scholarly journals Unraveling the Effect of Defects, Domain Size, and Chemical Doping on Photophysics and Charge Transport in Covalent Organic Frameworks

2021 ◽  
Author(s):  
Raja Ghosh ◽  
Francesco Paesani
Keyword(s):  
Charge Transport ◽  
Three Dimensional ◽  
Domain Size ◽  
Quantitative Agreement ◽  
Conclusive Evidence ◽  
Chemical Doping ◽  
Covalent Organic Frameworks ◽  
Systematic Analysis ◽  
Major Interest ◽  
Coherence Lengths

We present a novel theoretical approach to understanding the effect of electronic defects, domain size, and chemical dopants on the infrared spectral line shape and three-dimensional charge transport of positively charged polarons (“holes”) in doped (and undoped) Covalent Organic Frameworks (COFs). The simulated spectra are in excellent agreement with very recent measurements conducted on Iodine doped COF films. Through a detailed systematic analysis, we can also determine the polaron coherence lengths both along the 2D COF plane (intraframework) and through the molecular columns (interframework). The coherence lengths are important quantities in determining the anisotropic charge mobilities and conductivities in such films and are therefore of major interest in understanding the operation of organic electronic devices such as transistors and solar cells. By obtaining the first quantitative agreement with iodine doped TANG-COF, we identify well defined spectral signatures that provides conclusive evidence on why doped COFS have so far shown lower bulk conductivity compared to doped polythiophenes.

scholarly journals Unraveling the Effect of Defects, Domain Size, and Chemical Doping on Photophysics and Charge Transport in Covalent Organic Frameworks

2021 ◽  
Author(s):  
Raja Ghosh ◽  
Francesco Paesani
Keyword(s):  
Charge Transport ◽  
Three Dimensional ◽  
Domain Size ◽  
Quantitative Agreement ◽  
Conclusive Evidence ◽  
Chemical Doping ◽  
Covalent Organic Frameworks ◽  
Systematic Analysis ◽  
Major Interest ◽  
Coherence Lengths

We present a novel theoretical approach to understanding the effect of electronic defects, domain size, and chemical dopants on the infrared spectral line shape and three-dimensional charge transport of positively charged polarons (“holes”) in doped (and undoped) Covalent Organic Frameworks (COFs). The simulated spectra are in excellent agreement with very recent measurements conducted on Iodine doped COF films. Through a detailed systematic analysis, we can also determine the polaron coherence lengths both along the 2D COF plane (intraframework) and through the molecular columns (interframework). The coherence lengths are important quantities in determining the anisotropic charge mobilities and conductivities in such films and are therefore of major interest in understanding the operation of organic electronic devices such as transistors and solar cells. By obtaining the first quantitative agreement with iodine doped TANG-COF, we identify well defined spectral signatures that provides conclusive evidence on why doped COFS have so far shown lower bulk conductivity compared to doped polythiophenes.

scholarly journals Unraveling the Effect of Defects, Domain Size, and Chemical Doping on Photophysics and Charge Transport in Covalent Organic Frameworks

2021 ◽  
Author(s):  
Raja Ghosh ◽  
Francesco Paesani
Keyword(s):  
Charge Transport ◽  
Domain Size ◽  
Chemical Doping ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
Physical Mechanisms

Understanding the underlying physical mechanisms that govern charge transport in two-dimensional (2D) covalent organic frameworks (COFs) will facilitate the development of novel COF-based devices for optoelectronic and thermoelectric applications. In this...

scholarly journals The Influence of Morphology on the Charge Transport in Two-Phase Disordered Organic Systems

2015 ◽  
Vol 1737 ◽  
Author(s):  
Cristiano F. Woellner ◽  
Leonardo D. Machado ◽  
Pedro A. S. Autreto ◽  
José A. Freire ◽  
Douglas S. Galvão
Keyword(s):  
Charge Transport ◽  
Master Equation ◽  
Carrier Mobility ◽  
Three Dimensional ◽  
Domain Size ◽  
Threshold Field ◽  
Phase System ◽  
Two Phase ◽  
Donor Acceptor ◽  
Pauli Master Equation

