Dielectric Coefficient Research Articles

DFT study of optoelectronic and thermoelectric properties of pure and doped double perovskite Cs2SnI6 for solar cell applications

The global need of energy is raising day by day. To meet this demand double perovskites (DPs) can play a vital role for energy conversion devices. In this letter, we formulated and examined lead-free defect perovskites using a combination of tellurium and tin, denoted as Cs2Sn1-xTexI6 (0, 0.25), utilizing density functional theory which include structural, optical and thermal behavior. Both the optimized volume and lattice parameter exhibit a linear increase with the Te content in Cs2Sn1-xTexI6 (CsSnTeI). The negative value of formation energy for both pure and doped materials along with their Poisson and Pugh ratio confirm the stability of these materials. The band structure analysis reveals its semiconducting behavior, with the band gap expanding proportionally to the increased Te concentration with band gap value of pure (1.20 eV) and doped 91.43 eV) double perovskites. Optical characteristics, including the dielectric function and absorption coefficient, were also analyzed. To expose their potential use of Cs2Sn1-xTexI6 (0, 0.25) in thermoelectric devices, temperature dependent thermoelectric features are investigated reveal that suitability of these materials for energy conversion purposes.

Strain-incorporated structural, electronic, and dielectric properties of cubic FAPbCl3 perovskites together with the spin-orbit coupling

The organic-inorganic perovskite materials have garnered significant interest in solar technology because of their impressive structural, electrical, and optical characteristics. This study investigated the effects of hydrostatic strains (tensile and compressive) on the structural, electronic, and optical properties and the influence of spin-orbit coupling (SOC) on the electronic properties of formamidinium lead chloride cubic (FAPbCl3) perovskite structures employing first-principles density-functional theory (DFT). FAPbCl3 without SOC showed a semiconductor perovskite structure with a direct bandgap of 2.767 eV. Compressive strain (-8–0 %) reduced bandgaps, but tensile strain only increased them by +2 %. The SOC significantly reduced the bandgap by ∼1 eV, shifting it from direct to indirect. The analysis showed that neither of compressive or tensile strains can affect the system's semiconductiveness nature under the studied strain range. The dielectric function, loss spectrum, and absorption coefficient peaks of FAPbCl3 perovskites display a blueshift under compressive strains and a redshift under tensile strains. This material can be used in solar cells, lasers, and light detectors because of its promising electrical and optical properties.

Ab initio Investigation of quasi-one-dimensional ternary chalcogenides Sr2ZnX3 (X = S, Se, Te) for efficient photovoltaic and thermoelectric applications

The quest for sustainable and renewable energy sources has become a vital global mission. Transition metal chalcogenide materials have garnered significant attention due to their unique low-dimensional physical properties. In this work, we explore the impact of ionic radius in modulating the physical properties of ternary chalcogenides by calculating structural, electronic, optical, and thermoelectric properties of Sr2ZnX3 (X = S, Se, Te) materials using first-principles density functional theory (DFT) as implemented in the WIEN2k program. To evaluate the effect of ionic radius, two novel semiconductors Sr2ZnSe3 and Sr2ZnTe3, were constructed using similar isostructural material Sr2ZnS3. Further optimized structure reveals that the corner-sharing ZnX4 tetrahedra extended along the b-axis confirms the quasi-one-dimensional (Q1D) nature of Sr2ZnX3 materials. Band structure analysis revealed a wide direct bandgap nature with the values of Sr2ZnS3 (3.4 eV), Sr2ZnSe3 (2.8 eV) and Sr2ZnTe3 (1.75 eV), respectively. The lower effective mass of electrons and holes suggests higher carrier mobility and charge recombination rates, vital for photovoltaic applications. The optical properties of the materials are studied in the energy range of 0–10 eV (IR–Vis–UV region). We found that Sr2ZnTe3 material exhibits higher values of dielectric function, absorption coefficient (α≈106 cm−1), refractive index, and lower reflectivity, which indicates its suitability for photovoltaic application. Thermoelectric properties are crucial for assessing material utility in thermoelectric applications, and the study revealed substantial values of the Seebeck coefficient, electrical conductivity, figure of merit (ZT) greater than 2, power factor, and lower electronic thermal conductivity. The studied properties signify Sr2ZnX3 materials as potential candidates for light-emitting semiconductors and thermoelectric applications.

