Distribution Of Energy Levels Research Articles

Deuteration-Induced Energy Level Structure Reconstruction of Carbon Dots for Enhancing Photoluminescence.

Constrained by a limited understanding of the structure and luminescence mechanisms of carbon dots (CDs), achieving precise enhancement of their photoluminescence (PL) performance without altering the emission wavelength and color remains a challenge. In this work, a deuterated CD is first achieved by simply replacing the reaction solvent from H2O to D2O. The substitution of D atoms for H atoms is not limited on the surface but also within the internal structure of CDs. Deuteration affects the formation of the π-conjugated network structure by altering the content of sp2 carbon and sp3 carbon, ultimately inducing a reconstruction for energy level structure of CDs. Both the intrinsic state and surface state emission, including quantum yield, emission intensity and lifetime, are significantly enhanced after deuteration. It benefits from the reduction in non-radiative transitions, since the lowered vibrational frequencies of D atoms and optimized local energy level distribution in CDs structure. The deuterated CDs are applied in the fabrication of white-light-emitting diodes to show their application potential. This work provides a highly versatile route for improving and controlling photoluminescence performance of CDs and has opportunities to guide the development of CDs for practical applications.

Dependence of the Spill Back Effect on the Energy Level Distribution of Interface States Under the Transfer Gate in CMOS Image Sensor

Dependence of the Spill Back Effect on the Energy Level Distribution of Interface States Under the Transfer Gate in CMOS Image Sensor

Unraveling two yellow fluorescence emission mechanisms and color-changing afterglow characteristics of Dy-doped Mg2SnO4 luminescent materials

In this work, Dy ion doped Mg2SnO4 (Mg2SnO4:Dy3+) with monochromatic yellow fluorescence and color-changing long afterglow properties are prepared by the high-temperature solid-phase method. Mg2SnO4:Dy3+ shows the best luminescence performance under the preparation conditions of 1550 °C and 0.02 Dy3+ concentration. The samples are able to achieve yellow fluorescence emission (λem = 575 nm) under 350 nm and 291 nm excitation, and the emission intensity of the samples under 350 nm excitation is much higher than that of 291 nm excitation. Under 254 nm excitation, the sample not only emits bright white fluorescence but also has the ability of obvious afterglow after excitation. Moreover, the afterglow also has the color change function of transition from bright white to yellow. The luminescence mechanism study shows that Mg2SnO4:Dy3+ contains two emission centers, Dy3+ and lattice defects. Combining the results of spectroscopic measurements with the Dy3+ energy level distribution data, two different fluorescence emission processes under 291 and 350 nm excitation as well as the afterglow discoloration mechanism due to 254 nm excitation are discussed in detail.

Theoretical insights into narrow bandgap CuFeS2 chalcopyrite for thermophotovoltaic applications

CuFeS2 chalcopyrite compound with a parochial direct band-gap of 0.55 eV could be a potential candidate for thermophotovoltaic (TPV) cells. In this paper, a theoretical analysis has been performed on CuFeS2 compound utilizing density functional theory (DFT) to reveal its suitability in TPV applications. The configuration of electrons and their distribution of energy levels indicate the semiconducting nature of the compound. Then, CuFeS2 based single p-n junction TPV cell has been designed and simulated based on the transport equation of the semiconductor device model. The CuFeS2 thermophotovoltaic shows a 5% efficiency achieved with a VOC of 0.261 V, JSC of 10.90 A/cm2, and a fill factor (FF) of 69.49% at a black body temperature (TBB) of 1625 K. The findings can provide valuable insights for producing cost-effective CuFeS2 thermophotovoltaic systems.

A benzobisoxazole-based polymer assisting high efficiency polymer solar cells

Ternary strategy is an effective method to optimize photovoltaic process and improve device performance. In this work, a benzobisoxazole-based conjugated polymer PBBO was designed and employed as the guest component for PM6:BTP-eC9 based devices. The polymer PBBO shows a large band gap of 2.16 eV and strong photoluminescence property, with efficient energy transfer observed between PBBO and PM6. The ternary blends not only form a cascaded energy level distribution, but also an alloy-like structure, which can effectively promote the exciton dissociation, charge transfer and efficiently suppress charge recombination. As a result, the power conversion efficiency (PCE) of the ternary device is substantially improved from 17.50% to 18.66% with the incorporation of PBBO guest component. Meanwhile, the ternary device shows good stability with retaining 86% of initial efficiency after storage for 2000 hours. This research demonstrates that the polymer PBBO would be an excellent photovoltaic material to optimize the performance of polymer solar cells.

