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Electronic structure of hydroxylated La@C <sub/>82</sub> endohedral metallofullerene: implications on photovoltaic cells
摘要： The good performance of a photovoltaic device requires fitting a series of parameters related to electronic structure of materials. Since it is well-known that fullerenol is an excellent electron acceptor with excellent electron conductivity, in this paper we analyse the electronic levels, energy gaps, absorption spectra and electron mobility of hydroxylated La@C82 (La@C82(OH)n, n = 0?32) endohedral metallofullerene. Furthermore, calculations was performed on one unit of three donor polymers with low energy of the lowest unoccupied molecular orbital and on the well-known accep- tor fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) in order to compare the electronic structure and possible donor–acceptor combinations. Interestingly, high coatings have larger energy gap between the highest occupied molecular orbital of donor and the lowest unoccu- pied molecular orbital of acceptor, which is essential for increasing the open circuit voltage, which relates directly to power conversion efficiency. On the other hand, low coatings have better elec- tron mobility, which is essential in electron transport layers in perovskite-based solar cells. Finally, the absorption spectra of fullerenols were also calculated and compared with the widely used in organic solar cells PC61BM, obtaining a broader absorption spectrum in hydroxylated endohedral metallofullerenes helping in the performance of fullerenols for harvesting the solar spectrum.
关键词： density functional theory,absorption spectra,Solar cell,electronic structure tuning,endohedral metallofullerene
更新于2025-09-12 10:27:22
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How does the porphyrin-like vacancy affect the spectral properties of graphene quantum dots? A theoretical study
摘要： By processing graphene quantum dot, an ideal semiconductor material with suitable band gap and higher electron mobility can be obtained. Thus, it has a broad prospect in the application of photoelectric response materials. Here, a graphene defect with porphyrin-like structure is selected to achieve the controlable light absorption. The double five-membered-ring parallel vacancy are based on self-healing properties of popular graphene defects. Aimed to separate exciton and hole more effectively and achieve higher photoelectric conversion efficiency, the occupied orbital and unoccupied orbital of the quantum dot with objected defect structure is taken as orderly dispersion to form an obvious charge separation state under the demonstration with first principles calculation. Most importantly, a real time real space charge separation is calculated by time-dependent ab-initio quantum dynamics based on numerical atomic basis sets. The result shows the specific graphene defects can form an efficient pure graphene photoelectric response medium like porphyrin skeleton, and the vacancy will induce to adjust and control the specific wavelength of the response light and charge separated state manipulably with odevity of number of peripheral carbon rings by the calculation of ultrafast process.
关键词： Charge separation,Time-dependent density functional theory,Graphene defects
更新于2025-09-12 10:27:22
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Interaction of Graphene Quantum Dots with Oligothiophene: A Comprehensive Theoretical Study
摘要： Graphene/polythiophene composites are widely used in a variety of optoelectronic devices and applications, e.g., as electrode materials in capacitors and solar cells, but the detailed molecular-level relationship between their structural and electronic properties is not well understood. We present a density functional theory study of these composites using model systems consisting of graphene nanosheets and nanoribbons sandwiched between oligothiophenes (up to 13 monomers in length). These systems are investigated by computing optical band gaps, UV-vis spectra, densities of states, and by analyzing noncovalent interactions in terms of the reduced density gradient. Frontier molecular orbital analysis reveals a significant decrease in the optical band gap upon increasing the concentration of graphene, which can be tuned by adjusting the proportion of graphene using larger nanoribbons. This finding has implications for device design in these materials.
关键词： UV-vis Spectra,Composites,Optical Band Gap,Graphene,Noncovalent Interactions,Density Functional Theory,Polythiophene
更新于2025-09-12 10:27:22
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Intermediate band solar cell materials through the doping of group-VA elements (N, P, As and Sb) in Cu <sub/>2</sub> ZnSiSe <sub/>4</sub>
摘要： The electronic structure and optical properties of group-VA (N, P, As, and Sb)-doped Cu2ZnSiSe4 alloys have been studied using a hybrid functional through density functional theory calculations. The minor lattice distortion and small formation energy indicate that synthesis of these alloys is highly possible in experiment. For each doped alloy, an isolated and partially filled intermediate band (IB) appears in its band structure. The doping-induced IB is mainly contributed by the s states of the doped group-VA atom and the p states of four neighboring Se atoms, and slightly by the d states of eight Cu atoms. The existence of an IB obviously enhances the absorption coefficient with two additional absorption peaks in the visible light range. For P, As and Sb-doped Cu2ZnSiSe4 alloys, not only the bandgap between the valence band maximum and the conduction band minimum but also the sub bandgap between the valence band maximum and the IB are very close to the optimal values for visible light absorption. Therefore, these alloys are recommended as good candidates for IB solar cell materials.
关键词： intermediate band solar cell,optical properties,Cu2ZnSiSe4,group-VA elements,density functional theory
更新于2025-09-11 14:15:04
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Optical Properties of Buckled Bismuthene
摘要： In this paper, the optical properties of buckled bismuthene (a new 2D material) are studied in different strains. Different transitions in bismuthene’s band structure are mentioned and the optical advantages of buckled bismuthene are discussed. It is found that buckled bismuthene is strain independent infrared (IR) reducer and could be used in bio photonics.