Understanding of the correlation of structural and microwave dielectric performance of (1-x)MgTiO3 - xCaTiO3 ceramics for dielectric resonator antenna applications

In this article, the effect of CaTiO3 on the structural and microwave dielectric characteristics of MgTiO3 has been discussed. The (1-x)MgTiO3 - xCaTiO3 (abbreviated as (1-x)MT- xCT) for x = 0.025, 0.05, 0.075, 0.1 ceramics have been developed using a solid-state reaction route. The structural as well as morphological characteristics of specimens have been observed by employing X-ray diffraction and scanning electron microscope methods. The Rietveld refinement technique of X-ray diffraction data have been conducted for the refinement of structural phases. It suggests that two crystallographic phases have been present in all materials. The SEM images display dense well-identified grains of (1-x)MT - xCT (for x = 0.025–0.1) ceramics. The Raman spectroscopy method has been employed to detect the symmetry of ceramics and modes of vibration of the materials. The microwave dielectric characteristics like dielectric permittivity (εr), loss (tanδ), quality factor (Q×f), and temperature coefficient at resonant frequency (τf) of (1-x)MT - xCT (for x = 0.025–0.1) ceramics have been thoroughly investigated. The bond strength, bond valency, bond energy, and tolerance factor of (1-x)MT - xCT (for x = 0.025–0.1) materials have been evaluated and their relation with microwave dielectric characteristics has been discussed. The (1-x)MT - xCT (for x = 0.025–0.1) ceramics show excellent dielectric properties with near to zero τf. In addition, DRAs have been designed with (1-x)MT - xCT (for x = 0.025–0.1) materials as dielectric resonators and various antenna properties have been studied with the help of HFSS software. This work suggests that (1-x)MT - xCT for (x=0.05) material can be a promising candidate for DRA applications working in the C band.

Investigating the physical characteristics and photovoltaic performance of inorganic Ba3NCl3 perovskite utilizing DFT and SCAPS-1D simulations

Lead-free inorganic cubic halide perovskites exhibit outstanding physical properties in solar technology. Ba3NCl3 emerges as a promising absorber material in solar cells. Utilizing first-principles density-functional theory (FP-DFT), we thoroughly analyzed Ba3NCl3 properties. It exhibits mechanical, dynamically stability and natural ductility. Electron charge distributions indicate significant ionic bonding between Ba and Cl, and covalent bonding between N and Cl. At the Γ-point, the direct bandgap of PBE(HSE) is 0.57 eV (1.20 eV). Dielectric functions, absorption coefficients, and conductivity confirm robust absorption characteristics across the visible-ultraviolet spectrum. SCAPS-1D simulation identified optimal PV parameters for Ba3NCl3-based cells with a WS2 buffer layer, considering various layer thicknesses and doping densities. In an Al/FTO/WS2/Ba3NCl3/Au structure, under ideal conditions, impressive metrics include an open circuit voltage (VOC) of 1.036 V, photocurrent density (JSC) of 38.21 mA/cm2, fill factor (FF) of 80.75 %, and maximum power conversion efficiency (PCE) of ∼ 32 %. Ba3NCl3 shows promise as a potential absorber in hybrid perovskite photovoltaic devices, especially with WS2 electron transport layers.

