Yao-Tsung Fu - Academia.edu (original) (raw)
Papers by Yao-Tsung Fu
Science China-Chemistry
We review some of the computational methodologies used in our research group to develop a better ... more We review some of the computational methodologies used in our research group to develop a better understanding of the geometric and electronic structures of organic-organic interfaces present in the active layer of organic solar cells. We focus in particular on the exciton-dissociation and charge-transfer processes at the pentacene-fullerene interface. We also discuss the local morphology at this interface on the basis of molecular dynamics simulations.
Fundamentals, Devices, and Upscaling, 2014
Science China-Chemistry, 2014
We review some of the computational methodologies used in our research group to develop a better ... more We review some of the computational methodologies used in our research group to develop a better understanding of the geometric and electronic structures of organic-organic interfaces present in the active layer of organic solar cells. We focus in particular on the exciton-dissociation and charge-transfer processes at the pentacene-fullerene interface. We also discuss the local morphology at this interface on the basis of molecular dynamics simulations. organic photovoltaics, organic-organic interface, multi-scale simulations
The Journal of Physical Chemistry C, 2011
ABSTRACT Bending and failure of aluminosilicate layers are common in polymer matrices although me... more ABSTRACT Bending and failure of aluminosilicate layers are common in polymer matrices although mechanical properties of curved layers and curvature limits are hardly known. We examined the mechanism of bending, the stored energy, and failure of several clay minerals. We employed molecular dynamics simulation, AFM data, and transmission electron microscopy (TEM) of montmorillonite embedded in epoxy and silk elastin polymer matrices with different weight percentage and different processing conditions. The bending energy per layer area as a function of bending radius can be converted into force constants for a given layer geometry and is similar for minerals of different cation exchange capacity (pyrophyllite, montmorillonite, mica). The bending energy increases from zero for a flat single layer to 10 mJ/m2 at a bending radius of 20 nm and exceeds 100 mJ/m2 at a bending radius of 6 nm. The smallest observed curvature of a bent layer is 3 nm. Failure proceeds through kink and split into two straight layers of shorter length. The mechanically stored energy per unit mass in highly bent aluminosilicate layers is close to the electrical energy stored in batteries. Molecular contributions to the bending energy include bond stretching and bending of bond angles in the mineral as well as rearrangements of alkali ions on the surface of the layers. When embedded in polymers, average radii of curvature of aluminosilicates exceed hundreds of nanometers. The small fraction of highly bent layers (<20 nm radius) can be increased by extrusion, especially in stacked layers, and by an increase in weight percentage of layered silicates above 5%. Extrusion also promotes failure and shortening of isolated layers.
Philosophical Magazine, 2010
The interlayer structure and cleavage energy of surfactant-modified clay minerals at the molecula... more The interlayer structure and cleavage energy of surfactant-modified clay minerals at the molecular level were determined for 50 different alkylammonium-modified montmorillonites of different cation exchange capacity (CECs of 91 meq/100 g and 143 meq/100 g), head group structure, and chain length using molecular dynamics simulation with specifically developed sampling techniques. The interlayer density and the cleavage energy are lower for partially packed, flat-on alkyl multilayers in the interlayer space and higher for densely packed, flat-on alkyl multilayers in the interlayer space, in agreement with trends in gallery spacing and molecular conformation. Particularly high cleavage energies, in excess of 60 mJ m, are found when charged head groups of surfactants are not vertically separated between the clay mineral layers at equilibrium distance due to strong contributions from Coulomb energy. A widely tunable range of cleavage energies between 25 and 210 mJ m was identified by simulation, whereas experimental data on the separation of modified layered clay minerals remain difficult to obtain. Alkylammonium-modified clay minerals with the lowest cleavage energy are of particular interest as additives for nanocomposites with increased potential for exfoliation without further chemical functionalization.
