intercalation anode that limit the energy-storage performance. Here, the asymmetric LIC devices were developed based on a nitrogen-doped, carbonized zeolitic imidazolate framework (ZIF-8) cathode and a three-dimensional, nano-network-structured, conversion reaction-based Ni/NiO/C anode. These nanostructures associated with both the cathode and anode enable rapid electron and ions transport in the LIC devices, which allows the asymmetric LICs to be operated on either high energy mode (energy density of 114.7 Wh/kg at power density of 98.0 W/kg) or high power mode (power density of 60.1 kW/kg at energy density of 17.6 Wh/kg). The device also exhibited long-term cycle stability with 87% capacitance retention after 12 000 cycles. These results demonstrate that the rational design of nanoporous electrode structures can deliver a balanced, high-performance-activated cZIF-8 vertical bar Ni/NiO/C-based lithium-ion capacitor.
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.
Solution-Processable Quinoidal Dithioalkylterthiophene-Based Small Molecules Pseudo-Pentathienoacenes via an Intramolecular S center dot center dot center dot S Lock for High-Performance n-Type Organic Field-Effect Transistors
(2020-06-03)
Vegiraju, Sureshraju
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Torimtubun, Alfonsina Abat Amelenan
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Lin, Po-Shen
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Tsai, Hsin-Chia
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Lien, Wei-Chieh
A new organic small-molecule family comprising tetracyanoquinodimethane-substituted quinoidal dithioalky(SR)terthiophenes (DSTQs) (DSTQ-6 (1); SR = SC6H13, DSTQ : 10 (2); SR = SC10H21, DSTQ14 (3); SR = SC10H21) was synthesized and contrasted with a nonthioalkylated analogue (DRTQ14 (4); R = C14H29). The physical, electrochemical, and electrical properties of these new compounds are thoroughly investigated. Optimized geometries obtained from density functional theory calculations and single-crystal X-ray diffraction reveal the planarity of the SR-containing DSTQ core. DSTQs pack in a slipped pi-pi stacked two-dimensional arrangement, with a short intermolecular stacking distance of 3.55 A and short intermolecular S center dot center dot center dot N contacts of 3.56 angstrom. Thin-film morphological analysis by grazing incident X-ray diffraction reveals that all DSTQ molecules are packed in an edge-on fashion on the substrate. The favorable molecular packing, the high core planarity, and very low lowest unoccupied molecular orbital (LUMO) energy level (-4.2 eV) suggest that DSTQs could be electron-transporting semiconductors. Organic field-effect transistors based on solution-sheared DSTQ : 14 exhibit the highest electron mobility of 0.77 cm(2) V-1 s(-1) with good ambient stability, which is the highest value reported to date for such a solution process terthiophene-based small molecular semiconductor. These results demonstrate that the device performance of solution-sheared DSTQs can be improved by side chain engineering.
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.
Toward Long-Term Stable and Efficient Large-Area Organic Solar Cells
(2017-07-10)
Tsai, Pei-Ting
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Lin, Kuan-Chu
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Wu, Cheng-Yu
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Liao, Chung-Hung
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Lin, Man-Chun
Here, we report that long-term stable and efficient organic solar cells (OSCs) can be obtained through the following strategies: i) combination of rapid-drying blade-coating deposition with an appropriate thermal annealing treatment to obtain an optimized morphology of the active layer; ii) insertion of interfacial layers to optimize the interfacial properties. The resulting devices based on poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-2-carboxylate-2,6-diyl)] (PBDTTT-EFT):[6,6]-phenyl C-71 butyric acid methyl ester (PC71BM) blend as the active layer exhibits a power conversion efficiency (PCE) up to 9.57 %, which represents the highest efficiency ever reported for blade-coated OSCs. Importantly, the conventional structure devices based on poly(3-hexylthiophene) (P3HT):phenyl-C-61-butyric acid methyl ester (PCBM) blend can retain approximately 65% of their initial PCE for almost 2 years under operating conditions, which is the best result ever reported for long-term stable OSCs under operational conditions. More encouragingly, long-term stable large-area OSCs (active area = 216 cm(2)) based on P3HT:PCBM blend are also demonstrated. Our findings represent an important step toward the development of large-area OSCs with high performance and long-term stability.