Band Gap Semiconductor Research Articles

Engineering sulfur doped flower-like BiOBrxI1-x solid solutions for strengthened photocatalytic activities

In this work, a series of S-doped BiOBrxI1-x solid solutions are fabricated via a simple and rapid solvothermal process. Various characterization techniques are used to thoroughly investigate the as-fabricated solid solutions. Interestingly, compared to BiOBrxI1-x, S-doped BiOBrxI1-x solid solutions exhibit a loose flower-like structure comprised of thinner nanosheets, which contributes to the enhanced specific surface area, as assessed by Brunauer-Emmett-Teller analysis. Furthermore, S-doped BiOBrxI1-x solid solutions reveal boosted visible-light response and rapid separation of photoinduced charge carriers, as verified by optical, photo-electrochemical, and electrochemical analysis. These lead to superior visible-light photocatalytic properties of S-doped BiOBrxI1-x solid solutions on pollutant removal, N2 fixation, and microplastic degradation. The crystal structure, morphology, and photocatalytic stability of the prepared samples are demonstrated by comparing their X-ray diffraction patterns, scanning electron microscopy images, and photocatalytic degradation as well as nitrogen reduction performance before and after six catalytic recycles. Furthermore, based on Density Functional Theory simulations, significant modifications in the band gap of BiOBrxI1-x solid solutions occur as iodine content increases while sulfur doping further refines the electronic features, which aligns with the results of Tauc plots. This research proves that S doping is a viable strategy for modulating the electronic structures of BiOBrxI1-x solid solutions for improving its photocatalytic performance, and provides a new route for optimizing the bandgaps of semiconductors via the non-metallic doping strategy.

Electronic Structure Of Cobalt Phosphates Co1-xmxpo4 Doped With Iron And Nickel Atoms

In this research, the electronic states, band structures, and bond properties of the framework compounds of CoPO4, Co1-xFexPO4, and Co1–xNixPO4 were investigated by the density functional theory calculations. The potential capabilities of these systems in the photocatalytic water splitting to produce hydrogen were analyzed. The spin-up electron densities of states for the CoPO4, Co1–xFexPO4, and Co1–xNixPO4 systems have band gaps of 2.7, 3.4, and 3.45 eV, respectively. The band of spin-down electron states has several energy gaps above the Fermi level. The density of states of electron with spin up near the Fermi level is obviously greater than that of electrons with spin down. In this case, localized states of electrons appear in the band gap of doped semiconductors due to impurity atoms. The calculated value of the energy at the lower edge of the conduction band for CoPO4 was –0.7 eV, which is more negative than the energy required for water splitting. Meanwhile, the calculated value of the energy at the upper edge of the valence band was 2.01 eV, which is more positive than the oxygen evolution energy of 1.23 eV.

Charge Carrier Density in Organic Semiconductors Modulates the Effective Capacitance: A Unified View of Electrolyte Gated Organic Transistors.

A framework for electrolyte-gated organic transistors (EGOTs) that unifies the view of interfacial capacitive coupling of electrolyte-gated organic field-effect transistors (EGOFETs) with the volumetric capacitive coupling in organic electrochemical transistors (OECTs) is proposed. The EGOT effective capacitance arises from in-series capacitances of the electrolyte/gate electrode and electrolyte/channel interfaces, and the chemical capacitance of the organic semiconductor channel whose weight with respect to the interfacial capacitance is modulated by the charge carrier density, hence by the gate voltage. The expression for chemical capacitance is derived from the DOS of the organic semiconductor, which it is assumed to exhibit exponential energy disorder in the HOMO-LUMO gap. The analytical expression of the EGOT current is assessed on experimental data and shown to accurately predict the shape of the whole transfer curve of an EGOT thus allowing to extract accurate values for the switch-on voltage and the interfacial transconductance, without assumptions on specific response regime and, in OECT, without invoking the volumetric capacitance. Interestingly, the EGOT model recovers EGOFET and OECT as limit cases and, in the latter case, explicitly represents the volumetric capacitance in terms of the energy disorder and the bandgap of the organic semiconductor.