Journal of Applied Polymer Science, 2003
A series of nanocomposite hydrogels were prepared from various ratios of N-isopropylacrylamide (N... more A series of nanocomposite hydrogels were prepared from various ratios of N-isopropylacrylamide (NIPAAm) and organic montmorillonite (MMT). The influence of the extent of MMT in the NIPAAm/MMT nanocomposite hydrogels on the physical properties and drug-release behavior was the main purpose of this study. The microstructure and morphology were identified by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The results showed that the swelling ratios for these nanocomposite hydrogels decreased with increase in the content of MMT. The gel strength and Young's modulus of the gels also increased with increase in the content of MMT. XRD results indicated that the exfoliation of MMT was achieved in the swollen state. Finally, the drug-release behavior for the gels was also assessed.
Chemistry of Materials, 2010
Advanced Materials, 2013
ABSTRACT Molecular dynamics simulations of the pentacene-C(60) donor-acceptor interface reveal th... more ABSTRACT Molecular dynamics simulations of the pentacene-C(60) donor-acceptor interface reveal the potential for miscibility and disorder in "simple" bilayer organic photovoltaic architectures. The results fall in line with growing evidence of morphological complexity at such interfaces, and will impact descriptions of the electronic processes taking place during the photovoltaic effect.
Advanced Functional Materials, 2013
ABSTRACT The ability to detail how molecules pack in the bulk and at the various materials interf... more ABSTRACT The ability to detail how molecules pack in the bulk and at the various materials interfaces in the active layer of an organic solar cell is important to further understanding overall device performance. Here, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), a preferred electron-acceptor material in organic solar cells, is studied through molecular dynamics (MD) simulations; the goal is to examine the effects of temperature and trace solvents on the packing and morphological features of bulk PCBM. Solubility (miscibility) parameters, melting and order-disorder transitions, surface energies, and orientational distributions as a function of different starting configurations are discussed. On the basis of the derived morphologies, electronic structure calculations and a kinetic Monte Carlo approach are combined to evaluate the parameters impacting electron mobility in crystalline and amorphous PCBM structures.
Advanced Functional Materials, 2014
Science China-Chemistry
We review some of the computational methodologies used in our research group to develop a better ... more We review some of the computational methodologies used in our research group to develop a better understanding of the geometric and electronic structures of organic-organic interfaces present in the active layer of organic solar cells. We focus in particular on the exciton-dissociation and charge-transfer processes at the pentacene-fullerene interface. We also discuss the local morphology at this interface on the basis of molecular dynamics simulations.
Fundamentals, Devices, and Upscaling, 2014
Science China-Chemistry, 2014
We review some of the computational methodologies used in our research group to develop a better ... more We review some of the computational methodologies used in our research group to develop a better understanding of the geometric and electronic structures of organic-organic interfaces present in the active layer of organic solar cells. We focus in particular on the exciton-dissociation and charge-transfer processes at the pentacene-fullerene interface. We also discuss the local morphology at this interface on the basis of molecular dynamics simulations. organic photovoltaics, organic-organic interface, multi-scale simulations
The Journal of Physical Chemistry C, 2011
ABSTRACT Bending and failure of aluminosilicate layers are common in polymer matrices although me... more ABSTRACT Bending and failure of aluminosilicate layers are common in polymer matrices although mechanical properties of curved layers and curvature limits are hardly known. We examined the mechanism of bending, the stored energy, and failure of several clay minerals. We employed molecular dynamics simulation, AFM data, and transmission electron microscopy (TEM) of montmorillonite embedded in epoxy and silk elastin polymer matrices with different weight percentage and different processing conditions. The bending energy per layer area as a function of bending radius can be converted into force constants for a given layer geometry and is similar for minerals of different cation exchange capacity (pyrophyllite, montmorillonite, mica). The bending energy increases from zero for a flat single layer to 10 mJ/m2 at a bending radius of 20 nm and exceeds 100 mJ/m2 at a bending radius of 6 nm. The smallest observed curvature of a bent layer is 3 nm. Failure proceeds through kink and split into two straight layers of shorter length. The mechanically stored energy per unit mass in highly bent aluminosilicate layers is close to the electrical energy stored in batteries. Molecular contributions to the bending energy include bond stretching and bending of bond angles in the mineral as well as rearrangements of alkali ions on the surface of the layers. When embedded in polymers, average radii of curvature of aluminosilicates exceed hundreds of nanometers. The small fraction of highly bent layers (<20 nm radius) can be increased by extrusion, especially in stacked layers, and by an increase in weight percentage of layered silicates above 5%. Extrusion also promotes failure and shortening of isolated layers.