Exploring the Cs[formula omitted]LiLuCl[formula omitted] elpasolite scintillator for thermal-neutron detection: A comprehensive DFT and TD-DFT studies

In this study, we investigate the halide perovskite material Cs2LiLuCl6 using both density functional theory (DFT) and time-dependent density functional theory (TD-DFT) approaches. Our analysis focuses on the structural, electronic, and optical properties of the material, conducted with the Quantum Espresso code. In order to confirm the structural stability of the material, we performed various tests including analysis of elastic constants, formation energy, tolerance factor, and phonon dispersion. Employing the generalized gradient approximation (GGA) and GGA+U, we determine that the material behaves as an insulator with a direct band gap of 5.3042 eV and 5.4245 eV, respectively. Additionally, DFT+U calculations were performed to study the dielectric function, reflectivity, absorption coefficient, and refractive index, revealing a high transmittance rate exceeding 90%. Under ideal conditions, the upper light yield (LYsc) is estimated to be 75411 ph/MeV and 73739 ph/MeV for the DFT and DFT+U methods, respectively. These results, along with the presence of lithium in Cs2LiLuCl6, highlight its potential for use in scintillation-based thermal-neutron detection applications.

Electronic and optical characteristics of CaLiX3 (X = Cl, Br, I) perovskite compounds using the Tran–Blaha modified Becke–Johnson potential

We present the results of a comprehensive investigation using the full-potential linearized augmented plane wave approach to analyze the structural characteristics, electronic structures, and optical spectra of the perovskite compounds CaLiX3 (X = Cl, Br, or I). Various functionals were employed to simulate the exchange–correlation interactions. The calculated equilibrium structural parameters, obtained using the generalized gradient approximation, are consistent with the existing findings in the literature. The computed electronic structures reveal that the Tran–Blaha modified Becke–Johnson potential significantly enhances the bandgap. For all CaLiX3 compounds studied, we predicted an indirect bandgap. Additionally, we observed a gradual decrease in the bandgap as the atomic size of the X element increases. The electronic states constituting the various energy bands were evaluated by computing the partial and total densities of states. In addition, we computed a variety of optical spectra, including the complex dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity, and electron energy loss function. The results demonstrate that a decrease in the bandgap leads to an increase in the zero-frequency limit of the dielectric function ε(0). The origins of the peaks and structures in the optical spectra were identified.

A DFT investigation on halide double perovskites X2ScTlI6 (X= Rb, Cs) for thermoelectric and optoelectronic applications

The present study conducted by first-principles calculations to explore the physical properties of Rb2ScTlI6 and Cs2ScTlI6 double perovskite compound utilizing the FP-LAPW method within the framework of DFT, as implemented in the WIEN2K software package. The electronic and optical characteristics of double perovskite materials were assessed utilizing the TB-mBJ functional, while the structural properties were analyzed employing the GGA-PBE approximation. Electronic properties demonstrated the semiconducting nature of the materials. Optical properties including the dielectric function, absorption coefficient, and reflectivity were computed, affirming the suitability of the compound for device applications across various spectral regions (infrared, visible, and ultraviolet). Additionally, this research delves into the thermoelectric properties, examining factors such as the ratio of thermal to electrical conductivity, a key metric known as the figure of merit, and the Seebeck coefficient. The study reveals that ZT exhibits higher values at lower temperatures but declines as temperature increases. ZT calculations demonstrate minute variations within 200–800 K and computed parameter values are quite favorable for thermoelectric applications of these materials in the future. Notably, this research contributes novelty by investigating the thermoelectric properties of Rb2ScTlI6 and Cs2ScTlI6 double perovskite, encompassing electrical conductivity, Seebeck coefficient, and the figure of merit.

First principle investigations of opto-electronic and thermoelectric response of A2TlAsX6 (A = K, Rb; X = Cl, Br) compounds