Rhodium‐Alloyed Beta Gallium Oxide Materials: New Type Ternary Ultra‐Wide Bandgap Semiconductors

AbstractBeta gallium oxide (β‐Ga2O3) is an ultra‐wide‐bandgap semiconductor with advantages for high‐power electronics. However, the power resistance of β‐Ga2O3‐based devices is still much lower than its material limit due to its flat band dispersion at its valence band maximum (VBM) and the difficulty for p‐type doping. Here, β‐Ga2O3‐based new type ternary ultra‐wide bandgap semiconductors: β‐(RhxGa1‐x)2O3’s alloys are reported with x up to 0.5. The energy and band‐dispersion curvature of β‐Ga2O3’s VBM are significantly enhanced via Rh‐alloying. Compared to that in β‐Ga2O3, the β‐(RhxGa1‐x)2O3’s VBMs increase more than 1.35 eV. The hole mass of β‐(Rh0.25Ga0.75)2O3 is only 52.3% of that in β‐Ga2O3. The decreased hole mass is correlated with the equal Rh─O bond along the b‐axis. Thanks to the simultaneous rise of conduction band minimums, the bandgaps of β‐(RhxGa1‐x)2O3 are still much larger than that in commercial silicon carbide. Moreover, the alloys show direct bandgaps in a wide range of x, and a direct and ultra‐wide bandgap of 4.10 eV is determined in β‐(Rh0.3125Ga0.6875)2O3. Combined with the enhanced valence energy, reduced hole mass, and ultra‐wide bandgap, the β‐(RhxGa1‐x)2O3 can be candidate semiconductors for a new generation of power electronics, ultraviolet optoelectronics, and complementary metal‐oxide‐semiconductor (CMOS) technologies.

Piezoelectric-mediated two-dimensional copper-based metal–organic framework for synergistic sonodynamic and cuproptosis-driven tumor therapy

Sonodynamic therapy (SDT) is a minimally invasive therapeutic approach that utilizes sonosensitizers to catalyze substrates and generate reactive oxygen species (ROS) under ultrasound stimulation, ultimately inducing tumor cell death. Enhancing the piezoelectric properties of nanomaterials and modulating the semiconductor energy band are effective strategies to improve the catalytic efficiency of sonosensitizers. In this study, we developed a two-dimensional (2D) copper-based piezoelectric metal–organic framework (MOF) sonosensitizer, denoted as CM, through the coordination of copper and dimethylimidazole. The unique 2D MOF structure imparts CM with piezoelectric characteristics, enabling it to enhance SDT efficacy by modulating the semiconductor bandgap and carrier mobility. Upon ultrasound irradiation, CM catalyzes oxygen to undergo a cascade reaction, producing highly toxic singlet oxygen. Additionally, cupric ions in CM can be reduced by glutathione, facilitating the spontaneous catalysis of hydrogen peroxide in tumors to generate hydroxyl radicals and deplete glutathione, thereby inducing oxidative damage. Moreover, cupric ions in CM can trigger tumor cell cuproptosis, which, in combination with the generated ROS, accelerates cell death. Thus, this study establishes a MOF-based system for controllably inducing multi-pathway cancer cell death and provides a foundation for enhancing ultrasound-catalyzed tumor therapy through the optimization of piezoelectric properties.

Zeolite-decorated black TiOx quantum dots for photocatalytic degradation of organic cationic dyes under LED light irradiation