Impact of alloy‐like phase on energy loss mitigation in multi‐component organic photovoltaics

AbstractThe multi‐component strategy has proven effective in advancing the performance of organic photovoltaics (OPVs), enhancing photocurrent and fill factor through spectral complementarity and morphology optimization. However, the open‐circuit voltage (VOC) mechanism in multi‐component systems lacks systematic investigation. In this study, we explore the influence of alloy‐like phases on energy level distribution and energy loss mechanisms in multi‐component OPVs. Appropriate modulation of donor alloy‐like phases maintains the original intermolecular stacking, enhances component compatibility, reduces acceptor aggregation, and improves acceptor phase purity, mitigating non‐radiative recombination losses. Additionally, suitable alloy‐like phase modulation elevates charge transfer (CT) states, reducing the gap between CT and local exciton state, lowering reorganization energy, and alleviating radiative recombination loss below the bandgap. Through synergistic optimization (layer‐by‐layer method with solid additive), ternary devices based on Y6 acceptor achieve a notable 19.41% power conversion efficiency, offering new insights for the analysis of the energy loss of the multi‐component OPVs.

Exploring the Regulatory Mechanism of ZnS Materials under Stress and Re Doping: Insights from Density Functional Theory

The application prospects of ZnS stress luminescent materials cover many fields such as high‐precision structural monitoring, smart materials, biomedical imaging, and new sensor technologies, which bring broad application prospects and significance to them in the fields of engineering, medicine, and scientific research. In this article, the electronic structure and optical properties of ZnS materials are successfully regulated by applying pressure and doping rare earth metals (Re), and it is found that the regulation of the luminescence properties of ZnS is the result of stress and doping interactions. Specifically, when pressure is applied or Re metal doping, the lattice structure is deformed and the atomic spacing is adjusted, which affects the electronic energy level distribution and optical properties of ZnS materials. Computational analysis of density functional theory (DFT) reveals the microscopic mechanisms behind these changes, including changes in lattice parameters, adjustment of bond length, and changes in band structure. This study provides theoretical guidance for the design and synthesis of high‐performance and high‐stability ZnS light‐emitting materials, and is of great significance for expanding the application of ZnS in the field of lasers and sensors.

Molecular Design for Vertical Phase Distribution Modulation in High-Performance Organic Solar Cells.

Component distribution within the photoactive layer dictates the morphology and electronic structure and substantially influences the performance of organic solar cells (OSCs). In this study, a molecular design strategy is introduced to manipulate component and energetics distribution by adjusting side-chain polarity. Two non-fullerene acceptors (NFAs), ITIC-16F and ITIC-E, are synthesized by introducing different polar functional substituents onto the side chains of ITIC. The alterations result in different distribution tendencies in the bulk heterojunction film: ITIC-16F with intensified hydrophobicity aligns predominantly with the top surface, while ITIC-E with strong hydrophilicity gravitates toward the bottom. This divergence directly impacts the vertical distribution of the excitation energy levels, thereby influencing the excitation kinetics over extended time periods and larger spatial ranges including enhanced diffusion-mediated exciton dissociation and stimulated charge carrier transport. Benefitting from the favorable energy distribution, the device incorporating ITIC-E into the PBQx-TF:eC9-2Cl blend showcases an impressive power conversion efficiency of 19.4%. This work highlights side-chain polarity manipulation as a promising strategy for designing efficient NFA molecules and underscores the pivotal role of spatial energetics distribution in OSC performance.

Research on molecular dynamics and electrical properties of high heat-resistant epoxy resins.

In order to prepare highly heat-resistant packaging insulation materials, in this paper, bismaleimide/epoxy resin (BMI/EP55) composites with different contents of BMI were prepared by melt blending BMI into amino tetrafunctional and phenolic epoxy resin (at a ratio of 5:5). The microstructures and thermal and electrical properties of the composites were tested. The electrostatic potential distribution, energy level distribution, and molecular orbitals of BMI were calculated using Gaussian. The results showed that the carbonyl group in BMI is highly electronegative, implying that the carbonyl group has a strong electron trapping ability. The thermal decomposition temperature of the composites gradually increased with the increase of BMI content, and the 20% BMI/EP55 composites had the highest heat-resistance index, along with a glass transition temperature (Tg) of >250°C. At different test temperatures, with increase in the BMI content, the conductivity of epoxy resin composites showed a tendency to first decrease and then increase, the breakdown field strength showed a tendency to first increase and then decrease, and the dielectric constant was gradually decreased. Two trap centers were present simultaneously in the composites, where the shallow trap energy level is the deepest in 20% BMI/EP composites and the deep trap energy level is the deepest in 10% BMI/EP55 composites. Correspondingly, the 10% BMI/EP55 composite had a slower charge decay rate, while the 20% BMI/EP55 had a faster charge decay rate. In summary, the BMI/EP55 composites with high heat resistance and insulating properties were prepared in this study, which provided ideas for preparing high-temperature packaging insulating materials.

