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Silver-chalcogen frameworks: crystal and electronic structure of [Ag3S](NO3) and a comparison with [Ag4Te](SO4)
摘要： Crystal and electronic structure of silver-containing metal-inorganic frameworks [Ag3S](NO3) and [Ag4Te](SO4) have been examined. For [Ag3S](NO3), the crystal structure has been re-determined from X-ray single crystal diffraction data and refined to R = 2.7% in order to determine the exact position of the nitrate anion. It is shown that the main structural feature of [Ag3S](NO3) and [Ag4Te](SO4) is the framework based on the combination of silver-chalcogen and silver-silver interactions, with guest oxoanions filling the cavities. Effectively, ionic interactions between guest anions and the framework differ significantly from the interactions within frameworks themselves, where the bonding analysis shows the tendency for more covalent bonding and indicates that the bonding patterns are consistent with what is regarded as metallophilic interactions.
关键词： Frameworks compounds,Silver,Solid-state structures,Metallophilic interactions,Electronic structure
更新于2025-09-19 17:15:36
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A rational design of excellent light-absorbing dyes with different N-substituents at the phenothiazine for high efficiency solar cells
摘要： Dye-sensitized solar cells (DSSCs) have attracted great interest due to their simple fabrication process and low cost. However, most organic dyes with D-π-A configuration usually exhibit narrow absorption band, leading to poor light harvesting ability and great loss on photon conversion efficiency. In this research, a series of excellent light-absorbing dyes (CC202-I – CC202-III) with different N-substituents at phenothiazine entities based on the champion dye CC202 were designed and investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT). According to the analysis of absorption property, the results demonstrated that different N-substituents (12-crown-4-substituted phenyl, 4-hexoxyphenyl, and bare phenyl) at phenothiazine entities lead to stronger and broader absorption band as well as red-shifted spectra; moreover, larger electronic injection driving force (ΔGinject), regeneration driving force (ΔGreg), capability of light harvested (LHE(λ)strong) and maximal photon generated current (Jph) in CC202-I – CC202-III are observed compared to that of CC202, which further increase JSC. Additionally, a larger VOC can be obtained in CC202-I – CC202-III due to larger dipole moment (μnormal) and slow electron recombination rate. Considering the all calculated characteristics related to JSC, dyes with 12-crown-4-substituted phenyl, 4-hexoxyphenyl, and bare phenyl substituent on phenothiazine can effectively enhance the photoelectric conversion efficiency of DSSCs.
关键词： Dye-sensitized solar cells,Electronic structure,Density functional theory,Light-absorbing
更新于2025-09-19 17:13:59
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Interface configuration effects on excitation, exciton dissociation, and charge recombination in organic photovoltaic heterojunction
摘要： The morphology of donor-acceptor heterojunction interface significantly affects the electron/hole processes in organic solar cells, including charge transfer (CT), exciton dissociation (ED), and charge recombination (CR). Here, to investigate interface molecular configuration effects, the donor-acceptor complexes with face-on, edge-on, and end-on configurations were constructed as model systems for the p-SIDT(FBTTh2)2/C60 heterojunction. The geometries, electronic structures, and excitation properties of monomers and the complexes with three configurations were studied based on density functional theory (DFT) and time-dependent DFT calculations with optimally tuned range separation parameters and solid polarization effects. In terms of Marcus theory, the rate constants of ED and CR processes were analyzed. The results show that most of the excited states for p-SIDT(FBTTh2)2 exhibit an intramolecular CT character, and the similarity of the excitation characters (CT and local excitation) and energies among three complexes with different configurations indicate that the electronic structure and excitation properties are insensitive to the interfacial molecular configurations. However, the rates of ED and CR processes heavily depend on it. These results underline the importance of controlling molecular configuration and then the morphology at the heterojunction interface in organic solar cells.
