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N719 Derivatives for Application in a Dye-Sensitized Solar Cell (DSSC): A Theoretical Study
摘要： The primary goal of this investigation is to analyze the influence of the chemical modifications on the electronic structures of N719 derivatives for their use in Dye-Sensitized Solar Cells (DSSC), by employing Density Functional Theory (DFT). UV-Visible spectra indicate that the electronic configurations are essential to study the absorption of solar irradiation and to analyze the charge transport mechanism between the Electron Transport Layer (ETL), the electrolyte, and the dye. Open and closed-shell electronic configurations are related to the absorption and the excitation energies of the dye. According to the results reported here, it is possible to say that the best candidates are N719, N719-2, N719-7, and N719-8 (neutral and di-anionic). They may be used as useful dye sensitizers due to their bandgap and band alignment with the ETL, which contributes to having an effective charge transport during the functioning of the solar device. Another parameter that is reported in this investigation is the Light-Harvesting Efficiency (LHE) for all studied systems. This could help to improve the performance of the device since there is an increment in the generation of charge carriers. These results could be useful as a guide for experimental investigations on chemical modifications of these sensitizers.
关键词： UV-Visible Spectra,Light-Harvesting Efficiency,Molecular Structure,Spectroscopy,DFT,N719 Derivatives,Theoretical Study,Quantum Chemistry,Density Functional Theory,DSSC,Dye-Sensitized Solar Cell,LHE
更新于2025-09-12 10:27:22
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Revealing Long-Range Substituent Effects in the Laser-Induced Fluorescence and Dispersed Fluorescence Spectra of Jet-Cooled CH <sub/><i>x</i> </sub> F <sub/> 3– <i>x</i> </sub> CH <sub/>2</sub> O ( <i>x</i> = 1, 2, 3) Radicals
摘要： The B?←X? laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of the atmospherically important β-monofluoro ethoxy (MFEO), β,β-difluoro ethoxy (DFEO), and β,β,β-trifluoro ethoxy (TFEO) radicals were recorded with vibronic resolution under jet-cooled conditions. To simulate the spectra, Franck-Condon factors were obtained from quantum chemical computations carried out at the CAM-B3LYP/6-311++G(d,p) level of theory. The simulations reproduce well both the LIF and DF spectra. Both conformers (G and T) of MFEO and one (G) of the two conformers of DFEO contribute to the LIF spectrum. A comparison between the experimental and calculated spectra confirms the expected long-range field effects of the CHxF3?x group on electronic transition energies and bond strengths, especially in the excited electronic (B?) state. Although TFEO has only one conformer, its LIF spectrum is highly congested, which is attributed to the interaction between CO stretch and the ?CF3 internal rotation.
关键词： Laser-Induced Fluorescence,Molecular Structure,Spectroscopy,Quantum Chemistry,Fluoroethoxy Radicals,Jet-cooled,Dispersed Fluorescence
更新于2025-09-12 10:27:22
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Ultrafast vibrational coupling between C H and C O band of cyclic amide 2-Pyrrolidinone revealed by 2DIR spectroscopy
摘要： Coupling between C–H and C=O vibrational modes play an essential role on determination of biological structure and dynamics. However, due to the weakness of the C–H absorption and strong absorption of the C=O vibrational band make such experiments less straightforward than those with transitions of nearly the same strength. In this communication the characteristics of the C–H and C=O coupling has been studied using dual frequency two dimensional infrared spectroscopy. 2-Pyrrolidinone has been used as a model molecule of biological system. The coherent and incoherent couplings between C–H and C=O vibrational bands have been observed. The cross peaks dynamics have been discussed and time constant of the cross peak intensity has been calculated.