Defect engineering is a promising strategy to reduce the band gap of semiconductors, enhancing their photocatalytic activity under visible light by introducing intra-bandgap energy states. Among the materials studied, oxygen-deficient black TiOx stands out due to its potential in photocatalytic reduction and hydrogen evolution. However, the valence band edge maximum (VBM) of TiOx is not thermodynamically favorable for the direct oxidation of water to hydroxyl radicals (H2O/•OH). Although the formation of extensive oxygen vacancies is necessary to extend the light absorption of black TiOx to longer wavelengths, a high density of oxygen vacancies (Ov) significantly shortens the diffusion length of charge carriers within the TiOx, leading to increased recombination of electrons and holes (e-/h+), thereby suppressing photocatalytic activity. To overcome these limitations, confining TiOx particles to the quantum dot (QD) size range and constructing heterojunctions with a secondary phase can substantially improve charge carrier separation and photocatalytic performance. In addition to engineering the electronic structure of composite photocatalysts, the preaccumulation of pollutants and their subsequent degradation is an effective strategy. This method decreases the distance between the adsorbed pollutant and the active sites for reactive oxygen species (ROSs) generation, enhancing the efficiency of the photocatalytic degradation process. In this study, we confined TiOx particles to the quantum dot size range by constructing a heterojunction with H-Beta zeolite, which contains defect-induced energy states within its wide band gap. This type of zeolite is particularly effective in adsorbing cationic azo dyes, facilitating pre-accumulation and degradation. The synthesized catalysts were extensively characterized using HRTEM to determine the average size of the TiOx particles and photoluminescence (PL) analysis to investigate charge carrier separation. Our results demonstrated that while TiOx alone showed negligible degradation efficiency, and no •OH were detected, the QD TiOx/Z4 composite achieved complete oxidation of CV by •OH, as confirmed by TOC analysis. The photocatalytic degradation mechanism was proposed based on these experimental findings. These insights could be of significant interest to researchers exploring defective semiconductors for photocatalytic oxidation of organic pollutants in the liquid phase under visible light (LED) irradiation.

Impact of passivation on GaS nanoflakes: A study on stability, electronic, spectroscopy, and photocatalytic properties

This study uses first-principle calculations to investigate the properties of pristine and passivated gallium sulfide nanoflakes. Passivation significantly enhances stability, with fluorinated nanoflakes being the most stable and pristine nanoflakes the least stable, having formation energies of −0.058 eV/atom and −0.009 eV/atom, respectively. The pristine and passivated nanoflakes show semiconducting band gap, which lies in a visible region. Hydrogenated nanoflakes exhibit the largest band gap of 3.62 eV, making them highly suitable for photocatalysis, while fluorine and chlorine passivation result in band gaps of 3.16 eV and 3.01 eV. Scanning tunneling microscopy reveals distinct topographical features for each passivated nanoflake, affecting their electronic properties, including negative differential conductance, making it suitable for advanced switching devices and sensors. The quantum capacitance value of 815 µF/cm2 for chlorinated nanoflakes suggests that passivated nanoflakes could be beneficial for supercapacitor applications. Spectroscopic studies show that passivation changes the infrared spectrum and moves absorption spectra from the ultraviolet to the visible range. The hydrogenated nanoflakes are found ideal for water splitting, and adjusting the pH can further optimize its photocatalytic performance. These findings highlight the potential of passivated nanoflakes in photovoltaics, biomedical imaging, photocatalysis, and advanced technological devices.

Atomic Structures and Electronic Properties of Carbide Surfaces Unraveled by Scanning Tunneling Microscopy

AbstractCarbides, especially transition metal carbides (TMCs) and non‐metallic silicon carbides (SiCs), have registered wide applications in catalysis, superconductivity, semiconductor, and the like. Systematic studies have demonstrated the essential role of carbon in finetuning the atomic structures and electronic properties of carbides to improve their catalytic performance, superconducting transition temperature, and semiconductor bandgap. These advancements have positioned carbides as efficient substitutes for noble metals and crucial components in technological innovations. Scanning tunneling microscopy (STM) has emerged as a powerful technique in these studies, providing high‐resolution visualization and mapping of the surface geometric and electronic structures of these functionalized carbides. This review mainly focuses on the key aspects like the structures and properties of the aforementioned TMC and SiC surfaces unraveled by STM, aiming at understanding the fundamentals behind the state‐of‐the‐art technologies and advanced applications of the carbide‐involved functional systems. A very brief perspective on this topic is also provided at the end.

