Band Gap Research Articles

Photoluminescence study of optical transitions in spinel zinc gallium oxide thin films

Spinel ZnGa2O4 is an ultra-wide bandgap material that can have a great potential for deep ultraviolet (UV) photonics and other applications. In this work, zinc gallium oxide (ZnGaO) samples with Zn composition ranging from 0.0 to 48.0 at% were grown in a plasma-assisted molecular beam epitaxy system. The change of crystal structure from beta to spinel was determined using reciprocal space mapping in x-ray diffraction. When Zn composition is at 0.0, 0.9, 3.4, and above 7.3 at%, the crystal structure exhibits beta phase, mixture phase, weak spinel phase, and strong spinel phase, respectively. Comprehensive photoluminescence (PL) of the samples were carried out using an ArF laser excitation, and PL peak deconvolution was performed to understand the optical transitions and energy levels within the forbidden gap. For spinel ZnGaO samples, five deconvoluted peaks were observed, revealing the energy levels of three oxygen vacancies, self-trapped holes binding energy, and acceptor levels.

"Two-in-One" DPP Building Blocks for Ambipolar Conjugated Polymers in Flexible Transistors.

Advancements in conjugated donor-acceptor (D-A) polymers with superior semiconducting performance and reliability are pivotal to the evolution of flexible electronics. However, the development of electron-accepting building blocks has lagged far behind that of electron-donating ones, hindering the progression of ambipolar and n-type semiconductor polymers-especially ambipolar types-and thereby limiting the construction of logic circuits and p-n heterojunctions. In this study, we introduce a new electron-accepting building block, 2Ar'Ar2DPP, meticulously engineered for semiconducting polymers tailored to flexible electronics applications. Synthesized through the modification of conventional diketopyrrolopyrrole (DPP), 2Ar'Ar2DPP─including 2TPh2DPP and 3T2DPP─incorporates structural innovations, merging a single DPP unit with two aromatic groups into a configuration featuring two DPP units and three aromatic groups. This modification enhances the electron-accepting ability and modulates intra- and intermolecular D-A interactions. 2TPh2DPP and 3T2DPP were investigated to explore their structure-property relationships. Specifically, 3T2DPP demonstrates improved backbone planarity, extended π-conjugation, and more efficient intramolecular D-A interactions. These features result in significantly lower LUMO levels and narrower band gaps compared to those of conventionally utilized thiophene-flanked DPP and even its dimer. Moreover, the change in the molecular structural symmetry of 3T2DPP induces a relatively large dipole moment, thereby enhancing intermolecular interactions. Consequently, polymers derived from 2Ar'Ar2DPP exhibit ambipolar semiconducting performance in flexible organic field-effect transistors, achieving hole and electron mobilities of up to 6.0 and 2.1 cm2 V-1 s-1, respectively, with good bending resistance. These preliminary results indicate that 2Ar'Ar2DPP holds significant promise for the future design of conjugated materials for flexible electronics.

Microhole Structure in Flexible Semitransparent Perovskite Solar Cells Using Nickel Mesh as the Framework and Electrode.

Semitransparent perovskite solar cells can provide auxiliary power in applications such as power-generating windows and smart car windows. However, in conventional planar-structured devices, both the power conversion efficiency (PCE) and the average visible light transmittance (AVT) of the devices are restricted by the band gap or thickness of the perovskite absorption layer, which hinders the development and application of semitransparent perovskite solar cells. In this work, we construct a new type of semitransparent perovskite solar cell with a three-dimensional (3D) mesh structure using nickel mesh as a framework and bottom electrode. The AVT of the device is controlled by a nickel mesh. When narrow band gap perovskite materials were deposited, the PCE of the device was 4.48%, the average visible light transmittance was 16.5%, the color rendering index was 98.35, and the bifacial coefficient reached 79%. Additionally, due to the flexible nature of the nickel mesh, the device exhibited excellent mechanical stability, maintaining 90% of its initial PCE after 1000 bending cycles at R = 10 mm. This three-dimensional mesh structure provides a new idea for realizing the transmittance of semitransparent flexible perovskite solar cells with high efficiency and high transmittance. It is expected to promote their wide application in fields such as building-integrated photovoltaics.