关键词： dual frequency,vibrational coupling,vibrational spectroscopy,Molecular structure,2DIR spectroscopy,vibrational dynamics
更新于2025-09-12 10:27:22
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Study on Solvent Effect and Estimation of Dipole Moments of Laser Dye 3ADHC
摘要： In this paper solvent effect of 3-acetyl-7-(diethylamino)-2H-chromen-2-one (3ADHC) dye molecule have been studied by solvatochromic shift method. The electronic absorption and emission spectra of the dye molecule were recorded in a variety of polar protic and polar aprotic solvents at room temperature (298K). Solvatochromic shifts, specifically bathochromic (red) shifts were observed in the absorption and emission spectra as a result of solvent polarity, it signifies the π→π* transition involved. The ground state dipole moment and excited state dipole moment of 3AHDC is calculated using solvent correlation methods. Obtained results are in good agreement with the ground state dipole moment calculated by Gaussion computational methods. The ground and excited state dipole moment of the 3ADHC have also been computed from ab initio calculations and compared with those determined experimentally. It has been found that excited-state dipole moment (μe) is greater than ground-state dipole moment (μg) for the title molecule. The increase in dipole moment in the excited singlet states ranges between 3.93 to 8.60D for 3ADHC. This demonstrates that test molecule is more polar in excited states than in ground states for all the solvents used. The spectral changes were analyzed by Kamlet-Taft parameters.
关键词： Stokes shift,Solvatochromic,Molecular Structure of 3-acetyl-7-(diethylamino)-2H-chromen-2-one (3ADHC),Ground state and excited state dipole moment
更新于2025-09-12 10:27:22
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Engineering Charge-Transfer States for Efficient, Low-Energy-Loss Organic Photovoltaics
摘要： Charge transfer (CT) between donors and acceptors following photoexcitation of organic photovoltaics (OPVs) gives rise to bound electron–hole pairs across the donor–acceptor interface, known as CT states. While these states are essential to charge separation, they are also a source of energy loss. As a result of reduced overlap between electron and hole wavefunctions, CT states are influenced by details of the film morphology and molecular structure. Here, we describe several important strategies for tuning the energy level and dynamics of the CT state and approaches that can enhance their dissociation efficiency into free charges. Furthermore, we provide an overview of recent physical insights into the key parameters that significantly reduce the Frenkel-to-CT energy offset and recombination energy losses while preserving a high charge-generation yield. Our analysis leads to critical morphological and molecular design strategies for achieving efficient, low-energy-loss OPVs.
关键词： molecular structure,energy loss,organic photovoltaics,charge transfer states,film morphology
更新于2025-09-12 10:27:22
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Improved molecular structure retrieval method for photoelectron holography
摘要： Photoelectron holography is a method that retrieves molecular structure information from photoelectron diffraction patterns generated by x-ray free-electron lasers, which have the promise of following dynamic molecular structure evolutions with angstrom spatial and femtosecond temporal resolutions (the so-called molecular movie). However, an additional phase is introduced when the photoelectron is scattered by an atom, and this scattering phase turns into a spatial error when the position of the atom is retrieved using a Fourier-type transform. We propose a method to remove, or greatly suppress, this error, with demonstrations using numerical examples.
关键词： x-ray free-electron lasers,Fourier-type transform,molecular structure retrieval,scattering phase,photoelectron holography
更新于2025-09-12 10:27:22
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Temperature Dependence in the NEXAFS Spectra of <i>n</i> -Alkanes
摘要： The Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of orthorhombic single crystals of n-octacosane (n-C28H58), recorded at room temperature (298 K) and at cryogenic temperatures (93 K), show distinct differences. The characteristic carbon 1s → σ*C-H band in the NEXAFS spectrum of n-C28H58 is broader and has a lower energy onset in its room temperature spectrum than in its NEXAFS spectrum recorded at cryogenic temperatures. Density functional theory simulations show that nuclear motion and molecular disorder contribute to the observed spectral broadness and are the origin of the low-energy onset of the C-H band in the room temperature spectrum.
关键词： Temperature Dependence,Quantum Chemistry,n-Alkanes,NEXAFS,Molecular Structure,Spectroscopy
更新于2025-09-11 14:15:04
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Low-Temperature Effect on the Electronic Structure and Spectral-Fluorescent Properties of Highly Dipolar Merocyanines
摘要： Absorption and fluorescence spectra of a vinylogous series of reversely solvatochromic merocyanines based on benzimidazole and malononitrile have been studied in frozen ethanol solutions at 77 K. It is found that they possess negative thermochromism – in contrast to both positively solvatochromic merocyanines and negatively solvatochromic symmetrical ionic polymethines – and even stronger negative thermofluorochromism. It has been deduced from the spectral data, that at low temperature their electronic structure becomes more dipolar, deviating substantially from the virtual ideal polymethine in both the ground and excited states. At that, owing probably to high polarity and ordering of frozen ethanol, the dipolarity of the studied merocyanines increases with the polymethine chain lengthening – the tendency not observed for them in common solvents. The conclusions, based on the spectra data analysis, have been verified by the (TD)DFT–PCM simulations of the dyes within the four-level scheme of electronic transitions.