High-pressure synthesis, structure and physical properties of two quasi-one-dimensional compounds Ba9Nb2.54Te15 and Ba9Ta1.89Te15

Two quasi-one-dimensional compounds Ba9Nb2.54Te15 and Ba9Ta1.89Te15 were synthesized under high pressure and high temperature conditions and systematically characterized by structural, transport and magnetic measurements. Both the two compounds crystallize into a hexagonal structure with the space group P-6c2 (No. 188). The structure consists of trimeric face-sharing octahedral Nb/TaTe6 chains separated by a large distance (>10 Å), thus presenting a strong one-dimensional crystal structure. The transport properties suggest that both the two compounds are semiconductors with a band gap ∼ 0.15 eV for Ba9Nb2.54Te15 and ∼ 0.22 eV for Ba9Ta1.89Te15. Magnetic properties characterization indicates that Ba9Nb2.54Te15 displays no long-range-order above 2 K, but with an effective moment μeff ∼ 1.8 μB/f.u., while Ba9Ta1.89Te15 exhibits a diamagnetic behavior. Our results demonstrate that, in the sequence of Ba9V3Te15, Ba9Nb2.54Te15 and Ba9Ta1.89Te15, the occupation in the transition metal sites decreases, the semiconducting band gap increases, and the magnetism changes from ferromagnetism to diamagnetism.

Printing of 3D photonic crystals in titania with complete bandgap across the visible spectrum.

A photonic bandgap is a range of wavelengths wherein light is forbidden from entering a photonic crystal, similar to the electronic bandgap in semiconductors. Fabricating photonic crystals with a complete photonic bandgap in the visible spectrum presents at least two important challenges: achieving a material refractive index > ~2 and a three-dimensional patterning resolution better than ~280 nm (lattice constant of 400 nm). Here we show an approach to overcome such limitations using additive manufacturing, thus realizing high-quality, high-refractive index photonic crystals with size-tunable bandgaps across the visible spectrum. We develop a titanium ion-doped resin (Ti-Nano) for high-resolution printing by two-photon polymerization lithography. After printing, the structures are heat-treated in air to induce lattice shrinkage and produce titania nanostructures. We attain three-dimensional photonic crystals with patterning resolution as high as 180 nm and refractive index of 2.4-2.6. Optical characterization reveals ~100% reflectance within the photonic crystal bandgap in the visible range. Finally, we show capabilities in defining local defects and demonstrate proof-of-principle applications in spectrally selective perfect reflectors and chiral light discriminators.

Exploring the Multifunctional aspects of SrBi2-X(CoFe2O4)XNb2O9 Nanocomposite Materials Emphasizing the Structural, Elastic, and Optical Properties

Nanocomposites of SrBi(2-X)(CF)XNb2O9 (SBNCF) (CF=CoFe2O4 for X = 0.0 to 0.5 with a step increment of 0.1) were synthesized using the hydrothermal method and characterized for their structural, morphological, elastic, and optical properties. The incorporation of CF into SrBi2Nb2O9 (SBN) resulted in hybrid composites with tailored properties. X-ray Diffraction (XRD) with Rietveld refinement analysis confirmed the formation of orthorhombic SBN and spinel CF phases. Field Emission Gun Scanning Electron Microscopy (FEG-SEM) revealed that SBN exhibits a plate-like morphology, with the incorporation of CF into the SBN matrix resulting in both plate-like and octahedral-shaped grains. The Brunauer–Emmett–Teller (BET) method was used to determine the pore radius and surface area, both of which were found to have increased, indicating an enhancement in photocatalytic performance. The presence of the constituent elements in the prepared compositions was confirmed by Energy Dispersive Spectroscopy (EDS). Fourier Transform Infrared Spectroscopy (FTIR) spectra were used to determine elastic properties, suggesting potential applications in electronic noise filtering. From Diffuse Reflectance Spectroscopy (DRS), a recognizable semiconducting behavior and band gap bowing were noticed in SBNCF nanocomposites on the obtained energy band gap values (2.20 eV - 1.56 eV) compared to the SBN host matrix (3.16 eV). The materials exhibited strong emission peaks at 470 nm, 528 nm, 584 nm, and 703 nm upon the excitation of 425 nm light using Photoluminescence (PL) spectroscopy. The white emission was predominant at room temperature in all the produced samples and the corresponding color temperature values range from 5865.93 K to 7599.05 K from the CIE diagram. The SBNCF materials are promising candidates in photocatalytic reactions and white light-emitting diodes (w-LEDs) based on their enhanced optical properties.