Optimization of amorphous silicon solar cells through photonic crystals for enhanced optical properties

Amorphous silicon solar cells have emerged as a promising technology for harnessing solar energy due to their cost-effectiveness and flexibility. However, their efficiency is constrained by low sunlight absorption resulting from the material’s indirect band gap and intrinsic properties of amorphous silicon. This study employs theoretical modeling to investigate the impact of incorporating one-dimensional ternary photonic crystals (1D-Ternary-PCs) as anti-reflection coatings (ARCs) and one-dimensional binary PCs as back reflectors to enhance the optical properties of amorphous silicon (a-Si) solar cells. The investigation utilizes the COMSOL Multiphysics program, based on the finite element method (FEM), to simulate and analyze the optical characteristics of PC-enhanced a-Si solar cells. The modeling involves designing and optimizing ternary PC structures, followed by numerical simulations to assess their anti-reflection performance. Additionally, designing one-dimensional binary PCs optimized to create a photonic band gap within the transmitted spectrum to act as a back reflector. The study systematically examines the impact of various parameters such as layer thickness, refractive indices, and incident angles on the optical properties of PC-enhanced a-Si solar cells, offering insights into the potential of one-dimensional PCs as effective back reflectors and ARCs for enhancing light absorbance and overall efficiency.

High-Performance Photoresponse and Nonvolatile Photomemory Effect in a Partially Gated MoS2/α-In2Se3 Heterojunction Photodetector.

2D ferroelectric materials exhibit exceptional properties such as atomically thin layers, strong ferroelectric polarization, high carrier mobility, and suitable band gaps, making them highly promising for electronics, optoelectronics, ferroelectronics, and nonvolatile memory applications. In this study, we present a partially gated MoS2/α-In2Se3 heterojunction photodetector that allows the manipulation of ferroelectric polarization in α-In2Se3 by both gate and drain voltages. The device shows excellent photoresponse performance and a nonvolatile photomemory effect. It achieves a maximum photoresponsivity of ∼698 A/W at 405 nm, ∼1210 A/W at 473 nm, ∼1076 A/W at 515 nm, and ∼1306 A/W at 638 nm. By enhancing the ferroelectric polarization of α-In2Se3, the photoresponsivity, external quantum efficiency, and detectivity are greatly improved. The photomemory effect has an extremely long retention time exceeding 4000 s with an expected information retention rate of over 95% after 10 years. The device performance is a result of the combined effects of vertical-electric-field-controlled ferroelectric polarization, horizontal-electric-field-controlled ferroelectric polarization, and light-induced depolarization. The proposed partially gated MoS2/α-In2Se3 heterostructure provides a new perspective for designing 2D ferroelectric devices with significant potential for optoelectronics and nonvolatile memory applications.

Mechanism Decoding of an S-Scheme ZnIn2S4/H2WO4 Heterojunction with Favorable Surface Electronic Potential for Enhanced and Anti-Corrosion Photocatalytic Hydrogen Evolution.

The rational construction of heterojunction interfaces plays a critical role in enhancing the carrier separation efficiency for photocatalytic hydrogen evolution. In this study, a ZnIn2S4/H2WO4 S-scheme heterojunction was successfully synthesized via a self-assembly strategy. Compared with conventional WO3, the H2WO4 component exhibits a lower work function, which significantly promotes surface electron overflow and establishes an optimized S-scheme charge transfer pathway. Structural characterization reveals that the intimate integration of H2WO4 nanosheets within ZnIn2S4 nanoflowers provides enhanced interfacial contact, thereby facilitating efficient charge separation and migration. As a result, the optimized ZnIn2S4/H2WO4 composite demonstrates a hydrogen evolution rate of 138 mmol/g/h, achieving a 4.7-fold enhancement over pristine ZnIn2S4 and a 1.9-fold improvement compared to the ZnIn2S4/WO3. This work highlights the dual requirements for oxidation photocatalysts in S-scheme systems: precise band gap alignment and favorable surface electronic properties, both essential for enabling efficient electron overflow and ensuring effective S-scheme charge migration channels.