关键词： 2D material,optical properties,reflection,group V monolayers,honeycomb lattice,absorption spectra,density functional theory,dielectric function,buckled bismuthene
更新于2025-09-11 14:15:04
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Designing strained C2N/GaTe(InTe) heterostructures for photovoltaic and photocatalytic application
摘要： Converting solar energy into electrical energy or chemical energy is a promising strategy to produce renewable clean energy. Here, we investigate the electronic structures of the C2N/MTe (M ? Ga, In) heterostructures under strain based on the density functional theory. The C2N/MTe van der Waals heterostructures possess great room temperature stability and exhibit excellently optoelectronic properties that desired for photocatalysis and photovoltaic conversion. Furthermore, strain engineering is utilized to tune the electronic structure. The results show that the exciton Bohr radius is almost insensitive to the strain in C2N/GaTe heterostructure, while the compressive strain can decrease the exciton Bohr radius in C2N/InTe heterostructure. Moreover, the power conversion ef?ciency can reach 22.1% for C2N/GaTe heterostructure with 4% strain and 19.8% for C2N/InTe heterostructure with 6% strain. Our results show that the tensile strain is a great strategy to improve the optoelectronic performance of C2N/MTe heterostructures.
关键词： Density functional theory,Strain effect,Photovoltaics,Heterostructure,Photocatalysis
更新于2025-09-11 14:15:04
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Color tunable carbon quantum dots from wasted paper by different solvents for anti-counterfeiting and fluorescent flexible film
摘要： Forecasting the structural stability of hybrid organic/inorganic compounds, where polyatomic molecules replace atoms, is a challenging task; the composition space is vast, and the reference structure for the organic molecules is ambiguously defined. In this work, we use a range of machine-learning algorithms, constructed from state-of-the-art density functional theory data, to conduct a systematic analysis on the likelihood of a given cation to be housed in the perovskite structure. In particular, we consider both ABC3 chalcogenide (I?V?VI3) and halide (I?II?VII3) perovskites. We find that the effective atomic radius and the number of lone pairs residing on the A-site cation are sufficient features to describe the perovskite phase stability. Thus, the presented machine-learning approach provides an efficient way to map the phase stability of the vast class of compounds, including situations where a cation mixture replaces a single A-site cation. This work demonstrates that advanced electronic structure theory combined with machine-learning analysis can provide an efficient strategy superior to the conventional trial-and-error approach in materials design.
关键词： hybrid organic/inorganic compounds,perovskite,density functional theory,machine-learning,phase stability
更新于2025-09-11 14:15:04
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Enhanced piezoresponse and nonlinear optical properties of fluorinated self-assembled peptide nanotubes
摘要： Self-assembled L,L-diphenylalanine (FF) nanostructures offer an attractive platform for photonics and nonlinear optics. The nonlinear optical (NLO) coefficients of FF nanotubes depend on the diameter of the tube [S. Khanra et al. Phys. Chem. Chem. Phys. 19(4), 3084–3093 (2017)]. To further enhance the NLO properties of FF, we search for structural modifications. Here, we report on the synthesis of fluorinated FF dipeptides by replacing one ortho-hydrogen atom in each of the phenyl groups of FF by a fluorine atom. Density-functional theoretical calculations yield insights into minimum energy conformers of fluorinated FF (Fl-FF). Fl-FF self-assembles akin to FF into micron-length tubes. The effects of fluorination are evaluated on the piezoelectric response and nonlinear optical properties. The piezoelectric d15 coefficient of Fl-FF is found to be more than 10 times higher than that of FF nanotubes, and the intensity of second harmonic generation (SHG) polarimetry from individual Fl-FF nanotubes is more than 20 times that of individual FF nanotubes. Furthermore, we obtain SHG images to compare the intensities of FF and Fl-FF tubes. This work demonstrates the potential of fluorine substitution in other self-assembled biomimetic peptides for enhancing nonlinear optical response and piezoelectricity.
关键词： piezoresponse,density-functional theory,nonlinear optical properties,fluorinated self-assembled peptide nanotubes,second harmonic generation
更新于2025-09-11 14:15:04
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Identification and Characterization of ‘Killer-Modes’ in Organic Semiconductors with Terahertz Spectroscopy
摘要： Organic semiconductors are promising modern optoelectric materials, with countless potential applications ranging from ?exible displays to photovoltaics. The applicability of these materials is largely driven by their charge carrier mobility, which is strongly in?uenced by low-frequency vibrations. In this work, the speci?c low-frequency vibrations that exhibit strong electron-phonon coupling, deemed ‘killer-modes’, in organic semiconductors are determined using a combination of terahertz time-domain spectroscopy and solid-state density functional theory. The results of this study enable a concerted synthetic effort to rationally design novel materials, utilizing intermolecular forces to stiffen lattice dynamics, to ultimately improve charge carrier mobility.
关键词： electron-phonon coupling,organic semiconductors,charge carrier mobility,solid-state density functional theory,terahertz spectroscopy
更新于2025-09-11 14:15:04
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Theoretical Study of Ternary CoSP Semiconductor: A Candidate for Photovoltaic Applications
摘要： The electronic structure of pyrite-type cobalt phosphosulfide (CoSP) is studied using density-functional theory. The calculated band structure reveals the non-magnetic semiconducting character of the compound. The electronic structure is described using the electronic band structure and the densities of states. A band gap of 1.14 eV is computed within standard GGA, a value which is enhanced using hybrid functional. It separates the upper part of the valence band dominated by Co-3d-t2g states from the lower part of the conduction band made exclusively of Co-3d-eg, above of which lie S-3p and P-3p ones. The obtained values are suitable for applications in solar cells, according to Shockley–Queisser theory of light-to-electric conversion efficiency. The origin of the larger CoSP band gap, with respect to the one of the promising FeS2 compound, is explained and the chemical bonding properties are addressed. A comparative picture is established where several similarities are found, suggesting that CoSP could be of great practical interest in photovoltaics.
关键词： band gaps,pyrite disulfides,photovoltaics,chemical bondings,density-functional theory
更新于2025-09-11 14:15:04