Density functional theory study of influence of impurity defects on structure and properties of cassiterite

Using density functional theory (DFT), geometric optimizations were performed on the supercell systems of undoped cassiterite and 24 types of doped cassiterite with metals such as Sc, Ti, V, etc. The lattice constants, band structures, and electronic density of states (DOS) were calculated to investigate the crystal structure and electronic properties of cassiterite. The results indicate that the presence of impurity defects leads to varying degrees of distortion in the lattice angles and unit cell of cassiterite crystal. Doping with Ti and Al increases the semiconductor band gap of cassiterite, while other impurity-doped cassiterite decreases the band gap. The impurity-doped cassiterite band gap gradually decreases with increasing atomic number, exhibiting semiconductor-to-metal transition in the doped cassiterite. The overall DOS of cassiterite doped with Nb, Mo, Ta, W, As, Sb and Bi shifts to the direction of low energy, and the oxidation capacity of cassiterite is enhanced.

In Situ growth of high-crystallinity MOF@CTF core-shell hybrid heterostructures and their application in photoelectrochemical sensing of vancomycin

Vancomycin is a first-line drug for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant bacterial infections. It is of great significance to develop rapid detection methods for vancomycin in different matrices. In this work, a novel method for the in-situ preparation of MOF@CTF core-shell hybrid heterogeneous structures was proposed and applied to the photoelectrochemical detection of vancomycin. The insolubility of the imine precursor structure in homogeneous solvents and the Lewis acidic centers in the MOF structure induced the initial arrangement of CTF on the surface of PCN-224. By encapsulating a layer of highly crystalline CTF structure onto the initial morphology of PCN-224, a MOF@CTF heterogeneous structure was formed. Importantly, the introduction of anthracene-based electron-donating groups into the CTF structure and the formation of a donor-acceptor system with triazine rings enhanced the photoconversion efficiency of the heterogeneous structure by establishing a continuous separated built-in electric field within the core-shell structure. The successful in-situ synthesis of the core-shell hybrid heterogeneous structure was confirmed through microscopic morphology, PXRD, XPS, and FT-IR. Furthermore, investigations into the semiconductor properties of the heterogeneous structure, including semiconductor type, bandgap, and photo-voltage, were conducted. Results showed that the heterogeneous structure exhibited a doubled photocurrent density compared to the original PCN-224. Additionally, a molecularly imprinted photoelectrochemical sensor (MIPECS) for vancomycin was constructed. Under optimized conditions, the sensor demonstrated a superior concentration response range (0.1 nM - 1 μM) and detection limit (0.031 nM, 3σ/S, n = 11). Simultaneously, the potential applicability of the sensor in animal-derived foods, serum, and environmental water samples was evaluated, yielding satisfactory results.

Composition-Regulated Photocatalytic Activity of ZnIn2S4@CdS Hybrids for Efficient Dye Degradation and H2O2 Evolution.

Heterostructures of visible light-absorbing semiconductors were prepared through the growth of ZnIn2S4 crystallites in the presence of CdS nanostructures. A variety of hybrid compositions was synthesized. Both reference samples and heterostructured materials were characterized in detail, regarding their morphology, crystalline character, chemical speciation, as well as vibrational properties. The abovementioned physicochemical characterization suggested the absence of doping phenomena, such as the integration of either zinc or indium ions into the CdS lattice. At specific compositions, the growth of the amorphous ZnIn2S4 component was observed through both XRD and Raman analysis. The development of heterojunctions was found to be composition-dependent, as indicated by the simultaneous recording of the Raman profiles of both semiconductors. The optical band gaps of the hybrids range at values between the corresponding band gaps of reference semiconductors. The photocatalytic activity was assessed in both organic dye degradation and hydrogen peroxide evolution. It was observed that the hybrids demonstrating efficient photocatalytic activity in dye degradation were rather poor photocatalysts for hydrogen peroxide evolution. Specifically, the hybrids enriched in the CdS component were shown to act efficiently for hydrogen peroxide evolution, whereas ZnIn2S4-enriched hybrids demonstrated high potential to photodegrade an azo-type organic dye. Furthermore, scavenging experiments suggested the involvement of singlet oxygen in the mechanistic path for dye degradation.