Sustainable Nanoparticle Synthesis Using Tinospora cordifolia (Giloy) Leaves Extracts: Evaluation of Antimicrobial Efficacy Against MultiDrug Resistant Bacteria and Optical Features

Sustainable synthesis, also known as environmentally benign synthesis, of nanoparticles, presents an energy and resource-efficient approach for the development of nanoparticles to advanced materials with considerable biomedical potential. This study focuses on the synthesis of zinc oxide (ZnO) nanoparticles using Tinospora cordifolia (Giloy) leaves, aqueous extract as a natural strengthening and stabilizing and natural reducing agent. The bioactive compounds present in the leaves extract facilitated the reduction of zinc ions (Zn2+) to ZnO nanoparticles under optimized reaction conditions. For the characterization of nanoparticles, analytical tools were used like UV-Vis spectroscopy and X-ray diffraction (XRD) to determine the size of nanoparticles, their morphology, and crystalline structure. Green-synthesized ZnO nanoparticle's optical properties and their energy band gap were evaluated, which revealed an energy band gap of approximately 3.12 eV, which suggests their efficiency for photocatalytic and biomedical applications. The antimicrobial potential of the green-synthesized ZnO nanoparticles was assessed against a pathogen associated with waterborne infections which is Aeromonas hydrophila, showcasing multidrug-resistant (MDR) activity. The nanoparticles exhibited significant biocidal activity, with a zone of inhibition that is directly correlated to the size of nanoparticles and their concentration. The effectiveness of antimicrobial activity is attributed to the unique physicochemical properties of the ZnO nanoparticles, including a high surface area and size-dependent reactivity, which increases their interaction with bacterial cell membranes. This study brings to light the potential of Tinospora cordifolia-mediated green synthesis of ZnO which is a renewable and competent method for producing biofunctional ZnO nanoparticles. The encouraging antimicrobial activity, coupled with their tunable optical properties, positions these nanoparticles as valuable agents in combating multidrug-resistant bacteria, with further applications in nanomedicine, biosensing, and environmental remediation technologies. Received: 20 December 2024 | Revised: 26 March 2025 | Accepted: 16 April 2025 Conflicts of Interest The authors declare that they have no conflicts of interest to this work. Data Availability Statement The data sharing is not applicable to this article as no new data were created or analyzed in this study. Author Contribution Statement Jyoti Jaglan: Conceptualization, Methodology, Writing – review & editing, Supervision. Anshu Jaglan: Methodology, Validation, Investigation, Writing – review & editing, Project administration. Bajinder Singh: Formal analysis, Resources. Harsh Jaglan: Software, Formal analysis, Resources, Data curation, Visualization. Preeti Jaglan: Validation, Investigation. Savita Jaglan: Investigation, Writing – original draft. Monika Brala: Conceptualization, Writing – original draft, Visualization, Project administration.

Cobalt, nickel and zinc spinel ferrites with high transmittance and UV-blocking for advanced optical applications

This study successfully synthesized and characterized CoFe2O4, NiFe2O4, and ZnFe2O4 ferrite nanoparticles. The results showed that CoFe2O4 and NiFe2O4 exhibited ferrimagnetic behavior, while ZnFe2O4 demonstrated antiferromagnetic properties. These magnetic characteristics influence the material’s response to electromagnetic radiation, such as visible and infrared light. Optical studies revealed that CoFe2O4 had the highest radiation absorption, while ZnFe2O4 showed superior reflection and transmission. The ferrites’ band gap energies, ranging from 3.3 to 3.6 eV, played a key role in their optical properties, with higher energy absorption and lower energy reflection. The refractive index varied with photon energy, reaching its peak at lower energy levels due to oxygen vacancies. Additionally, the optical conductivity increased with higher photon energy, peaking at 4.3 eV. These findings suggest promising applications in light transmission and sensing, with ferrites offering versatile optical properties that can be tailored for various uses.