关键词： Low-Temperature Effect,Spectral-Fluorescent Properties,Merocyanines,Quantum Chemistry,Electronic Structure,Molecular Structure,Spectroscopy
更新于2025-09-10 09:29:36
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Thermally Induced Protonation of Conducting Polyaniline Film by Dibutyl Phosphite Conversion to Phosphate
摘要： The blue thin polyaniline base film changes its color to green after immersion of the film into dibutyl phosphonate. The green color of the film converts to a greenish-blue after heating up to 200 °C in air which is characteristic for protonated conducting form of polyaniline. This is in the contrast to the “standard” polyaniline hydrochloride which is transformed into a crosslinked polyaniline base under such conditions. To explain this unexpected observation, the interaction of polyaniline base with dibutyl phosphonate at ambient conditions and after heating to 200 oC was studied using UV–visible, FTIR and Raman spectroscopies. Based on these studies, we propose that dibutyl phosphite tautomeric form of dibutyl phosphonate which interacts with polyaniline base at 20 °C converts to the oxidized form, dibutyl phosphate, at 200 °C and subsequently protonates the film. Quantum-chemical modelling of the interaction of polyaniline base with dibutyl phosphite and dibutyl phosphate supports this explanation.
关键词： Thermally Induced Protonation,Quantum Chemistry,Conducting Polyaniline Film,Dibutyl Phosphite,Molecular Structure,Phosphate Conversion,Spectroscopy
更新于2025-09-10 09:29:36
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Molecular structure characterization of middle-high rank coal via XRD, Raman and FTIR spectroscopy: Implications for coalification
摘要： In recent years, the major coal producing areas in China have entered the period of deep mining, with coal rank changing from low-rank coal (LRC) to middle-high rank coal (MHRC). Even though material properties of MHRC, such as pore size and shape, have attracted increasing attentions, its molecular structures still remains unclear. This study probes molecular structural properties of five MHRC samples using X-ray diffraction (XRD), Raman and Fourier transform infrared (FTIR) spectroscopy. Test results show that with the deepening of coalification, the aromatic rings of MHRC increase gradually. The aliphatic side chains between the aromatic rings continuously fall off. The ordered structure of coal continues to enhance, resulting in an increase in the degree of graphitization of coal. The average lateral sizes (La), stacking heights (Lc) and interlayer spacing (d002) of the crystallite structures of MHRC samples derived from the XRD range from 20.65 to 31.68, 10.62 to 19.21 and 3.42 to 3.66 ?, respectively. The La values derived from the Raman spectra using the classical linear relationship between 1/La and the ID1/IG band ratio are higher (36.36–59.91 ?) than the values obtained from XRD. The FTIR spectra reveals that MHRC samples contain aliphatic functional groups such as eCH2 and eCH3, aromatic functional groups such as C]C and aromatic ring eCH, and oxygen-containing functional groups such as eOH, C]O and CeO. The aromaticity (fa) of the coal samples determined by FTIR ranges from 0.66 to 0.98, and compared with the fa valued from XRD (0.63 to 0.93), which shows that the MHRC contains abundant of aliphatic components. On the basis of these results, the structural parameters obtained by different spectral techniques are also used to comparatively study the effects of coalification on the molecular structure of coals. The structural parameters of coal derived by these methods reflect the coalification jumps at Ro = 0.5, 0.7–0.9, 1.2, 2.6, 3.3, 3.5–4.0 and 4.2–4.8%. Among them, the jump at Ro = 4.2–4.8% is unreported in previous studies and should be further studied in subsequent research. The application range of structure parameters used to evaluate the coal rank such as d002, La (XRD), fa and G-D1 should be considered because of coalification jumps. The parameters such as 'C', ID1/IG and La (Raman) are better choices for evaluating coal rank for their better correlation with Ro. It is worth pointing out that these parameters have implications for coalification and should be concerned in further study.
关键词： FTIR,Molecular structure,Raman,Coalification jump,Middle-high rank coal,XRD
更新于2025-09-10 09:29:36