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Influence of 2-Amino-4-methylpyridine and 2-Aminopyrimidine Ligands on the Malonic Acid-Cu(II) System: Insights through Supramolecular Interactions and Photoresponse Properties
摘要： Two Cu(II)-malonate complexes with 2-amino-4-methylpyridine (complex 1) and 2-aminopyrimidine (complex 2) auxiliary ligands were synthesized, and their single-crystal X-ray diffraction structures were established. Change in the auxiliary ligand exhibits substantial structural variation in the present complexes. Complex 1 shows a one-dimensional anionic copper-malonate moiety connected by the malonate bridge, whereas complex 2 is a mononuclear one. For both the complexes, auxiliary ligands are attached with the Cu-malonate moiety through various noncovalent interactions. Optical band gap, electrical conductivity, and photosensitivity of complexes 1 and 2 were measured, but the values of electrical parameters of the complexes significantly differ from each other. However, the magnitudes of electrical parameters increase several times for both the complexes when they are exposed under visible light, though the values of light sensing parameters of complex 1 were found to be higher than those of complex 2. Density functional theory calculations for complex 1 were carried out to support the experimental result.
关键词： 2-aminopyrimidine,electrical conductivity,Cu(II)-malonate complexes,density functional theory,2-amino-4-methylpyridine,optical band gap,noncovalent interactions,photosensitivity
更新于2025-09-16 10:30:52
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Simulation of quantum transport in doped carbon nanotube diode controlled by transverse electric field
摘要： Using first-principle and semi-empirical methods, optical responses and transport characteristics of hybrid CNT-based diodes are studied. The junction is realized by a combination of doping of one half of a nanotube and applying a transverse electric field to the other. Calculations are carried out in the framework of the density functional theory and the nonequilibrium Green function method. The possibility of using these rectifiers in optical nanoantennas is discussed.
关键词： density functional theory,nonequilibrium Green function method,transverse electric field,doped carbon nanotube diode,quantum transport,optical nanoantennas
更新于2025-09-16 10:30:52
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Self-Learning Method for Construction of Analytical Interatomic Potentials to Describe Laser-Excited Materials
摘要： Large-scale simulations using interatomic potentials provide deep insight into the processes occurring in solids subject to external perturbations. The atomistic description of laser-induced ultrafast nonthermal phenomena, however, constitutes a particularly difficult case and has so far not been possible on experimentally accessible length scales and timescales because of two main reasons: (i) ab initio simulations are restricted to a very small number of atoms and ultrashort times and (ii) simulations relying on electronic temperature- (Te) dependent interatomic potentials do not reach the necessary ab initio accuracy. Here we develop a self-learning method for constructing Te-dependent interatomic potentials which permit ultralarge-scale atomistic simulations of systems suddenly brought to extreme nonthermal states with density-functional theory (DFT) accuracy. The method always finds the global minimum in the parameter space. We derive a highly accurate analytical Te-dependent interatomic potential ΦeTeT for silicon that yields a remarkably good description of laser-excited and -unexcited Si bulk and Si films. Using ΦeTeT we simulate the laser excitation of Si nanoparticles and find strong damping of their breathing modes due to nonthermal melting.
关键词： nonthermal melting,laser-excited materials,silicon,interatomic potentials,density-functional theory
更新于2025-09-16 10:30:52
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Theoretical Study on Structural Properties of Silicon-doped Benzothiazole/SnO2 (100): A Novel Molecular Design for Solar Cells
摘要： Conjugated polymers have recently drawn interest owing to their high-power conversion efficiency in bulk heterojunction solar cells. Based on 4-(5-bromothiophen-2-yl)-7-(5-((4-nonyl-5-ethynylthiophen-2-yl) ethynyl)-thiophen-2-yl) benzothiadiazole (A4B7BT), organic polymer monomers for solar cells are designed, aided by silicon-doping, using density functional theory (DFT) at the GGA/PW91/DNP level. Comparison and screening of stable configuration, stable energy, and frontier orbital energy gap indicate that, A4B7BT-3Si is the best configuration when the positions of 1, 3, and 5 carbon atoms on the BT unit of A4B7BT are replaced by 3 Si atoms simultaneously. To further explore the photovoltaic (PV) properties of silicon-doped A4B7BT, DFT and the periodic plane slab model are combined to investigate A4B7BT-xSi (x=1–6) adsorbed on the SnO2 (100) surface. The stable structures, Mulliken charges, frontier orbitals, energy band structures, and density of states are discussed in detail. The results reveal that the energy gap (1.17 eV) in SnO2 (100)-A4B7BT-3Si is close to that of single-crystal Si. This study potentially guides the strategic development of future PV materials.