ABSTRACTIn this work we use a three-dimensional Pauli master equation to investigate the charge carrier mobility of a two-phase system, which can mimic donor-acceptor and amorphous-crystalline bulk heterojunctions. Our approach can be separated into two parts: the morphology generation and the charge transport modeling in the generated blend. The morphology part is based on a Monte Carlo simulation of binary mixtures (donor/acceptor). The second part is carried out by numerically solving the steady-state Pauli master equation. By taking the energetic disorder of each phase, their energy offset and domain morphology into consideration, we show that the carrier mobility can have a significant different behavior when compared to a one-phase system. When the energy offset is non-zero, we show that the mobility electric field dependence switches from negative to positive at a threshold field proportional to the energy offset. Additionally, the influence of morphology, through the domain size and the interfacial roughness parameters, on the transport was also investigated.

Design and Synthesis of Two-Dimensional Covalent Organic Frameworks with Four-Arm Cores: Prediction of Remarkable Ambipolar Charge-Transport Properties

2019 ◽  
Author(s):  
Simil Thomas ◽  
Hong Li ◽  
Raghunath R. Dasari ◽  
Austin Evans ◽  
William Dichtel ◽  
...  
Keyword(s):  
Charge Transport ◽  
Organic Semiconductors ◽  
Density Functional ◽  
Polymer Networks ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
X Ray Diffraction ◽  
Zinc Porphyrin ◽  
Design And Synthesis ◽  
Predicted Values

<p>We have considered three two-dimensional (2D) π-conjugated polymer networks (i.e., covalent organic frameworks, COFs) materials based on pyrene, porphyrin, and zinc-porphyrin cores connected <i>via</i> diacetylenic linkers. Their electronic structures, investigated at the density functional theory global-hybrid level, are indicative of valence and conduction bands that have large widths, ranging between 1 and 2 eV. Using a molecular approach to derive the electronic couplings between adjacent core units and the electron-vibration couplings, the three π-conjugated 2D COFs are predicted to have ambipolar charge-transport characteristics with electron and hole mobilities in the range of 65-95 cm<sup>2</sup>V<sup>-1</sup>s<sup>-1</sup>. Such predicted values rank these 2D COFs among the highest-mobility organic semiconductors. In addition, we have synthesized the zinc-porphyrin based 2D COF and carried out structural characterization via powder X-ray diffraction and surface area analysis, which demonstrates the feasability of these electroactive networks.</p>

scholarly journals Lath Martensite Microstructure Modeling: A High-Resolution Crystal Plasticity Simulation Study

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 691
Author(s):  
Francisco-José Gallardo-Basile ◽  
Yannick Naunheim ◽  
Franz Roters ◽  
Martin Diehl
Keyword(s):  
High Resolution ◽  
Mechanical Behavior ◽  
Crystal Plasticity ◽  
Lath Martensite ◽  
Three Dimensional ◽  
Building Blocks ◽  
Quantitative Agreement ◽  
Carbon Steels ◽  
Plastic Behavior ◽  
Austenitic Phase

Lath martensite is a complex hierarchical compound structure that forms during rapid cooling of carbon steels from the austenitic phase. At the smallest, i.e., ‘single crystal’ scale, individual, elongated domains, form the elemental microstructural building blocks: the name-giving laths. Several laths of nearly identical crystallographic orientation are grouped together to blocks, in which–depending on the exact material characteristics–clearly distinguishable subblocks might be observed. Several blocks with the same habit plane together form a packet of which typically three to four together finally make up the former parent austenitic grain. Here, a fully parametrized approach is presented which converts an austenitic polycrystal representation into martensitic microstructures incorporating all these details. Two-dimensional (2D) and three-dimensional (3D) Representative Volume Elements (RVEs) are generated based on prior austenite microstructure reconstructed from a 2D experimental martensitic microstructure. The RVEs are used for high-resolution crystal plasticity simulations with a fast spectral method-based solver and a phenomenological constitutive description. The comparison of the results obtained from the 2D experimental microstructure and the 2D RVEs reveals a high quantitative agreement. The stress and strain distributions and their characteristics change significantly if 3D microstructures are used. Further simulations are conducted to systematically investigate the influence of microstructural parameters, such as lath aspect ratio, lath volume, subblock thickness, orientation scatter, and prior austenitic grain shape on the global and local mechanical behavior. These microstructural features happen to change the local mechanical behavior, whereas the average stress–strain response is not significantly altered. Correlations between the microstructure and the plastic behavior are established.