We have investigated the structural, electronic, optical, and thermoelectric behavior of halide-based double perovskites A2TlAsX6 (A = K, Rb; X = Cl, Br) compounds to reveal their potential in various opto-electronic and thermoelectric applications using first-principle calculations. For the computation of the various properties of A2TlAsX6 (A = K, Rb; X = Cl, Br) compounds, we have used approximations available within density functional theory (DFT). The energy bands and density of states have been used to elucidate the electronic response of the studied compounds, while the interpretation of optical properties is presented in terms of dielectric tensor, absorption coefficient, reflectivity, refraction and energy loss spectra. The investigated compounds exhibit a direct band gap within the energy range of 1.36 to 2.24 eV, indicating the promising nature of these compounds for diverse optoelectronic applications. Moreover, thermoelectric properties such as the figure of merit, power factor, Seebeck coefficient, specific heat, electric and thermal conductivity have also been computed for the studied compounds. Our investigation unveils the remarkable optoelectronic characteristics of the studied perovskites, which can be attributed to their advantageous bandgap and highly effective light absorption capabilities. Furthermore, these perovskites showcase exceptional thermodynamic stability, elevated electrical conductivity, favorable figure of merit (ZT) values, and reduced thermal conductivities. These findings suggest their suitability for applications in optoelectronic devices and thermoelectric applications. In this study, it is found that A2TlAsBr6 compounds exhibit significant absorption in the visible spectrum, rendering them more favorable for optoelectronic applications compared to A2TlAsCl6 compounds. Conversely, for thermoelectric applications, the Cl-based perovskites studied show greater promise than their Br-based counterparts. The modified Becke–Johnson (mBJ) potential emerges as the most precise approach for analyzing the electronic, optical, and thermoelectric characteristics of A2TlAsX6 (where A = K, Rb; X = Cl, Br) perovskites, surpassing other approximations utilized in present study.

Unveiling the potential of CuAlxGa1−xSe2 (x = 0.25) chalcopyrite as absorbent for photovoltaic application: first-principles insights into the structural, elastic, mechanical, electronic, thermodynamic and optical properties

This study explores the structural, elastic, mechanical, electronic, and optical properties of CuAlxGa1−xSe2 (x = 0.25) chalcopyrite, a crucial material in photovoltaic cells. Utilizing type II-IV-V2 chalcopyrite, widely employed in high-efficiency solar cell production, we employ first-principles calculations with Tran–Blaha-modified Becke–Johnson exchange potential techniques. We aim to determine the band gap and optical properties to understand the compound’s morphology, crucial for solar cell development. Results show CuAlxGa1−xSe2 as a 1.36 eV direct band gap semiconductor. Optical characteristics, including dielectric tensor components and absorption coefficient, are calculated to assess its suitability for solar cell applications. Predictions of Young’s modulus E, Poisson’s ratio ν, bulk B, and shear G moduli provide insight into the crystal’s mechanical behavior. Additionally, phonon, dynamical stability, and thermodynamic properties are discussed, shedding light on the material’s potential in photovoltaic technology.

Unveiling the electronic, optical, thermoelectric, and magnetic properties of novel Ba2GdMO6 (M = Pa, Ta) via DFT calculation

The optoelectronic, thermoelectric, and magnetic properties of novel Ba2GdMO6 (M = Pa, Ta) double perovskites have been computed with the spin-polarized density functional investigation. The calculations are performed using the FP-LAPW method in Wein2K code, by employing the GGA + U approximations. The band structures and density of states analysis show that Ba2GdPaO6 is an indirect band gap semiconductor with band gap values of 3.0 eV and 3.1 eV in the up and down spin channels, respectively. The Ba2GdTaO6 is also predicted as a semiconducting material with a direct band gap of 2.9 eV and 3.0 eV in up and down spin channels. The optical characteristics of the materials, such as the dielectric constants, absorption coefficient, reflectivity, loss function, and refractive index are computed. The optical results reflect that the materials are excellent choices for high-energy absorbent. The Seebeck coefficient increases beyond the temperature of 300 K for Ba2GdPaO6 and 400 K for Ba2GdTaO6. The increase in the Seebeck coefficient values suggests that these materials are p-type semiconducting. The ferromagnetic nature of the materials has been confirmed by predicting the ferromagnetic phase to be the most stable state. The total magnetic moments of the materials are found equal to 7 µB.

Investigating the optical properties and electronic structure of gallium phosphide nanotubes doped with arsenic via implementing first-principles calculations.