Tunable properties of silver (Ag) substituted BaFe2O4 nanoparticles for photovoltaic (PV) applications

In this work, Ba1-xAgxFe2O4 (x = 0.0, 0.2, 0.3, 0.5) nanoparticles have been prepared using the sol–gel auto-combustion method providing the pioneering investigation of substitution of silver into barium ferrite, that is often associated with magnetic applications. A broad inspection has been performed on structural, magneto-electric, dielectric, and optical properties uncovering potential of Ag incorporated barium ferrite nano particles using X-ray diffraction, Vibrating sample magnetometer, Multiferroic system, Impedance Analyzer, UV visible diffuse reflectance spectroscopy, Fluorescence spectrophotometer and Photoluminescence (PL) system. The chemical bonding and functional groups of all samples were explored by Fourier transform infrared spectrometer as well as with RAMAN spectroscopy. The slight turn in orthorhombic structure from (Pnma 62) to (Bb21m 36) was detected from pure BaFe2O4 particles to Ag concentrated samples and also illustrated in 3D visualization. The formation of spherical nanoparticles (46-32 nm) with designed composition (Ba0.8Ag0.2Fe2O4, Ba0.7Ag0.3Fe2O4, Ba0.5Ag0.5Fe2O4) which was confirmed by Scanning electron microscopy and Energy dispersive x-ray spectroscopy separately. The maximum magnetization value of 22.3 emu/g was revealed by the Ba0.5Ag0.5Fe2O4 sample. The lowest energy band gap value of 1.5–1.8 eV was achieved by pristine and Ba0.7Ag0.3Fe2O4 making it eligible to operate within the ideal region of solar cell efficiency with reduced recombination losses. The PL emission intensity was also observed in the visible spectrum at 573–576 nm for Ag concentrated samples suggesting that material can efficiently absorb and release light in the solar spectrum’s most useful region. Significant leakage current was indicated by the PE loop with high conductivity, indicating that the material has reduced resistance and enhanced charge transport. Simulating solar illumination was used to evaluate the photovoltaic performance of nanoparticles, producing response curves for photocurrent and dark current revealing the improved photo current with Ag infusion. The valuable results of Ag-infused barium ferrites for dielectric, optical, and photovoltaic capabilities offered a fresh concept for using magnetic nanoparticles modified by silver as an encouraging development in the PV applications.Graphical

Optimizing CdS thin films as optical windows in solar cells: A comparative study of cryogenic and classical techniques

In this study, CdS thin films were produced in a quasi-closed volume using two different techniques (classical and cryogenic thermal evaporation techniques) between the 100–573 K substrate temperature, and their characteristic properties (structural, electrical, and optical properties) were investigated. While CdS thin films were produced at 373 K, 473 K, and 573 K substrate temperatures in the classical technique (hot), they were produced at 100–300 K substrate temperature range with 50 K steps in the cryogenic technique (cold). The X-Ray Diffraction (XRD) analysis showed that the CdS thin films grew in a hexagonal structure in the (002) plane at all substrate temperatures. According to the field emission scanning electron microscope (FESEM) images, the thin films produced at 200 K substrate temperature consisted of equally sized spherical grains. This situation shows that the soliton growth mechanism occurs at a substrate temperature of 200 K during the film production process with the cryogenic technique. Due to the characteristic properties of the soliton waves occurring on the substrate surface in the soliton growth mechanism (mass transport), the films grow in a tight-packed form. Therefore, the produced films consist of clusters of equal size, providing a homogeneous surface and a uniform thickness. In addition, Atomic Force Microscope (AFM) and optical analyses showed that the CdS thin film produced at 200 K substrate temperature had the smallest average surface roughness value (Ra) and the highest optical transmittance value. It was found that the energy band gap (2.37–2.47 eV) and resistivity (1.25 × 103–5.39 × 103 Ω-cm) values ​​of CdS thin films increased with decreasing substrate temperature. The carrier density increased with decreasing substrate temperature (3.91 × 1017–1.73 × 1016 cm−3). Energy Dispersive Spectroscopy (EDS) analysis showed that the films grew stoichiometrically at substrate temperatures of 473 K and 200 K. The results brought out that in case of using of the produced CdS thin films at a substrate temperature of 200 K by the new cryogenic technique as an optical window layer could provide significant increases in efficiency in solar cells. In addition, ideal substrate temperature values ​​for CdS thin films that can be used in photodevice production were determined for both techniques.