Philosophical Magazine, 2010
The interlayer structure and cleavage energy of surfactant-modified clay minerals at the molecula... more The interlayer structure and cleavage energy of surfactant-modified clay minerals at the molecular level were determined for 50 different alkylammonium-modified montmorillonites of different cation exchange capacity (CECs of 91 meq/100 g and 143 meq/100 g), head group structure, and chain length using molecular dynamics simulation with specifically developed sampling techniques. The interlayer density and the cleavage energy are lower for partially packed, flat-on alkyl multilayers in the interlayer space and higher for densely packed, flat-on alkyl multilayers in the interlayer space, in agreement with trends in gallery spacing and molecular conformation. Particularly high cleavage energies, in excess of 60 mJ m, are found when charged head groups of surfactants are not vertically separated between the clay mineral layers at equilibrium distance due to strong contributions from Coulomb energy. A widely tunable range of cleavage energies between 25 and 210 mJ m was identified by simulation, whereas experimental data on the separation of modified layered clay minerals remain difficult to obtain. Alkylammonium-modified clay minerals with the lowest cleavage energy are of particular interest as additives for nanocomposites with increased potential for exfoliation without further chemical functionalization.
Journal of Applied Polymer Science, 2003
A series of nanocomposite hydrogels were prepared from various ratios of N-isopropylacrylamide (N... more A series of nanocomposite hydrogels were prepared from various ratios of N-isopropylacrylamide (NIPAAm) and organic montmorillonite (MMT). The influence of the extent of MMT in the NIPAAm/MMT nanocomposite hydrogels on the physical properties and drug-release behavior was the main purpose of this study. The microstructure and morphology were identified by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The results showed that the swelling ratios for these nanocomposite hydrogels decreased with increase in the content of MMT. The gel strength and Young's modulus of the gels also increased with increase in the content of MMT. XRD results indicated that the exfoliation of MMT was achieved in the swollen state. Finally, the drug-release behavior for the gels was also assessed.
Chemistry of Materials, 2010
Advanced Materials, 2013
ABSTRACT Molecular dynamics simulations of the pentacene-C(60) donor-acceptor interface reveal th... more ABSTRACT Molecular dynamics simulations of the pentacene-C(60) donor-acceptor interface reveal the potential for miscibility and disorder in "simple" bilayer organic photovoltaic architectures. The results fall in line with growing evidence of morphological complexity at such interfaces, and will impact descriptions of the electronic processes taking place during the photovoltaic effect.
Advanced Functional Materials, 2013
ABSTRACT The ability to detail how molecules pack in the bulk and at the various materials interf... more ABSTRACT The ability to detail how molecules pack in the bulk and at the various materials interfaces in the active layer of an organic solar cell is important to further understanding overall device performance. Here, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), a preferred electron-acceptor material in organic solar cells, is studied through molecular dynamics (MD) simulations; the goal is to examine the effects of temperature and trace solvents on the packing and morphological features of bulk PCBM. Solubility (miscibility) parameters, melting and order-disorder transitions, surface energies, and orientational distributions as a function of different starting configurations are discussed. On the basis of the derived morphologies, electronic structure calculations and a kinetic Monte Carlo approach are combined to evaluate the parameters impacting electron mobility in crystalline and amorphous PCBM structures.
Advanced Functional Materials, 2014