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Investigating effect of strain on electronic and optical properties of lead free double perovskite Cs2AgInCl6 solar cell compound: A first principle calculation
摘要： Despite serious problems associated with toxicity of lead, lead halide perovskite based solar cells have resulted with remarkable efficiency and hence gained much interest. To overcome this aspect, numerous solutions are attempted by researchers which include the development of new environmental friendly lead free double perovskite (DP) photovoltaic materials. Enlightening on the same line, we report first principle calculations on electronic and optical properties of Cs2AgInCl6 solar photovoltaic materials. Present opto-electronic computations for lead free DP compound, have been performed using the full potential linearized augmented plane wave method. In present investigations, we have adopted exchange and correlation potentials prescribed by Perdew et al. and the most accurate Tran-Blaha modified Becke-Johnson. Both exchange and correlation potential computations are performed with and without spin orbit coupling. Results obtained for electronic and optical properties are validated by systematic comparison with available experimental data. Reasonable reconciliation between investigated results and the available experimental data, endorse accuracy of present computations. To identify the effect of strain on energy gap and hence on the optical properties of Cs2AgInCl6 compound, computations of electronic and optical properties have also been performed under the different values of strain application.
关键词： Density functional theory,Optical properties,Solar cells,Electronic structure
更新于2025-09-12 10:27:22
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Features of Vibrational and Electronic Structures of Decavanadate Revealed by Resonance Raman Spectroscopy and Density Functional Theory
摘要： Polyoxometalates are known to be inhibitors of a diverse collection of enzymes, although the specific interactions that lead to this bioactivity are still unclear. Spectroscopic characterization may be an invaluable if indirect tool for remedying this problem, yet this requires clear, cogent assignment of polyoxometalate spectra before the complicating effect of their binding to large biomolecules can be considered. We report the use of FT-IR and resonance Raman spectroscopies alongside density functional theory to describe the vibrational and electronic structures of decavanadate, [V10O28]6–. Our computational model, which reproduced the majority of vibrational features to within 10 cm–1, was then used to identify an axial oxo ligand as the most likely position of the acidic proton in the related cluster [HV10O28]5–. As resonance Raman spectroscopy can directly interrogate chromophores embedded in complex systems, this approach may be of general use in answering structural questions about polyoxometalate-enzyme systems.
关键词： vibrational and electronic structures,Polyoxometalates,decavanadate,density functional theory,resonance Raman spectroscopy
更新于2025-09-12 10:27:22
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Numerical Analysis of Quantum Plasmonic Metasuraface by Time-Dependent Density Functional Theory
摘要： We theoretically investigate optical properties of a quantum plasmonic metasurface composed of metallic nanoparticles that are arranged in a two-dimensional matrix form with a sub-nanometer gap. We employ a time-dependent density functional theory approach to calculate optical properties of the metasurface. They show characteristic features at gap distance smaller than 0.4 nm due to the tunneling currents that flow through the gaps.
关键词： optical properties,tunneling currents,time-dependent density functional theory,quantum plasmonic metasurface
更新于2025-09-12 10:27:22
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Side chain effect on conjugated polymer/fullerene interfaces in organic solar cells: a DFT study
摘要： Considerable experimental research has been conducted on the influence of polymer alkyl side chains on the performance of bulk heterojunction organic solar cells. However, greater insight into the role of alkyl side chains in the polymer/fullerene interfacial regions is still needed. Using the dispersion-corrected density functional theory, we investigate the effect of alkyl side chains on the binding energies and electronic structures of various molecular pairings of fullerenes and monomers of organic copolymers (e.g. a pair of PC71BM and a monomer of copolymer PTB7 based on the thieno[3,4-b]thiophene/benzodithiophene repeat unit, PCBM and a copolymer PCDTBT based on 2,7-carbazole/dithienyl-2,1,3-benzothiazole and PC71BM and a copolymer PffBT4T-2OD based on difluorobenzothiadiazole/quaterthiophene). We find that the trends of the magnitudes of the binding energies vary with the lengths, types (branched or linear), and branching positions of alkyl side chains. Whenever possible, these results are compared with the efficiency trends of the corresponding organic solar cells. With the help of this comparison optimal side chain arrangements in bulk heterogeneous organic solar cells are identified. It is expected that these insights will aid in the production of more efficient organic photovoltaics.