Modeling the functionalized genistein-hyoscyamine derivatives

Due to the significant rise in demand for functional foods and health-conscious alternatives, natural extracts present a promising avenue for exploration and application within the food processing sector. For many individuals suffering from monosymptomatic nocturnal enuresis (MNE) and its accompanying complications, supplying the market with a functional food that aids accelerating resolving this problem will be a very valuable addition. Thus, in this study we aimed to validate and functionalize modeled composite of Genistein-Hyoscyamine as to further employ the best match in food processing sector as a novel food-additive for functional-foods serving enuretic patients. In attempts to model the most chemically favorable and experimentally achievable composite structures we thoroughly studied the parent molecules employing various DFT descriptors, selected electronic and thermodynamic parameters that help foresee and assess the structures’ behavior and stability in various conditions that are common during food processing. Afterwards, composites were primarily assessed through selected ADME parameters in regard to their suitability for ingestion, water solubility, GI absorption, bioavailability score, and synthetic accessibility. Based on the screening of modeled structures, composites number 02 and 04 were found to possess the most favorable structures and characteristics where composite number 02 has shown relatively higher band gap energy and dipole moment as well as slightly more heat capacity; while composite number 04 has shown higher lipophilicity as well as lower TPSA value, less enthalpy, free energy, and entropy, suggesting more stability and bioavailability. Highlighting their suitability for being introduced to food matrices as food-additives in the form of composite bioactive materials.

Performance analysis of Thue Morse acoustic resonators for noise reduction

This article explores acoustic band gap in the Thue-Morse phononic crystal structures for application in acoustic filtering. By using the unique nature of Thue-Morse sequences, we systematically analyze transmission spectra over many generations of structures using the transfer matrix and finite element methods. The proposed generalized Thue-Morse is constructed by alternating blocks based on two resonator sequences. The first sequence consists of parallel open resonators while the second block has an open resonator. The results show that acoustic band gaps can be widened and fragmented by adjusting resonator coupling strength and structural complexity. Higher-order resonances and localized modes enable the formation of sub-gaps in the frequency-selective response. These findings highlight the potential of Thue-Morse phononic crystals for precise acoustic filtering and wave manipulation in advanced material applications.

Stability of ferromagnetism in diluted magnetic Sr1−xCrxX (X = S, Se and Te) semiconductor doped by Cr under Hubbard correction and strain effect