This study investigates the impact of arsenic doping on the optical characteristics and electronic structure of zigzag (8, 0) and armchair (4, 4) gallium phosphide nanotubes using first-principles calculations based on the GaP1-xAsx system, where x = 0, 0.25, 0.5, 0.75, and 1. The electronic calculations showed that doping more arsenic atoms reduces the energy band gap for zigzag and armchair GaPAs nanotubes. PDOS analysis indicates that Ga-4p and P-3p orbitals play a significant role in determining the electronic properties of the GaP nanotube. The dominance of Ga-4p and P-3p orbitals in both the valence and conduction bands indicates their importance across the energy spectrum of the material. The complex dielectric function and absorption coefficient of zigzag and armchair GaP1-xAsx nanotubes are calculated for incident radiation with energies ranging from 1 to 6.2eV. Optical results revealed that both zigzag and armchair GaPNTs exhibit strong absorption in the UV-visible regions due to electronic transitions between different Van Hove singularities. Also, due to quantum confinement effects, pure zigzag gallium phosphide nanotube exhibited two absorption edges at wavelengths (273 and 375nm). These edges stand from the energy level's quantization in the nanotube construction, affecting the absorption characteristics. Substitutional doping by arsenic atoms changes the absorption edge to the long wavelengths due to decreased bandgap energy. Investigating electronic structures and optical properties of nanotubes proposes several advantages, such as understanding the doping effects on the nanotube structure and contributing to the direction of the experimental studies. These computational studies play a key role in developing the applications of nanomaterials. Calculations of density functional theory (DFT) are achieved via the SIESTA package. SIESTA is a powerful and effective tool for executing DFT calculations on a large system of atoms. It generates numerous output files covering detailed information about the electronic structure, optical properties, total energy, optimized geometry, and other computed properties. The generalized gradient approximation GGA with Perdew-Burke-Ernzerhof PBE functional was used. A vacuum region of 10 A0 was applied to avoid the interactions of adjacent nanotubes.

A Comprehensive Density Functional Theory Analysis on Structural, Electronic, and Optical Properties of BiOF

Based on density functional theory (DFT), the electronic, structural, and optical properties of bismuth oxyfluoride (BiOF) are investigated by using various exchange–correlation functionals. The local density approximation (LDA), Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA), Perdew-Burke-Ernzerhof generalized gradient approximation for solids (PBEsol), and Wu-Cohen (WC) functionals are implemented in Wien2k software. Modified Becke-Johnson (mBJ) and unmodified Becke-Johnson (umBJ) potentials are also applied to obtain an enhanced band gap. Spin–orbit coupling effect (SOC) is also taken into consideration due to the heavy Bi atom. When employing the PBE+umBJ potential, BiOF exhibits the most enhanced band gap energy, with a direct band gap energy of 3.72 eV. Moreover, optical properties such as dielectric functions, absorption coefficients, and optical conductivities are also calculated for photon energies up to ̴̴ 14 eV. In comparison to other available theoretical and experimental findings, the calculated results are in good agreement.

Insights into the optoelectronic and thermoelectric properties of defect chalcopyrites XAl2Se4 (X = Zn, Cd, and Hg): A density functional theory approach

In the current study, we employed the full-potential linearized augmented plane wave plus local orbitals (FP-LAPW + lo) approach within the density functional theory (DFT) to investigate the physical properties of Defect Chalcopyrites XAl2Se4 (X = Zn, Cd, and Hg). Calculations yield precise structural and electronic parameters in good agreement with experimental data, revealing all three compounds as direct wide-bandgap semiconductors. The modified Becke-Johan potential (TB-mBJ) method accurately estimates energy gaps, which increase with decreasing lattice constants. The calculated values are 3.34 eV, 3.12 eV, and 2.30 eV for ZnAl2Se4, CdAl2Se4, and HgAl2Se4, respectively. The optical properties, including dielectric function and absorption coefficient, indicate potential applications in visible and ultraviolet optoelectronic devices. The high anisotropy of these materials further enhances their suitability for a range of linear and nonlinear optical applications. Moreover, ZnAl2Se4 exhibits the highest Seebeck coefficient at room temperature. The positive Seebeck coefficient confirmed the p-type behavior of the studied compounds. The highest observed power factor demonstrates optimal thermoelectric performance for these materials. High electrical conductivity values suggest their suitability as effective electrical conductors, especially at elevated temperatures. This study encourages further research into defect chalcopyrites for applications in optoelectronics and thermoelectric energy conversion.