关键词： density functional theory,silicon-doped,4-(5-bromothiophen-2-yl)-7-(5-((4-nonyl-5-ethynylthiophen-2-yl)ethynyl)thiophen-2-yl)benzothiadiazole,SnO2 (100) surface
更新于2025-09-16 10:30:52
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Enhancing charge mobilities in self-assembled Na?ˉI halogen bonded organic semiconductors: A design approach based on experimental and computational perspectives
摘要： Charge transport in pyridine-ethynyliodophenyl supramolecules that involve intermolecular halogen bonding is studied by a combined experimental and computational approach. Selective fluorination of the molecules determines their crystallization pattern and is found to potentially increase the charge mobilities in the crystal. We report the synthesis of the molecules, full chemical characterization and resolved crystal structures. Computational analysis of the charge transport is provided to understand at the molecular level the structure-function relationships determining the charge mobilities. Combination of selective fluorination, halogen bonding motif and increased π system is highlighted as bearing the potential to achieve both enhanced hole and electron mobilities.
关键词： Selective fluorination and phenylation,Hole and electron mobility,Halogen bonding,Organic semiconductors,Charge transport,Density functional theory
更新于2025-09-16 10:30:52
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Density Functional Theory Investigation of Nonlinear Optical Properties of T-Graphene Quantum Dots
摘要： Using density functional theory calculations, we have analyzed nonlinear optical properties of a series of T-graphene quantum dots differing in their shape and size. Electronic polarizability, first-order and second-order hyperpolarizability of these systems are investigated and shed light on their stability and electronic properties. Negative cohesive energy shows that they are energetically stable. The effect of size and incident frequency on their nonlinear responses are comprehensively discussed. Most of the systems exhibit strong NLO response and it enhanced in the presence of external field. All these systems show absorption maximum ranging from UV to visible window. Overall, this theoretical framework highlighted the nonlinear optical properties of T-graphene quantum dots that may provide valuable information in designing potential NLO materials.
关键词： T-graphene quantum dot,electron delocalization,nonlinear optical property,UV-visible absorption spectra,Density functional theory
更新于2025-09-16 10:30:52
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Atomic-Level Microstructure of Efficient Formamidinium-Based Perovskite Solar Cells Stabilized by 5-Ammonium Valeric Acid Iodide Revealed by Multi-Nuclear and Two-Dimensional Solid-State NMR
摘要： Chemical doping of inorganic-organic hybrid perovskites is an effective way of improving the performance and operational stability of perovskite solar cells (PSCs). Here we use 5-ammonium valeric acid iodide (AVAI) to chemically stabilize the structure of α-FAPbI3. Using solid-state MAS NMR, we demonstrate the atomic-level interaction between the molecular modulator and the perovskite lattice and propose a structural model of the stabilized three-dimensional structure, further aided by density functional theory (DFT) calculations. We find that one-step deposition of the perovskite in the presence of AVAI produces highly crystalline films with large, micrometer-sized grains and enhanced charge-carrier lifetimes, as probed by transient absorption spectroscopy. As a result, we achieve greatly enhanced solar cell performance for the optimized AVA-based devices with a maximum power conversion efficiency (PCE) of 18.94%. The devices retain 90% of the initial efficiency after 300 h under continuous white light illumination and maximum-power point-tracking measurement.