Abstract This study focuses on the electronic, magnetic, and elastic features of strontium chalcogenides SrX (X = S, Se, Te) doped with chromium (Cr) using ab-initio calculations, in the presence and absence of the Hubbard correction (U) and strain effect. The results show that adding Cr induces a half-metallic behavior and a stable ferromagnetic phase, with spin polarisation reaching 100% in the absolute majority of cases. The stability of this phase is confirmed by negative formation energies and high Curie temperatures, above room temperature, achieving its maximum values of 464K, 475 K, and 570 K for SrS, SrSe, and SrTe, respectively, at 24% of the chromium portion. The effect of applied strains (2% and 4%) reveals a modulation of the electronic properties, visualized by the shift in density of state (DOS) and the decrease of the band gap. A strengthening of the magnetic interactions while retaining the half-metallic character is also observed under strain. Since Cr-doped SrS has large elastic moduli and remarkable mechanical properties, it is a perfect choice for strong spintronic devices and spin filters that need mechanical stability. Its ability to blend mechanical strength and ductility makes Cr-doped SrSe a promising material for magnetic tunnel junctions (MTJs) in MRAM. For flexible spintronic devices, including SpinFETs, Cr-doped SrTe is an excellent choice due to its enhanced ductility (increased B / G ratio) and maximal deformability. These results highlight the potential of Cr-doped SrX compounds to improve device performance, efficiency, and functionality by relying on the interaction of ferromagnetism and elastic property tuning. The combination of all our findings makes our compound promising for spintronic applications.

Dynamic Charge Transport Behavior of Double-layer Thin Film Materials Under Electron Beam Irradiation

Abstract Spacecraft dielectrics in the complex space environment often suffer charging and discharging, causing on-orbit anomalies and failures. Studying charge transport in the dielectric during a spacecraft's charging process is crucial. It helps take measures like surface coating to regulate the surface potential and reduce electrostatic discharges. A double-layer material electron self-consistent transport model, which can simulate the dynamic charge transport behavior of coated spacecraft dielectrics under electron beam irradiation, is developed and used to numerically simulate coated polyimide. It reveals the spatial-temporal distributions of microscopic quantities (charge density, electric field), and temporal evolutions of macroscopic quantities (surface potential, secondary electron yield). Then, the effects of intrinsic properties including electron affinity, band gap, mass density, relative permittivity, and trap density of coating materials on the charging process of spacecraft dielectrics are analyzed, including above microscopic and macroscopic quantities. It is found that decreases in mass density and increases in electron affinity, band gap, and trap density decrease the absolute value of the steady-state surface potential, while the relative permittivity is shown to exert only limited. Obtained trends guide coating material selection for surface charging mitigation. Four coated polyimides' (PI) steady-state potentials are compared, and the Diamond-like Carbon(DLC) coating with the lowest absolute value of steady-state surface potential is selected to further analyzed for the effect of coating thickness. It is found that the absolute value of the steady-state potential decreases with the increase of the coating thickness, but the effects gradually saturates as the thickness increases. Finally, DLC with a thickness of 200nm is chosen as the optimal PI coating material, which significantly prevents the charging level from becoming too high while avoiding the negative effects that may be brought about by over-coating, and achieves the purpose of mitigating the electrostatic discharge and improving the stable operation of the spacecraft.

Design of a novel visible light bandstop photonic crystal filter based on mesoporous SiO2 thin films

Abstract Currently, within the spectral ranges of visible light, ultraviolet radiation, and high-energy x-ray photons, the predominant filtering technology employed is the photonic crystal (PC) passband filter. Nevertheless, these filters exhibit notable limitations, such as a relatively restricted filtering frequency range and intricate fabrication processes. In response to the aforementioned challenges, this paper introduced for the first time the concept of a structurally simple and wideband-stopband filter based on mesoporous SiO2 thin films, thereby offering a novel solution for relevant domains. The transfer matrix method was used to analyze the impact of different filling ratios and lattice constants on the photonic band gap (PBG) properties of mesoporous SiO2 thin films. The results showed that, under the optimal filling ratio (r/a = 0.06), narrow PBGs and high transmission could be achieved in the violet (437.54 nm), green (510.46 nm), yellow (583.55 nm), and red (656.35 nm) light bands by adjusting the lattice constant. By extending the range of the horizontal axis for analysis, it was observed that the stopband range of the designed filter had substantially broadened, covering wavelengths above 227.9 nm, 264.8 nm, 303.4 nm, and 340.3 nm, respectively. Consequently, a novel filter with wide bandwidth, narrow bandgap, high reflectivity, and a simplified fabrication process was successfully developed. Additionally, in the X-Z and Y-Z planes, the position and properties of the PBG remained largely unchanged when the incident angle is less than 11.5°. This study not only expands the theoretical research scope of PC materials but also opens new possibilities for their practical applications.