A New Technology for Industrial Strain Mapping Using Single-Wall Carbon Nanotube Sensors

Measurements of mechanical strain are widely used in heavy industry to design and test new structures and to ensure the safety of installed infrastructure. However, the few practical methods for strain measurement all have serious limitations. To complement these methods, we have developed a new strain technology, called S4 for “strain-sensing smart skin,” which uses single-wall carbon nanotubes (SWCNTs) as microscopic sensors. Nanotubes dilutely embedded in a polymer are applied as a thin film to specimen surfaces of interest. Subsequent strains in the specimen are transmitted by load transfer through the film to the nanotubes, inducing axial compression or extension. Those small structural deformations of the SWCNTs alter the semiconducting band gaps in predictable ways, causing proportional shifts in the peak wavelengths of their near-infrared fluorescence emission. Shifts are quantified by optically exciting the specimen surface and spectrally analyzing the resulting fluorescence to deduce strain values at the probed locations. The S4 method has recently been implemented using hyperspectral imaging. We demonstrate measurements in less than one minute of strain maps containing hundreds of thousands of pixels with 50 microstrain noise levels and 0.2 mm spatial resolution. This technology has promising potential to become a large-scale commercialized application of carbon nanotechnology.

(Invited) Resolving Catalytic Mechanism at an Electrode Surface: Thermodynamics & Kinetics of Reaction Steps

Computationally, often the energetics of intermediate reaction steps differentiate the efficiency of heterogeneous catalysts for product evolution. Yet, when compared to experiment, kinetic models are applied. For example, a material’s activity measured by one rate of product evolution is plotted as a function of the calculated formation energies of intermediate chemical forms. A critically important reaction for which this dichotomy between experiment and theory exists is the oxygen evolution reaction (OER) from water. In the laboratory group, we employ time-resolved optical and vibrational spectroscopy to deconstruct OER into its individual reaction steps on an electrode surface. In the presentation, I will describe the experimental methodology and the chosen model system, the n-doped SrTiO3/aqueous interface. I’ll show how these experiments identify both the rates and energetics of the first reaction step, the release of a proton and electron from an absorbed water species, denoted by OH* or O*. A recent success was to isolate a Langmuir isotherm of the intermediate population arising within < 2 ps on the SrTiO3 surface. The intermediate population is of trapped holes measured by emission from the conduction band into unoccupied states in the middle of the semi-conductor bandgap. The isotherm is tuned by the pH of the electrolyte. The pH-dependent formation of these intermediates are connected to their pH-dependent decay at microsecond timescales, presumably related to later reaction steps of OER. I'll also present work on the side of vibrational spectroscopy that looks at how the potential energy surface of a particular trapped hole, the terminal oxyl radical, arises in time through the spectral kinetics of its normal mode. A growing area is to apply the particular experimental methodology to a surface of similar electronic structure but diverse crystal geometries, namely polymorphs of TiO2.

Deep learning tight-binding approach for large-scale electronic simulations at finite temperatures with ab initio accuracy

Simulating electronic behavior in materials and devices with realistic large system sizes remains a formidable task within the ab initio framework due to its computational intensity. Here we show DeePTB, an efficient deep learning-based tight-binding approach with ab initio accuracy to address this issue. By training on structural data and corresponding ab initio eigenvalues, the DeePTB model can efficiently predict tight-binding Hamiltonians for unseen structures, enabling efficient simulations of large-size systems under external perturbations such as finite temperatures and strain. This capability is vital for semiconductor band gap engineering and materials design. When combined with molecular dynamics, DeePTB facilitates efficient and accurate finite-temperature simulations of both atomic and electronic behavior simultaneously. This is demonstrated by computing the temperature-dependent electronic properties of a gallium phosphide system with 106 atoms. The availability of DeePTB bridges the gap between accuracy and scalability in electronic simulations, potentially advancing materials science and related fields by enabling large-scale electronic structure calculations.