关键词： organic heterojunction interface,charge transfer,electronic structure,charge recombination
更新于2025-09-16 10:30:52
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Theoretical investigation of electronic bandgaps of semiconducting single-walled carbon nanotubes using semi-empirical self-consistent tight binding and <i>ab-inito</i> density functional methods
摘要： We perform a comprehensive theoretical study of electronic band gaps of semiconducting single-walled carbon nanotubes (SWNTs) with different sets of chiral indices using semi-empirical tight binding and density functional (DFT) based ab-initio methods. In particular, self-consistent extended Huckel (EH-SCF) and self-consistent Slater Koster (SK-SCF) tight binding models are used as semi-empirical methods, whereas the DFT based LDA-1/2 and Tran-Blaha (TB09) meta-GGA schemes are used as ab-initio methods. The calculations are performed for 1) (n, m) chiral SWNTs for which experimental optical gaps have been reported 2) (9, 0), (12, 0) and (15, 0) ‘metallic’ zigzag SWNTs for which small bad gaps have been reported 3) Pairs of SWNTs having same diameters but different chiral angles 4) (n, 0) zigzag SWNTs with ? ?n 30. From the comparison of bands gaps of tubes with same diameter, the electronic band gaps are found to vary with chiral angles with opposing trend as compared to that reported for experimental optical band gaps. This result may be expected to have important implications for self-energy corrections and/or exciton binding energies and their dependence on chiral angles. The hopping parameter g0 obtained from ?tting EH-SCF and SK-SCF bandgap data, is found to be in good agreement with that obtained from ?tting experimental data. In general, the band gap values of SWNTs computed using semi-empirical EH-SCF and SK-SCF methods are quite close (within ～ 5%) to those computed using DFT-based LDA-1/2 and TB09 meta-GGA methods. The results suggest that self-consistent semi-empirical methods can be expected to provide similar accuracy in results as that expected from more computationally challenging ab-intio DFT based LDA-1/2 and TB09 meta-GGA methods.
关键词： self-consistent tight binding method,semiconducting carbon nanotubes,electronic structure,first principles calculations
更新于2025-09-16 10:30:52
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Electronic Structure of Sr <sub/>1?</sub><i> <sub/>y</sub></i> Ca <i> <sub/>y</sub></i> Fe <sub/>2</sub> (As <sub/>1?</sub><i> <sub/>x</sub></i> P <i> <sub/>x</sub></i> ) <sub/>2</sub> ( <i>x</i> = 0.25, <i>y</i> = 0.08) Revealed by Angle-Resolved Photoemission Spectroscopy
摘要： We have investigated the electronic structure of Sr1?yCayFe2(As1?xPx)2 (x = 0.25, y = 0.08) by means of angle-resolved photoemission spectroscopy. From the comparison with the results of BaFe2(As1?xPx)2, the effects of smaller structural anisotropy (c/a) on the Fermi surfaces (FSs) and the gap structures are discussed. The observed FSs have three dimensional shapes. One of the hole FSs is strongly warped between the Γ and Z points, and the innermost FS observed at the Z point disappears at the Γ point, which is similar to the FS features of SrFe2(As1?xPx)2 (x = 0.35). In the superconducting state, the node like gap-minimum is present for the dxy electron FS near the X point, while the gaps around the other high symmetry points are isotropic. Several theoretical models based on the spin and/or the orbital fluctuation are examined to explain all these experimental results.
关键词： spin fluctuation,orbital fluctuation,electronic structure,Fermi surfaces,angle-resolved photoemission spectroscopy,superconducting gap
更新于2025-09-16 10:30:52
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LiZnN filled-tetrahedral compound: A first-principles study of the electronic, optical and effective mass properties
摘要： In the present contribution, first-principles calculation, based on the density functional theory using full-potential linearized augmented plane wave method, is applied to investigate the electronic structure and optical properties of LiZnN filled-tetrahedral compound. It is known that the density functional theory, using the generalized gradient approximation, underestimates the bandgap energy. Therefore, to overcome such difficulty, the regular and non-regular Tran-Blaha modified Becke-Johnson method has been used to obtain more accurate estimations of the compound properties and the bandgap energy. The non-regular Tran-Blaha modified Becke-Johnson method gives a significant improvement in the accuracy of the energy gap, in close agreement with the experimental results. Such a result is used to provide the Luttinger parameters, the dielectric constant and the effective masses. Moreover, an analysis of the electronic band structure and optical properties were carried out.