Theoretical Spectroscopic Study of Isopropyl Alcohol (CH3-CHOH-CH3)

Accurate spectroscopic parameters of isopropyl alcohol, a volatile organic compound present on Earth and in extraterrestrial atmospheres, are provided. The work pursues the study of the far-infrared region, describing the distribution of the low-lying vibrational energy levels that can be populated at very low temperatures, having effects on the detectability and identification. The potential energy surface shows 27 almost equivalent minima producing 27 subcomponents of the levels due to tunneling effects. Computations have been performed using highly correlated ab initio calculations, accurate enough to distinguish between the rotational parameters of the two quasi-identical conformers gauche and trans. A variational procedure in three dimensions depending on three interacting internal rotations, the internal rotation of the two methyl groups and the internal rotation of the hydroxyl group, is employed to compute the energies. The 27 subcomponents of the ground vibrational state can be grouped into three series of nine energy levels located around 0.000, 1.693, and 81.927 cm−1 whose energy difference is due to the OH torsion effect. The nine subcomponents integrated in each series derive from the torsion of the two methyl groups. The computations reproduce accurately the available experimental data. New predicted properties can help the spectroscopic analysis of the rotational-vibrational spectra in the gas phase and further detections of vibrationally excited isopropyl alcohol.

Construction of a highly reactive Zn/NiCo2O4 surface and analysis of its antimicrobial properties

By incorporating Zn into NiCo2O4, a rod-shaped Zn/NiCo2O4 nanocomposite with an increased number of active sites on its surface was constructed in this study. The antimicrobial activity of this material against Escherichia coli was investigated, revealing a significant improvement compared to pure NiCo2O4 under both dark conditions and light irradiation, with an increase in the antimicrobial rate from 45.71 % to 99.06 % and 51.48 %–88.13 % at a dosage of 0.1 mg/mL, respectively. This enhancement can be attributed to the increased formation of oxygen vacancies on the material surface after Zn doping. These vacancies lead to greater exposure of high-valence metal active sites and enhanced redox reactions. Additionally, introducing defects improves the energy level distribution, resulting in a stronger reduction ability at the conduction band position. Consequently, the generation of reactive oxygen species increases, enhancing both contact sterilization and photocatalytic sterilization. Furthermore, Zn/NiCo2O4 demonstrated excellent cyclic stability, maintaining an antibacterial rate of up to 95.13 % after five cycles of antibacterial activity. In conclusion, the use of this material is not restricted to light conditions, and the addition of Zn greatly enhances its antibacterial effectiveness. This study demonstrates that Zn/NiCo2O4 has significant potential for applications in the field of antibacterial materials.

Numerical study on the non-equilibrium characteristics of high-speed atmospheric re-entry flow and radiation of aircraft based on fully coupled model

The strong coupling interactions of non-equilibrium flow, microscopic particle collisions and radiative transitions within the shock layer of hypersonic atmospheric re-entry vehicles makes accurate prediction of the aerothermodynamics challenging. Therefore, in this study a self-consistent non-equilibrium flow, collisional–radiative reactions and radiative transfer fully coupled model are established to study the non-equilibrium characteristics of the flow field and radiation of vehicle atmospheric re-entry. The comparison of the present calculation results with flight data of FIRE II and previous results in the literature shows a reasonable agreement. The thermal, chemical and excited energy level non-equilibrium phenomena are obtained and analysed for the different FIRE II trajectory points, which form the critical basis for studying the heat transfer and radiation. The non-equilibrium distribution of excited energy levels significantly exists in the post-shock and near-wall regions due to the rapid vibrational dissociation and electronic under-excitation, as well as the wall catalytic reactions. The analysis of stagnation-point heating of FIRE II illustrates that the translational–rotational convection and the dissociation component diffusion play key roles in the aerodynamic heating of the wall region. The spectrally resolved radiative intensity in the entire flow field indicates that the vacuum ultraviolet radiation caused by the high-energy nitrogen atomic spectral lines makes the main contribution to the radiative transfer. Finally, it is found that the non-equilibrium flow–radiation coupling effect can exacerbate the excited energy level non-equilibrium, and further affect the gas radiative properties and radiative transfer. This fully coupled study provides an effective method for reasonable prediction of atmospheric re-entry flow and radiation fields.