Assessing the viability of hydrogen-based perovskites for optoelectronic and thermoelectric applications via first principle modeling.

In this study, we delve into the physical characteristics of six hydride perovskites of ABH3-type materials (CsCaH3, CsSrH3, KMgH3, LiBaH3, NaBeH3, and RbCaH3). Our investigation primarily focuses on assessing their structural stability by determining the enthalpy of formation and examining the dispersion of phonons. Using band structure calculations, we discern the characteristics of semiconductors, observing a direct bandgap in all four perovskites except NaBeH3 and KMgH3, which exhibit indirect gaps. Among these, NaBeH3 possesses the narrowest gap at 1.91 eV, while the widest gap is observed in the perovskite RbCaH3, measuring 4.56 eV. Furthermore, we conduct a thorough analysis of their optical properties, including parameters such as the real and imaginary dielectric function, absorption coefficient, and refractive index within an energy range of 0 to 14 eV. The results of our study are highly encouraging, suggesting that these materials hold significant promise for utilization in photovoltaic cells. This is primarily attributed to their remarkable ability to absorb light across both the ultraviolet (UV) and visible spectra. Additionally, we conducted an assessment of the thermoelectric properties of the six perovskite materials. RbMgH3 exhibits a maximum Seebeck coefficient (Smax) of 1.5 mV/K, whereas KMgH3 achieves a figure of merit reaching unity. These findings present promising opportunities for utilizing these compounds in thermoelectric devices. In this study, all self-consistent field (SCF) calculations were performed using density functional theory (DFT), employing the FP-LAPW + lo method as implemented in the Wien2k code. The Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation, the modified Becke-Johnson (mBJ) methods, and the HSE06 hybrid functional were employed to characterize the exchange-correlation interactions. Thermoelectric parameters were extracted using the BoltzTraP software.

First-principles study of electronic, mechanical, and optical properties of M3GaB2 (M = Ti, Hf) MAX phases

Integrating ceramic and metallic properties in MAX phases makes them highly desirable for diverse technological applications. In this study, through first-principles density functional theory (DFT), we investigated the physical properties of two new 312 MAX compounds, M3GaB2 (M = Ti, Hf). Chemical stability is confirmed via formation energy assessment, while mechanical stability is established by determining elastic stiffness constants. A thorough analysis of mechanical behaviors includes bulk modulus, shear modulus, Young's modulus, and hardness parameters. M3GaB2 demonstrates elastic constants and moduli closely aligned with other 312 carbides. Understanding the electronic band structure and density of states (DOS) sheds light on metallic properties, with anisotropy in electrical conductivity clarified through energy dispersion analysis. Investigation of photon interaction with titled compounds, including dielectric constants (real and imaginary parts), refractive index, absorption coefficient, photoconductivity, reflectivity, and energy loss function, has been carried out. The potential of M3GaB2 borides as a coating to reduce solar is evaluated based on the reflectivity spectra. These findings deepen our understanding of material properties and suggest diverse applications for M3GaB2 in various technological domains.

Dielectric properties of tidal volume changes in rabbit lung tissue in the 100 MHz~1 GHz band

This paper investigates the variation of lung tissue dielectric properties with tidal volume under in vivo conditions to provide reliable and valid a priori information for techniques such as microwave imaging. In this study, the dielectric properties of the lung tissue of 30 rabbits were measured in vivo using the open-end coaxial probe method in the frequency band of 100 MHz to 1 GHz, and 6 different sets of tidal volumes (30, 40, 50, 60, 70, 80 mL) were set up to study the trends of the dielectric properties, and the data at 2 specific frequency points (433 and 915 MHz) were analyzed statistically. It was found that the dielectric coefficient and conductivity of lung tissue tended to decrease with increasing tidal volume in the frequency range of 100 MHz to 1 GHz, and the differences in the dielectric properties of lung tissue for the 6 groups of tidal volumes at 2 specific frequency points were statistically significant. This paper showed that the dielectric properties of lung tissue tend to vary non-linearly with increasing tidal volume. Based on this, more accurate biological tissue parameters can be provided for bioelectromagnetic imaging techniques such as microwave imaging, which could provide a scientific basis and experimental data support for the improvement of diagnostic methods and equipment for lung diseases.