Synthesis and Photocatalytic Properties of Manganese-Substituted Layered Perovskite-like Titanates A′2La2MnxTi3−xO10 (A′ = Na, H)

The search for effective and reliable methods of photosensitization of oxide-based semiconductor materials is of great significance for their use in photocatalytic reactions of hydrogen production and environmental remediation under natural sunlight. The present study is focused on partial substitution of titanium with manganese in the structure of layered perovskite-like titanate Na2La2Ti3O10, which was employed to yield a series of photocatalytically active materials, Na2La2MnxTi3−xO10 (x = 0.002–1.0), as well as their protonated forms H2La2MnxTi3−xO10 and nanosheets. It was established that the manganese cations Mn4+ are embedded in the middle sublayer of oxygen octahedra in the perovskite slabs La2MnxTi3−xO102− and that the maximum achievable manganese content x in the products is ≈0.9. The partial cationic substitution in the perovskite sublattice led to a pronounced contraction of the optical band gap from 3.20 to 1.35 eV (depending on x) and, therefore, allowed the corresponding photocatalysts to utilize not only ultraviolet, but also visible and near-infrared light with wavelengths up to ≈920 nm. The materials obtained were tested as photocatalysts of hydrogen evolution from aqueous methanol, and the greatest activity in this reaction was demonstrated by the samples with low manganese contents (x = 0.002–0.01). However, the materials with greater substitution degrees may be of high interest for use in other photocatalytic processes and, especially, in thermophotocatalysis due to their improved ability to absorb the near-infrared part of solar radiation.

Development of two semiconducting supramolecular metallogels of Cd(II)- and Hg(II)-ions from 5-aminoisophthalic acid gelator for high-performance Schottky diodes and advanced microelectronic applications

Two novel metallogels, designated as Cd-AIA and Hg-AIA, were synthesized at ambient temperature utilizing 5-aminoisophthalic acid (AIA) as the gelator, along with cadmium(II) acetate and mercury(II) acetate in N,N-dimethylformamide. Rheological tests validated the mechanical robustness of the Cd(II)- and Hg(II)-based metallogels under various conditions. Characterization techniques, including EDX mapping and FESEM imaging, were employed to explore the chemical composition and microstructural details of these gels. The formation mechanisms of the metallogels were elucidated through FT-IR and Raman spectroscopy. PXRD was used to confirm the crystalline nature of the synthesized gels. TGA of Cd-AIA and Hg-AIA metallogels analyse the thermal stability of the metallogels upto 250 ºC. The optical band gaps were determined from the absorption spectra, indicating a strong semiconducting behavior. The semiconducting properties were further confirmed by electronic device characterization and charge carrier mobility assessments. Notably, the electron mobility observed in these metallogels is exceptionally high, potentially setting a new benchmark compared to previously reported values. A significant difference in conductivity was found between the two gels, with the Hg-AIA metallogel displaying superior semiconducting properties. Moreover, when tested under the same device configuration, the Hg-AIA diode exhibited better switching performance, a higher on–off ratio, and lower series resistance than the Cd-AIA diode. The I-V characteristics revealed a broad non-linear behavior, with the Cd-AIA diode showing greater non-linearity, likely due to its higher series resistance compared to the Hg-AIA diode. Graphical

Engineering defect clustering in diamond-based materials for technological applications via quantum mechanical descriptors