关键词： binding energies,polymer alkyl side chains,organic solar cells,dispersion-corrected density functional theory,bulk heterojunction,electronic structures
更新于2025-09-12 10:27:22
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New Optimal Control Problems in Density Functional Theory Motivated by Photovoltaics
摘要： We present and study novel optimal control problems motivated by the search for photovoltaic materials with high power-conversion e?ciency. The material must perform the ?rst step: convert light (photons) into electronic excitations. We formulate various desirable properties of the excitations as mathematical control goals at the Kohn–Sham-DFT level of theory, with the control being given by the nuclear charge distribution. We prove that nuclear distributions exist which give rise to optimal HOMO-LUMO excitations, and we present illustrative numerical simulations for one-dimensional ?nite nanocrystals. We observe pronounced goal-dependent features such as large electron-hole separation and a hierarchy of length scales: internal HOMO and LUMO wavelengths < atomic spacings < (irregular) ?uctuations of the doping pro?les < system size.
关键词： optimal control,excitations,photovoltaic materials,density functional theory,Kohn–Sham equations
更新于2025-09-12 10:27:22
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Evidence for vacancy trapping in Au-hyperdoped Si following pulsed laser melting
摘要： Nanosecond pulsed laser melting can be used to rapidly recrystallize ion-implanted Si through liquid phase epitaxy. The rapid resolidification that follows the melting results in a supersaturation of impurities and hyperdopes the Si, inducing novel optoelectronic properties with a wide range of applications. In this work, structural changes in the Si lattice in Au-hyperdoped Si are studied in detail. Specifically, we show that the local skewing of the lattice observed previously in regions of extremely high Au concentrations (>1.4 at. %) can be related to the displacement of Au from perfect lattice positions. Surprisingly, although the incorporation of the larger Au atoms into Si is expected to cause swelling of the lattice, reciprocal space mapping shows that a small amount (0.3 at. %) of lattice contraction (decrease in lattice parameter) is present in the hyperdoped layer. Furthermore, positron annihilation spectroscopy shows an elevated concentration of vacancies in the hyperdoped layer. Based on these observations and with the aid of density functional theory, we propose a phenomenological model in which vacancies are kinetically trapped into lattice sites around substitutional Au atoms during resolidification. This vacancy trapping process is hypothesized to occur as a means to minimize lattice strain and may be universal in pulsed laser melted Si systems.
关键词： vacancy trapping,lattice contraction,positron annihilation spectroscopy,density functional theory,pulsed laser melting,Au-hyperdoped Si
更新于2025-09-12 10:27:22
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Manganese doping mechanism in a CsPbI <sub/>2</sub> Br photovoltaic material: a first-principles study
摘要： As a light absorbing material of perovskite solar cells, Mn-doped CsPbI2Br has a better phase stability than the undoped one. In order to deeply understand the doping mechanism of Mn, the effect of substitutional and interstitial Mn doping on the structural, electronic and optical properties of CsPbI2Br has been investigated by first-principles calculations based on density functional theory. It is found that the binding energy of both the substitutional and the interstitial Mn-doped CsPbI2Br is negative and the binding energy difference between them is only 2.8 meV, which indicates that both the substitutional and the interstitial doping structures should be stable for Mn-doped CsPbI2Br and the latter is slightly preferred over the former due to the lower binding energy. The lattice parameters of CsPbI2Br change oppositely for two Mn-doping cases. Based on the comparative analysis of the electronic structures for CsPbI2Br and Mn-doped CsPbI2Br, we found that the substitutional doping of Mn introduces intermediate level, making CsPbI2Br an intermediate band semiconductor; for the interstitial bands near the Fermi Mn-doped CsPbI2Br the Fermi level enters conduction bands, making it an n-type semiconductor material with enhanced conductivity. The complex dielectric function and the absorption spectrum of Mn-doped and undoped CsPbI2Br were calculated and are basically consistent with the experimental results.