scholarly journals Evaluating variability in coseismic slips of paleoearthquakes from an incomplete slip history: an example from displaced terrace flights across the Kamishiro fault, central Japan

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Naoya Takahashi ◽  
Shinji Toda
Keyword(s):  
Monte Carlo ◽  
Three Dimensional ◽  
Seismic Hazard Assessment ◽  
Probabilistic Seismic Hazard Assessment ◽  
Reverse Fault ◽  
Central Japan ◽  
Systematic Analysis ◽  
Fluvial Terraces ◽  
Rupture Length ◽  
Slip History

AbstractExamining the regularity in slip over seismic cycles leads to an understanding of earthquake recurrence and provides the basis for probabilistic seismic hazard assessment. Systematic analysis of three-dimensional paleoseismic trenches and analysis of offset markers along faults reveal slip history. Flights of displaced terraces have also been used to study slips of paleoearthquakes when the number of earthquakes contributing to the observed displacement of a terrace is known. This study presents a Monte Carlo-based approach to estimating slip variability using displaced terraces when a detailed paleoseismic record is not available. First, we mapped fluvial terraces across the Kamishiro fault, which is an intra-plate reverse fault in central Japan, and systematically measured the cumulative dip slip of the mapped terraces. By combining these measurements with the age of the paleoearthquakes, we estimated the amount of dip slip for the penultimate event (PE) and antepenultimate event (APE) to be 1.6 and 3.4 m, respectively. The APE slip was nearly three times larger than the most recent event of 2014 (Mw 6.2): 1.2 m. This suggests that the rupture length of the APE was much longer than that of the 2014 event and the entire Kamishiro fault ruptured with adjacent faults during the APE. Thereafter, we performed the Monte Carlo simulations to explore the possible range of the coefficient of variation for slip per event (COVs). The simulation considered all the possible rupture histories in terms of the number of events and their slip amounts. The resulting COVs typically ranged between 0.3 and 0.54, indicating a large variation in the slip per event of the Kamishiro fault during the last few thousand years. To test the accuracy of our approach, we performed the same simulation to a fault whose slip per event was well constrained. The result showed that the error in the COVs estimate was less than 0.15 in 86% of realizations, which was comparable to the uncertainty in COVs derived from a paleoseismic trenching. Based on the accuracy test, we conclude that the Monte Carlo-based approach should help assess the regularity of earthquakes using an incomplete paleoseismic record.

scholarly journals Molecular Characterization of Pax62Neu Through Pax610Neu: An Extension of the Pax6 Allelic Series and the Identification of Two Possible Hypomorph Alleles in the Mouse Mus musculus

Genetics ◽  
2001 ◽  
Vol 159 (4) ◽  
pp. 1689-1700
Author(s):  
Jack Favor ◽  
Heiko Peters ◽  
Thomas Hermann ◽  
Wolfgang Schmahl ◽  
Bimal Chatterjee ◽  
...  
Keyword(s):  
Amino Acid ◽  
Molecular Characterization ◽  
Amino Acid Substitution ◽  
Gene Dosage ◽  
Three Dimensional ◽  
Null Alleles ◽  
Target Sequence ◽  
Allelic Series ◽  
Phenotypic Analysis ◽  
Major Interest