Perturbations on Oxybiotin Leading to Biotin. A DFT Treatment

In the present computational study, conversion of oxybiotin to biotin by means of oxygen to sulfur replacement has been investigated within the restrictions of density functional theory at the level of B3LYP/6-31++G(d,p). Both of the molecules have not only exothermic heat of formations but also favorable Gibbs free energy of formation values at the standard state. They are electronically stable. Various quantum chemical data accompanying the perturbation considered have been collected and discussed including UV-VIS spectra. The oxygen to sulfur replacement highly affects not only the distribution of molecular orbital energy levels but also the energies of the molecular orbitals in such a way that going from oxybiotin to biotin the HOMO energy level raises up but the LUMO decreases. The both occur at unequal extents thus biotin exhibits some bathochromic effect compared to oxybiotin.

Assessing the Effect of Electronic Pseudopotentials and Relativistic Treatments on the Structural and Electrical Properties of GaN: A DFT Study

Applying the principle of Density functional theory, we can calculate various parameters like lattice constant, band gap, band plot, dielectric function plot, refractive index plot, conductivity plot, density of state plot, loss function etc. of GaN. In this work, we use different electronic pseudopotentials with different relativistic treatment studied using Local density approximation functional (LDA-CAPZ) within DFT for GaN. We used to calculate the energy values, lattice parameters change after geometry optimisation and plot the band energies. Electronic structure calculations results are compares taking different electronic pseudopotentials of different cut-off energy having different relativistic approaches. The Density of state plot and partial density of states plot help to studied more about the electronic as well as magnetic characteristics of the GaN sample. Here, we also compare the advantages and disadvantages of different pseudopotentials with different relativistic approaches of the sample. Energy level distribution and partial density of states were compared for all the pseudopotentials with different relativistic treatments, providing insight into the orbital contributions of electrons to the density of levels. Our study provides a deeper understanding into the impact of electronic pseudopotentials and relativistic treatments on the electronic and structural properties of GaN.

A novel graphitic carbon nitride photocatalyst with ultramicro amounts of intramolecular donor-acceptor structures for excellent photocatalytic hydrogen production

In this study, facile supramolecular thermal polymerization was employed for an attempt to modify graphitic carbon nitride (g-C3N4) using ultramicro amounts of diphenylamino-4-benzaldehyde as the dopant, and melamine and cyanuric chloride as the raw materials. The reaction of aldehyde-amine achieved diphenylamino-4-benzaldehyde grafting onto the edge of the heptazine ring of g-C3N4, resulting in the formation of a novel g-C3N4 with intramolecular twisted donor–acceptor (D-A) structures known as CN-Dxmg. It was confirmed that addition of 2 mg (0.67 wt‰) of diphenylamine-4-benzaldehyde as the donor regulated the energy level distribution of CN-D2mg, and as-obtained intramolecular D-A structures can promote the photogenerated carrier separation and migration of CN-D2mg through a directional channel for electron transfer from diphenylamine-4-benzaldehyde to heptazine. The results indicate that CN-D2mg photocatalyst has a high hydrogen production rate of 14581.1 μmol·h−1·g−1 at 420 nm under visible light irradiation, which is 1.6 times higher than that of pristine g-C3N4. The study presents an effective approach for large-scale applications involving g-C3N4 photocatalyst in clean energy production.

Modification Study on Quantum Tunneling Radiation of Kinnersley Black Hole

In the spacetime of a linearly accelerating Kinnersley black hole, the Lorentz-breaking theory is used to modify the dynamical equations of Dirac particles by selecting gamma matrices and aether-like field vectors in the curved spacetime of this black hole. Using the WKB approximation and black hole quantum tunneling radiation theory, we investigate the characteristics of quantum tunneling radiation in this black hole.By solving the modified spinor field equations, we obtain expressions for the corrected quantum tunneling rate, Hawking temperature, and surface gravitation of the black hole. By studying the particle radial component of the general momentum in this curved spacetime, a new expression for the modified distribution of positive and negative energy levels of Dirac particles, as well as their maximum value of crossing energy level, is obtained. In order to further elucidate the physical significance of the research methodology employed in the article and a series of conclusions obtained, a detailed discussion of the corresponding results is provided in the later sections of this paper.