关键词： first-principles calculations,density functional theory,electronic and optical properties,perovskite solar cells,Mn-doped CsPbI2Br
更新于2025-09-12 10:27:22
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Infrared photodissociation spectroscopy of di-manganese oxide cluster cations
摘要： Infrared multiple-photon dissociation (IR-MPD) spectroscopy and density functional calculations have been employed to elucidate the geometric structure of a series of di-manganese oxide clusters Mn2Ox+ (x = 4–7). The theoretical exploration predicts that all investigated clusters contain a rhombus-like Mn2O2 core with up to four, terminally bound, oxygen atoms. The short Mn–O bond length of the terminal oxygen atoms of ～1.58 ? indicates triple bond character instead of oxyl radical formation. However, the IR-MPD spectra reveal that higher energy isomers with up to two O2 molecules η2-coordinated to the cluster core can be kinetically trapped under the given experimental conditions. In these complexes, all O2 units are activated to superoxide species. The sequential increase of the oxygen content in the cluster allows for a controlled increase of the positive charge localized on the Mn atoms reaching a maximum for Mn2O7+.
关键词： superoxide species,density functional theory,di-manganese oxide cluster cations,IR-MPD spectroscopy,Infrared photodissociation spectroscopy
更新于2025-09-12 10:27:22
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Photo-Switchable Boronic Acid Derived Salicylidenehydrazone Enabled by Photochromic Spirooxazine and Fulgide Moieties: Multiple Responses of Optical Absorption, Fluorescence Emission, and Quadratic Nonlinear Optics
摘要： A novel protocol of the boronic acid derived salicylidenehydrazone (BASHY) core being sandwiched by photochromic spirooxazine and fulgide moieties was proposed here to design multistate fluorescent photoswitches with variable nonlinear optical (NLO) responses. Systematic investigations on their optical absorption, fluorescence emission, and static first hyperpolarizabilities (β) were performed using density functional theory (DFT). It was found that the BASHY-based sandwiched series exhibited significant differences of absorption and emission properties between three photoisomers, which were essentially ascribed to the massive changes of corresponding electron transition characteristics quantified by hole–electron descriptors and visualized by electron density difference (EDD) plots. However, the isomerization of fulgide parts in the merocyanine (MC) form of spirooxazine failed to greatly shift maximum absorption/emission wavelengths, due to their high similarity of intrinsic transition features. Furthermore, large β contrasts between three photoisomers were observed, which resulted from significant variations of contributions of spirooxazine and/or fulgide moieties to the total β upon photoisomerization according to β densities. Although the fulgide moiety contributes negatively and positively to spirooxazine (SO) isomers when fulgide switches from close (C-) to open (E-) forms, respectively, their dominant βxxx values with opposite signs are still similar in magnitude, leading to quite close quadratic NLO responses. Therefore, the captivating ternary photoswitches with multiple responses of absorption, emission, and NLO were elaborately built in this context, promising to be applied as multifunctional optical materials in various scientific and technological fields.
关键词： photochromic spirooxazine,fulgide moieties,nonlinear optical (NLO) responses,density functional theory (DFT),boronic acid derived salicylidenehydrazone (BASHY)
更新于2025-09-12 10:27:22
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Vibrational Spectra of Thiolate-Protected Gold Nanocluster with Infrared Reflection Absorption Spectroscopy: Size- and Temperature-Dependent Ordering Behavior of Organic Monolayer
摘要： Vibrational spectra of thiolate-protected gold nanoclusters, prepared in a monolayer manner using the Langmuir?Blodgett method, were measured by means of infrared re?ection absorption spectroscopy (IRAS). A transferred monolayer of gold nanoclusters ligated by dodecanethiolate or 2-phenylethane-1-thiolate onto a single-crystal gold (Au) surface of Au(111) exhibits worthy IRAS spectra that reveal temperature-dependent behaviors from 100 to 340 K as well as comprehensive peak assignments based on density functional theory calculations: the conformation change in ligands between all trans and gauche defect forms with temperature. In addition to the temperature dependence, the cluster size dependence of alkyl and phenyl moieties is discussed, compared with the IRAS spectra of the corresponding self-assembled monolayers (SAMs) on Au(111). Ligands spreading three-dimensionally from the Au core determine the coordination structure of the ligated Au nanoclusters.
关键词： self-assembled monolayers,density functional theory calculations,Langmuir?Blodgett method,thiolate-protected gold nanoclusters,Vibrational spectra,temperature-dependent behaviors,infrared re?ection absorption spectroscopy
更新于2025-09-12 10:27:22