Abstract Phenotype-based mutagenesis experiments will increase the mouse mutant resource, generating mutations at previously unmarked loci as well as extending the allelic series at known loci. Mapping, molecular characterization, and phenotypic analysis of nine independent Pax6 mutations of the mouse recovered in mutagenesis experiments is presented. Seven mutations result in premature termination of translation and all express phenotypes characteristic of null alleles, suggesting that Pax6 function requires all domains to be intact. Of major interest is the identification of two possible hypomorph mutations: Heterozygotes express less severe phenotypes and homozygotes develop rudimentary eyes and nasal processes and survive up to 36 hr after birth. Pax64Neu results in an amino acid substitution within the third helix of the homeodomain. Three-dimensional modeling indicates that the amino acid substitution interrupts the homeodomain recognition α-helix, which is critical for DNA binding. Whereas cooperative dimer binding of the mutant homeodomain to a paired-class DNA target sequence was eliminated, weak monomer binding was observed. Thus, a residual function of the mutated homeodomain may explain the hypomorphic nature of the Pax64Neu allele. Pax67Neu is a base pair substitution in the Kozak sequence and results in a reduced level of Pax6 translation product. The Pax64Neu and Pax67Neu alleles may be very useful for gene-dosage studies.

Multi-Objective Optimization of a Microturbine Compact Recuperator

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Diego Micheli ◽  
Valentino Pediroda ◽  
Stefano Pieri
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Design Procedure ◽  
Domain Size ◽  
Multidisciplinary Optimization ◽  
Computational Domain ◽  
Surface Geometry ◽  
Multi Objective ◽  
Flux Boundary Conditions

An automatic approach for the multi-objective shape optimization of microgas turbine heat exchangers is presented. According to the concept of multidisciplinary optimization, the methodology integrates a CAD parametric model of the heat transfer surfaces, a three-dimensional meshing tool, and a CFD solver, all managed by a design optimization platform. The repetitive pattern of the surface geometry has been exploited to reduce the computational domain size, and the constant flux boundary conditions have been imposed to better suit the real operative conditions. A new approach that couples cold and warm fluids in a periodic unitary cell is introduced. The effectiveness of the numerical procedure was verified comparing the numerical results with available literature data. The optimization objectives are maximizing the heat transfer rate and minimizing both friction factor and heat transfer surface. The paper presents the results of the optimization of a 50kWMGT recuperator. The design procedure can be effectively extended and applied to any industrial heat exchanger application.

Thermocapillary Convection With Undeformable Curved Surfaces in Open Cylinders

2001 ◽  
Author(s):  
Bok-Cheol Sim ◽  
Abdelfattah Zebib
Keyword(s):  
Free Surface ◽  
Critical Frequency ◽  
Thermocapillary Convection ◽  
Three Dimensional ◽  
Quantitative Agreement ◽  
Fluid Volume ◽  
Uniform Heat Flux ◽  
Free Surfaces ◽  
Space Experiments ◽  
Steady Convection

Abstract Thermocapillary convection driven by a uniform heat flux in an open cylindrical container of unit aspect ratio is investigated by two- and three-dimensional numerical simulations. The undeformable free surface is either flat or curved as determined by the fluid volume (V ≤ 1) and the Young-Laplace equation. Convection is steady and axisymmetric at sufficiently low values of the Reynolds number (Re) with either flat or curved interfaces. Only steady convection is possible in strictly axisymmetric computations. Transition to oscillatory three-dimensional motions occurs as Re increases beyond a critical value dependent on Pr and V. With a flat free surface (V = 1), two-lobed pulsating waves are found on the free surface and prevail with increasing Re. While the critical Re increases with increasing Pr, the critical frequency decreases. In the case of a concave surface, four azimuthal waves are found rotating clockwise on the surface. The critical Re decreases with increasing fluid volume, and the critical frequency is found to increase. The numerical results with either flat or curved free surfaces are in good quantitative agreement with space experiments.

Three-Dimensional Covalent Organic Frameworks with hea Topology

2021 ◽  
Author(s):  
Zonglong Li ◽  
Li Sheng ◽  
Chouhung Hsueh ◽  
Xiaolin Wang ◽  
Hao Cui ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Covalent Organic Frameworks
Sign in / Sign up

Export Citation Format

Share Document