关键词： LiZnN,electronic structure,first-principles calculations
更新于2025-09-16 10:30:52
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Vacancy defect modulation in hot-casted NiO film for efficient inverted planar perovskite solar cell
摘要： Nickel oxide (NiOx) has exhibited great potential as an inorganic hole transport layer (HTL) in perovskite solar cells (PSCs) due to its wide optical bandgap and superior stability. In this study, we have modulated the Ni2+ vacancies in NiOx film by controlling deposition temperature in a hot-casting process, resulting the change of coordination structure and charge state of NiOx. Moreover, the change of the HOMO level of NiOx makes it more compatible with perovskite to decrease energy losses and enhance hole carrier injection efficiency. Besides, the defect modulation in the electronic structure of NiOx is beneficial for increasing the electrical conductivity and mobility, which are considered to achieve the balance of charge carrier transport and avoid charge accumulation at the interface between the perovskite and HTL effectively. Both experimental analyses and theoretical calculations reveal the increase of nickel vacancy defects change the electronic structure of NiOx by increasing the ratio of Ni3+/Ni2+ and improving the p-type characteristics. Accordingly, an optimal deposition temperature of the NiOx film at 120 °C enabled a 36.24% improvement in the power conversion efficiency compared to that deposited at room temperature (25 °C). Therefore, this work provides a facile method to manipulate the electronic structure of NiOx to improve the charge carrier transport and photovoltaic performance of related PSCs.
关键词： Electronic structure,Vacancy,Hole transport layer,Conductivity,Energy level,Mobility
更新于2025-09-16 10:30:52
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Calculation of electric field gradient in spherical quantum dots
摘要： We have calculated the ground and excited energy states of the quantum dot as a function of the depth of con?ning potential well and radius R. Based on the calculated energies and wave functions, the electric ?eld gradient induced by the non-spherical charge at the impurity is investigated as a function of dot radius and the con?ning potential. For Deuterium dot with spherical con?ning potential, the expectation value of the quadrupole moment operator is carried out. The calculations show that the con?ning potential and the impurity charge have a great in?uence on the electric ?eld gradient and the quadrupole moment. It is found that as the con?ning potential increases, the peak position of the electric ?eld gradient shifts toward smaller dot radii and its amplitude increases with the increase of con?ning potential.
关键词： quadrupole moment,electronic structure,Spherical quantum dot,electric ?eld gradient
更新于2025-09-16 10:30:52
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First-principles DFT insights into the structural, elastic, and optoelectronic properties of <i>α</i> and <i>β</i> -ZnP <sub/>2</sub> : implications for photovoltaic applications
摘要： Binary II–V semiconductors are highly optically active materials, possess high intrinsic mechanical and chemical durability, and have electronic properties ideal for optoelectronic applications. Among them, zinc diphosphide (ZnP2) is a promising earth-abundant absorber material for solar energy conversion. We have investigated the structural, mechanical, and optoelectronic properties of both the tetragonal (α) and monoclinic (β) phases of ZnP2 using standard, Hubbard-corrected and screened hybrid density functional theory methods. Through the analysis of bond character, band gap nature, and absorption spectra, we show that there exist two polymorphs of the β phase (denoted as β1 and β2) with distinct differences in the photovoltaic potential. While β1 exhibits the characteristics of metallic compounds, β2 is a semiconductor with predicted thin-film photovoltaic absorbing efficiency of almost 10%. The α phase is anticipated to be an indirect gap material with a calculated efficiency limited to only 1%. We have also analysed and gained insights into the electron localization function, projected density of states and projected crystal orbital Hamilton populations for the analogue bonds between the α and β-ZnP2. In light of these calculations, a number of previous discrepancies have been solved and a solid ground for future employment of zinc diphosphides in photovoltaics has been established.
关键词： photovoltaics,density functional theory,semiconductors,electronic structure
更新于2025-09-12 10:27:22
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Two-Dimensional Fluorine Distribution in a Heavily Distorted Perovskite Nickel Oxyfluoride Revealed by First-Principles Calculation
摘要： Most perovskite oxyfluorides synthesized to date have cubic structures, wherein fluorine atoms tend to reside at every oxygen site randomly. In this theoretical study, we show a two-dimensional fluorine arrangement in a perovskite nickel oxyfluoride (NdNiO2F) with a large orthorhombic distortion. The site selectivity in the perovskite lattice is due to the orthorhombicity, which stabilizes the two-dimensional cis configurations with shorter Ni?O and longer Ni?F bonds to minimize the electrostatic energy. The electronic structure of NdNiO2F is characterized by its large octahedral rotation and the higher electronegativity of fluorine than oxygen. We also observed how the anion arrangement was affected by the biaxial strain by modeling epitaxial strained thin film on substrate and found that the 2D cis structure remains the most stable. However, the orientation of the two-dimensional structure containing F depends on the magnitude of the biaxial strain. Our findings suggest that fluorine doping in orthorhombic perovskite oxides effectively yields oxyfluorides with anisotropic anion ordering.
关键词： electronic structure,orthorhombic distortion,perovskite oxyfluorides,two-dimensional fluorine arrangement,biaxial strain
更新于2025-09-12 10:27:22