关键词： power conversion efficiency,density functional theory,perovskite solar cells,chemical doping,solid-state MAS NMR,charge-carrier lifetimes,5-ammonium valeric acid iodide
更新于2025-09-16 10:30:52
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Tailoring of graphene quantum dots for toxic heavy metals detection
摘要： The sensitivity of graphene quantum dots towards toxic heavy metals (THMs; Cd, Hg, Pb) can be improved through doping with nitrogen at the vacant site defects. Using density functional theory, we investigate the adsorption of THMs on the graphene quantum dots (GQDs) and nitrogen-coordinated defective GQDs (GQD@1N, GQD@2N, GQD@3N and GQD@4N) surfaces. Thermochemistry calculations reveal that the adsorption of Pb atom on the surfaces is more favorable than Cd and Hg adsorption. The decoration of the vacant defects with nitrogen on the GQD surface substantially increases the charge transfer and adsorption energy values of THMs on the GQD surface (GQD@4N > GQD@3N > GQD@1N > GQD@2N > GQD). The charge transfer and adsorption energy of lead on each of these surfaces are greater than those of cadmium and mercury (Pb > Cd > Hg). Quantum theory of atoms in molecules analysis and non-covalent interaction plots further validate this result while also confirming that Pb atom has a partially covalent and electrostatic nature of interaction at the nitrogen-coordinated vacant site defects. The electron density values—a criterion of bond strength—for the THM...N interactions are greater than for the THM…C interactions, confirming the observed adsorption energy trends of the THMs on the surfaces. The lowering of the HOMO–LUMO energy gap of the surfaces follows the order Pb > Cd > Hg and also results in increased electrical conductivity, which are consistent with the calculated adsorption energy trends. Significant changes in the energy gap and electric conductivity of the surfaces upon THMs adsorption make them promising sensors for metal detection. Finally, time-dependent density functional theory calculations showed that changes such as peak shifts, peak quenching and appearance of new peaks are seen in the UV–visible absorption spectra of the surfaces upon adsorption of THMs, wherein the shifts in peaks correspond to the magnitude of adsorption energy of THMs on the surfaces. These results should motivate the experimentalists towards using rational and systematic modulation of surfaces as sensors for heavy metal detection.
关键词： Adsorption energy,Toxic heavy metals,Charge transfer,UV–visible absorption spectra,Nitrogen doping,Density functional theory,HOMO–LUMO energy gap,Graphene quantum dots
更新于2025-09-16 10:30:52
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Tuning the electronic, optical and structural properties of GaS/C2N van der Waals heterostructure for photovoltaic application: first-principle calculations
摘要： Due to the increased energy demand, a large amount of renewable energy is required to sustain the lives of people. The visible light semiconductors for photovoltaic cells with optical properties and a tunable bandgap have been studied to bring the solution to energy crises. Two-dimensional (2D) semiconductors including gallium sulphide (GaS) and carbon nitride (C2N) monolayers as a photovoltaic material were investigated by designing GaS/C2N van der Waals (vdWs) heterostructure. In this study, density functional theory (DFT) was employed to study the structural, photovoltaic applications, electronic and optical properties of GaS/C2N vdWs heterostructure. In comparison with the counterparts of GaS and C2N monolayers, the GaS/C2N vdWs heterostructure showed a lower desirable direct bandgap of 1.251 eV and the projected density of states shows a type-I band alignment. The work function of the heterostructure is much lesser than the GaS monolayer and C2N layer, which signifies that less energy will be needed for electrons to transfer from the ground state. The charge density transfer shows charge redistribution from GaS to C2N. The power conversion efficiency (η) of GaS/C2N heterostructure is calculated to be 17.8%. Based on the results, the 2D GaS/C2N heterostructure is predicted to be effective material in developing a high-performance photovoltaic device for future use.
关键词： Density functional theory,Heterostructure,Power conversion efficiency,Photovoltaic cells
更新于2025-09-16 10:30:52
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Comparing C60 and C70 as acceptor in organic solar cells: influence of the electronic structure and aggregation size on the photovoltaic characteristics
摘要： The difference in aggregation size of the C60 and C70 fullerenes affect the photovoltaic performance of devices assembled in the so-called bilayer architecture with poly[2,7-(9,9- dioctyl- dibenzosilole)- alt-4,7- bis(thiophen-2-yl)benzo- 2,1,3- thiadiazole] (PSiF-DBT) as the electron donor material. Despite the better performance of the C70 devices, which is related to the high absorption coefficient in the visible range and the superior charge transport properties, the short-circuit current variation upon annealing treatment at 100oC is approximately twice bigger when the C60 is the acceptor. We attribute this effect to the tendency of C60 in form smaller aggregate domains relatively to the C70. The increased roughness on the polymeric surface after annealing results in an enhanced donor/acceptor contact area and assists the fullerene diffusion deeper inside the polymeric layer. This effect leads to a better mixing between donor and acceptor species and create a interpenetrating layer close to the so-called bulk heterojunction. Since C60 forms smaller aggregates, this mechanism is more pronounced for this molecule. Therefore, a significant variation in the performance of the C60 devices is observed after this kind of treatment. Density Functional Theory calculations of the potential energy of interaction between two fullerene molecules and X-Ray measurements gives evidences to support this idea. In addition, combining spectrally resolved external quantum efficiency measurements with optical modeling our results also indicate the occurrence of the bilayer interfacial mixing for PSiF-DBT/C60.
关键词： Transfer matrix method,Density functional theory,Aggregation size,Fullerenes,Organic photovoltaics
更新于2025-09-16 10:30:52