Dopant-dopant and dopant-vacancy complexes in diamond can be exploited for the development of quantum computers, single-photon emitters, high-precision magnetic field sensing, and nanophotonic devices. While some dopant-vacancy complexes such as nitrogen- and silicon-vacancy centers are well studied, studies of other dopant and/or vacancy clusters are focused mainly on defect detection, with minimal investigation into their electronic features or how to tune their electronic and optical properties for specific applications. To this aim, we perform a thorough analysis of the coupled structural and electronic features of different dopant-dopant and dopant-vacancy cluster defects in diamond by means of first-principles calculations. We find that doping with p-type (n-type) dopant does not always lead to the creation of p-type (n-type) diamond structures, depending on the kind of cluster defect. We also identify the quantum mechanical descriptors that are most suitable to tune the electronic band gap about the Fermi level for each defect type. Finally, we propose how to choose suitable dopant atomic types, concentrations, and geometric environments to fabricate diamond-based materials for several technological applications such as electrodes, transparent conductive materials, intermediate-band photovoltaics, and multicolor emitters, among others. Published by the American Physical Society 2025

Ab Initio Study of the Electronic, Thermodynamic, Thermoelectric, and Optical Properties of HfSeS in the (100), (110), and (111) Crystallographic Directions

AbstractIn this article, the results of theoretical calculations are presented on the structural, electronic, thermodynamic, thermoelectric, and optical properties of the compound HfSeS grown in the (100), (110), and (111) crystallographic directions. These properties are studied with the aid of calculations based on density functional theory, using the Generalized Gradient Approximation (GGA) approximation and spin‐orbit coupling (SOC). These electronic calculations reveal that HfSeS exhibits an indirect band gap of the M‐Γ type for all directions, with strong alignment between the results obtained employing the GGA and SOC approaches. For the study of optical properties, pressure is applied to better understand the properties of the material under various conditions. The thermodynamic properties of HfSeS are calculated, including heat capacities, thermal expansion, Debye temperature, and entropy, under elevated pressures and temperatures. These calculations are performed using the quasi‐harmonic Debye model integrated into the Gibbs2 code, and the results are analyzed in detail to better understand the thermodynamic properties of the material under various conditions. Finally, the thermoelectric properties such as the Seebeck coefficient and the electronic thermal conductivity are analyzed.

Vacancy-Ordered Hybrid Two-Dimensional Bi(III) Iodides with (100)-Oriented Dion-Jacobson Perovskite-Related Structures.

Two-dimensional (2D) hybrid iodide perovskites, (R-NH3)2MI4 and (H3N-R-NH3)MI4 (R = alkyl group; M = divalent metal ion), are promising materials for optoelectronics. Traditionally, these compounds contain Pb2+ and Sn2+ ions in the M-site; however, concerns over the toxicity of Pb2+ and the instability of Sn2+ ions have driven interest in Bi3+ halide-based alternatives. This study reports two Dion-Jacobson type, vacancy-ordered 2D Bi-I perovskites: (H2DAC)Bi2/3□1/3I4, with vacancy in every third metal site and (H2DAP)BiBi1/2□1/2I3·(I3)1/2, with vacancy in every second metal site (H2DAC = trans-1,4-diammoniumcyclohexane, H2DAP = 1,5-diammoniumpentane, and □ = vacancy). The band gaps of (H2DAC)Bi2/3□1/3I4 and (H2DAP)Bi1/2□1/2I3·(I3)1/2 are 2.11 and 1.97 eV, respectively─both narrower than that of Pb2+-based analogue (H2DAC)PbI4 (2.36 eV). These compounds show a positive photoresponse under light exposure, with the highest response observed in the case of (H2DAP)Bi1/2□1/2I3·(I3)1/2. This enhancement is attributed to the presence of I3- ions, which not only cross-link the perovskite layers and stabilize the H2DAP cation in its zigzag conformation but also contribute to the frontier orbitals. DFT calculations corroborate these experimental results. Overall, this study introduces an approach for synthesizing hybrid Bi(III)-I perovskites, which may be further investigated as lead-free optoelectronic materials, including in perovskite photovoltaics.