Specific heat of a driven lattice gas

Calorimetry for equilibrium systems aims to determine the available microscopic occupation and distribution of energy levels by measuring thermal response. Nonequilibrium versions are expected to add information on the dynamical accessibility of those states. We perform calculations on a driven exclusion process on an array of particle stations, confirming that expectation. That Markov model produces a fermionic nonequilibrium steady state where the specific heat is computed exactly by evaluating the heat fluxes that are entirely due to a change in ambient temperature. We observe a zero-temperature divergence (violation of the Third Law) when the Fermi energy and the kinetic barrier for loading and emptying become approximately equal. Finally, when the kinetic barrier is density-dependent, a stable low-temperature regime of negative specific heat appears, indicating an anti-correlation between the temperature–dependence of the stationary occupation and the excess heat.

Crystal growth, HOMO-LUMO engineering and charge-transfer emission of TCNB-based donor-acceptor cocrystals

Using carbazole (CARB), dibenzothiophene (DBZP) and dibenzofuran (DBZF) as electron donors, 1,2,4,5-tetracyanobenzene (TCNB) as electron acceptor, three typical types of luminescent organic cocrystals were synthesized by a simple supramolecular assembly strategy. The cocrystals exhibit interesting optical properties for its charge transfer (CT) interactions. Meanwhile, a series of three-component (CARB)x (DBZP)1-x (TCNB) crystalline microtubes comprising organic CT interactions have been prepared by the self-assembly with poor solvent co-precipitating method. DFT calculations were used to predict the CT interactions and the binding patterns of donor and acceptor, which suggest that the CT interactions can largely influence the energy level and orbital distributions. Moreover, the SXRD analyses verified the cocrystals are constructed by π-π stacking with a face-to-face model. The solid-state cocrystals and microtubes were well characterized by PXRD, UV absorption spectra, emission spectra, fluorescence lifetime and quantum yield analyses. The obvious red-shift in UV–vis absorption spectra and emission spectra with respect to the free monomer indicate the formation of CT interactions. The emission colors of the mixed microtubes can be tailored from green to orange as well as associated photophysical properties with the increasing of dopant concentrations. Therefore, by the combination of experimental and theoretical studies on the cocrystals and microtubes, this work not only reports the new types of crystalline micro-nano materials, but also provides an in-depth understanding of the relationship between structure and fluorescence effect.

Investigation on the kinetics of a diode-pumped plasma-jet type metastable argon laser

Diode-pumped rare gas lasers (DPRGLs) have the potential for high-energy laser output with high beam quality. The metastable concentration >1014 cm−3 and pump intensity >10 kW/cm2 are required in developing high-power and efficient DPRGLs. However, the kinetics of 1s and 2p levels (Paschen notation) under these conditions is unclear yet, particularly regarding the adverse effects of interference energy levels (e.g., 1s4 and 2p1–2p8). This study addresses this gap by measuring the number densities of 1s and 2p levels in a diode-pumped plasma jet metastable argon laser. The experiment was conducted with a much higher number density of 1014 cm−3 and a higher pump intensity of 12 kW/cm2 than our previous works. The results indicate that the adverse effect of 1s4 accumulation could be partially compensated, and the relative population distribution of 2p energy levels remained unchanged. However, the high gas temperature (>1000 K) caused a significant negative impact of high 2p levels (2p1–2p8), and the air environment weakened the effect of He collision relaxation.

Design and Numerical Investigation of CsPbI3/CsSn0.5Ge0.5I3 Double‐Absorption‐Layer Heterojunction Perovskite Solar Cells Based on SCAPS‐1D

CsPbI3 material has obvious advantages in constructing stable all‐inorganic perovskite solar cells (PSCs). However, the wide bandgap (1.73 eV) of CsPbI3 cannot effectively absorb low‐energy photons, which seriously hinders its development in single‐junction solar cells. In this study, a CsPbI3/CsSn0.5Ge0.5I3 double‐absorption‐layer heterojunction PSC is constructed by SCAPS‐1D. In the results, it is shown that adding a narrow bandgap CsSn0.5Ge0.5I3 absorption layer optimizes the band structure and energy level distribution, enhancing the device's built‐in potential and spectral absorption range. The combination of different electron‐transport layers, hole‐transport layers, and perovskite layers are stimulated, ultimately identifying the optimal material for the charge‐transport layers. In addition, the effects of internal factors (thickness and defect density of the absorption layer, interface defects, and work function of the back electrode) and ambient temperature on the overall performance of the device are investigated. The optimized power conversion efficiency of the device (fluorine‐doped tin oxide/Cd0.5Zn0.5S/CsPbI3/CsSn0.5Ge0.5I3/Cu2BaSnS4/Au) reaches 31.02%. In this study, a new attempt at the construction of stable and efficient all‐inorganic heterojunction PSC is provided.