Computational Prediction of Structural, Optoelectronic, Thermodynamic, and Thermoelectric Response of the Cubic Perovskite RbTmCl3 via DFT‐mBJ + SOC Studies

Perovskite halides, owing to their environmental stability, non‐toxicity, and remarkable efficiency, are emerging as potential candidates for photovoltaic, solar cell, and thermodynamic applications. The electronic, optical, thermoelectric, and thermodynamic properties of cubic perovskite RbTmCl3 are studied using density functional theory (DFT). The electronic, optical, and thermoelectric properties are calculated both with and without spin‐orbit coupling (SOC) using the Tran and Blaha functional in the structure of the modified Becke Johnson (mBJ) exchange potential, while structural and mechanical properties are assessed using the exchange‐correlation functional calculated using the Perdew Burke Ernzerhof Generalized Gradient Approximation (PBE‐GGA). The negative formation energy (−592.39 KJ mol−1) and tolerance factor (1.17) for structural stability and current their existences in the cubic phase are found. Evaluation of the obtained data with and without SOC shows that the SOC effect causes the Tm‐d states to be shifted toward the level of Fermi, thereby decreasing the energy band gaps from 1.42 to 1.32 eV. Nevertheless, only the shift of the third variable peak to lower energies indicates the impact of SOC on optical properties. The effectiveness of RbTmCl3 in optical devices operating in the visible and ultraviolet regions is demonstrated by the exceptional absorption of light in these ranges. Using TB‐mBJ + SOC functional, the electronic band structure research reveals a direct semiconducting band gap of 1.32 eV in comparison to earlier calculations like LDA, PBE‐GGA, and TB‐mBJ. The absorption spectrum, reflectivity, extinction coefficient, refractive index, and dielectric function are displayed in addition to the electrical properties. Additionally, the quasi‐harmonic Debye model, which accounts for lattice vibrations, was used to study the corresponding volume, heat capacity, expansion of the heat coefficient, and Debye temperature of the RbTmCl3 crystal. We have calculated the thermoelectric parameters such as the Seebeck coefficient, thermal conductivity, electrical conductivity, and power factor as a function of temperature (100–900 K).

Preparation, Structures, Photoluminescence and Semiconductive Properties of Two Novel Lanthanide Mercury Materials with a 3-D Framework Structure.

Two novel lanthanide mercury materials, [Gd(IA)3(H3O)2Hg3Br6]n·2nCl (1) and [La(IA)3(H3O)2Hg3Br6]n·2nCl (2) (IA = isonicotinic anion), have been prepared under solvothermal conditions and characterized by single-crystal X-ray diffraction techniques. They are isomorphic and characterized by a three-dimensional (3-D) framework structure. The lanthanide ions are bound by eight oxygen atoms to exhibit a square antiprismatic geometry. The solid-state photoluminescence experiment discovers that compound 1 shows a strong emission in the red region. Compound 1 possesses CIE (Commission Internationale de I'Éclairage) chromaticity coordinates of 0.7347 and 0.2653. Its CCT (correlated color temperature) is 6514 K. Compound 2 displays yellow photoluminescence and it has CIE chromaticity coordinates of 0.4411 and 0.5151. The CCT of compound 2 is 3633 K. Solid-state UV/Vis diffuse reflectance spectra revealed that their semiconductor band gaps are 2.16 eV and 2.85 eV, respectively.

Contribution of individual phonon to the band gap renormalization in semiconductors

Understanding the origin of temperature-dependent bandgap in semiconductors is essential for their applications in photovoltaics, optoelectronic and space applications. In this regard the electron–phonon coupling is known to play a crucial role in the temperature dependence of the bandgap of semiconductors. Several models have also been proposed in this regard which are also found experimentally compatible; however, these models need to account for more information about the contribution of individual modes in band gap renormalization. The present report is an analytical attempt to do so by utilizing the Bose–Einstein oscillator model, thereby discussing a method for finding the individual renormalization term contributed by respective phonon modes to the overall bandgap. This study contributes to the fundamental understanding of the temperature variation of optical properties of semiconductors that correlates with the role of electron–phonon interaction.