Photocurrent interference spectroscopy of solids and characterization of semiconductor solar-cell materials

Photocurrent measurements are widely used to study the intrinsic optoelectronic properties of semiconductors, such as photocarrier generation efficiency and carrier mobility, as well as evaluate the performance of optoelectronic devices, such as solar cells and photodetectors. Interferometric spectroscopy precisely measures optical properties and gathers optical spectra information on semiconductors. Consequently, photocurrent-based interferometric measurements, with high signal-to-noise ratios, high resolution, and broad frequency bandwidths, can probe the energy distributions of low-density defects and impurities and investigate charge transport in materials and devices. Here, we demonstrate that photocurrent interference spectroscopy reveals the intrinsic properties of solar-cell materials: bulk crystals of GaAs and halide perovskite, and thin films of halide perovskite and quantum dot. We show that homodyne interference spectroscopy of photocurrent can monitor low-density localized states in semiconductors and that it can be used in combination with other spectroscopy techniques, such as photoluminescence measurements, to provide a deep understanding of photocurrent generation processes. Furthermore, we show that heterodyne interference spectroscopy of photocurrent can be used to investigate the frequency dependence of material parameters, such as the dielectric constant, absorption coefficient, and reflectance. As an application, we used interference spectroscopy of photocurrent to show the impact of multiexcitons on the photoabsorption and photocarrier generation processes in quantum dot solar cells. Finally, we used it to reveal the distinctive spectral characteristics at the band edge of a halide perovskite, which is considered to be an exceptional solar-cell material with high energy conversion efficiency.

The investigation of piezoelectric features of lead-free barium titanate ceramic materials at different initial temperatures in the tetragonal phase using molecular dynamics simulation

This study used molecular dynamics simulation to investigate how temperature changes the piezoelectric properties of crystal barium titanate in its tetragonal form. Consistent with the results, the oxygen diffusion coefficient in the simulated sample increased to 0.35 Å2/ns (expansion mode) and 0.56 Å2/ns (contraction mode) by increasing the temperature from 300 to 400 K. Moreover, the piezoelectric coefficient of samples decreased from 267.22 to 162.56 in an expansion mode and from 189.96 to 145.21 in a contraction mode by increasing temperature. On the other hand, increasing the temperature decreased saturation polarization (from 0.372 to 0.290 C/m2), coercivity field (from 0.259 to 0.155 MV/m), and residual polarization (from 0.154 to 0.084). This decrease may be due to approaching the critical temperature and changing the structure from tetragonal to cubic. Finally, the results show that the dielectric coefficients were found by raising the temperatures to 400 K (expansion mode) and getting 73, 70, 68, and 64. For the contraction mode, they were 70, 66, 55, and 63.

First-principles predictions of structure, half-metallic antiferromagnetism, optoelectronic, and elastic properties of double perovskites A2TaNiO6 (A = Ca, Sr, and Ba) for energy harvesting

In this article, the electronic, half-metallic antiferromagnetism, and optical characteristics of A2TaNiO6 (A = Ca, Sr, and Ba) double perovskites have been investigated by using WIEN2k code with the GGA + PBEsol approximation. The cubic phase structures were optimized with minimum ground state energy. The electronic attributes showed a semiconductor nature for spin-up channels and a metallic nature for spin-down channels, indicating half-metallicity. Magnetic properties have demonstrated the magnetic moments and antiferromagnetic nature of the studied perovskites. The optical response was assessed by examining dielectric function, absorption coefficient, reflectivity, and energy loss function. Higher values of these parameters in the energy range of 2–4 eV suggest their potential for optoelectronics. Mechanical properties have been also investigated which demonstrated that these compounds have outstanding mechanical stability, anisotropy, mechanical strength, and ductility. The collective results reveal the importance of the analyzed compounds as promising candidates for spintronics, photovoltaics in space, UV-photodetectors, and other UV-based optoelectronic applications.