Journal of Electronic Materials最新文献

Two-dimensional (2D) GeTe is a popular medium-temperature thermoelectric material, but few studies have focused on strategies for improving its thermoelectric performance. To further investigate the thermoelectric properties of two-dimensional GeTe, different atomic defects are introduced, and the electronic structure and thermoelectric properties are systematically investigated via first-principles calculations and the semiclassical Boltzmann theory. Compared with that of three-dimensional (3D) GeTe, the Seebeck coefficient of 2D GeTe increases from 144 μV K⁻¹ to 560 μV K⁻¹ at 700 K, and the thermal conductivity decreases from 3.3 W m⁻¹ K⁻¹ to 2.3 W m⁻¹ K⁻¹. Thus, the ZT value increases from 0.8 to 1.14. On the basis of these results, the influence of vacancy atomic defects on the thermoelectric performance is investigated. With single-atom defects (SV-Ge and SV-Te), the ZT value increases at constant temperature. However, for double-atom defects in monolayer GeTe, the ZT value increases when DV-585 defects are present but decreases to varying degrees when DV-Ge and DV-Te defects are present. The ZT value of monolayer GeTe with DV-585 defects has an average increase of 0.56 at 300–800 K, which accords well with the experimental results. This study indicates that introducing single-atom vacancy defects somewhat improves the thermoelectric performance of monolayer GeTe, which provides an important point of reference for the development of GeTe in the two-dimensional materials field.

The interaction of a sensitive oxide with a target gas determines its chemiresistive signal; however, the lack of a fundamental theoretical model currently hinders its wide application. In this work, CuScO₂ microsheets are synthesized by a simple hydrothermal method, which brings about the first oxide-based acrylic acid gas sensor. It exhibits high selectivity for acrylic acid, outperforming other volatile organic compound (VOC) gases, including methanol, ethanol, formaldehyde, toluene, acetonitrile, and acetone, with a high response (up to 7–10 ppm acrylic acid) and an ultralow detection limit down to sub-ppm level (14 ppb) at a low operating temperature of 160°C. Compared to the chromatographic techniques, the proposed CuScO₂ gas sensor represents a prominent chemiresistive effect favorable for the simple and efficient monitoring of acrylic acid gas, which is significant for human health. In addition, the remarkable gas sensing properties of CuScO₂ are elucidated by a new mechanism based on the results of microstructural characterization and first-principles calculations followed by energy band analysis. Instead of the classic ambient oxygen ionosorption, Cu and Sc atoms on the solid surface play the crucial roles in target gas adsorption and electron transfer procedures, respectively. Such synergistic effect of metal atoms offers a new perspective for the design of material systems for advanced gas sensing devices.

Judd–Ofelt analysis and photoluminescence study of akermanite-structured Sm³⁺ -doped Ca₂MgSi₂O₇ phosphor synthesized by combustion synthesis followed by a solid-state reaction process is presented. PXRD confirmed the tetragonal structure with the P-4 21 m (No.113) space group. SEM, EDS, and elemental mapping confirmed the morphology and composition. The photoluminescence (PL) emission spectra indicate that the phosphor gives orange-red emissions at 603 nm attributed to ⁴G_5/2 (to ) ⁶H_7/2 transition. Optimum concentration has been found to be 0.4 mol%. The CIE chromaticity coordinates are 0.57, 0.43. The branching ratio with respect to the transition, ⁴G_5/2—⁶H_7/2 has been found to be around 53%, suggesting it as a potential laser material in addition to its use for designing white LED phosphors.

A series of superconducting samples including pure Bi₂Sr₂Ca₂C₃O₁₀ (BSCCO), Pb-doped BSCCO (Bi_1.35Pb_0.65Sr₂Ca₂Cu₃O₁₀), Mg-doped BSCCO (Bi_1.65Mg_0.35Sr₂Ca₂Cu₃O₁₀), and optimally co-doped Pb-Mg-BSCCO with an optimal formula of BiPb_0.65Mg_0.35Sr₂Ca₂Cu₃O₁₀ (108K superconductor) were carefully synthesized and optimized with a maximum ratio of incorporated lead and magnesium, achieving both quality of structural features and an improved T_c offset of 108 K. The optimized porous sample was well characterized via x-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), and three-dimensional atomic force microscopy (3D-AFM). In addition, the Brunauer–Emmett–Teller (BET) specific surface area was estimated at 11.9 m²g⁻¹. Porous Mg-doped BPSCCO exhibited high performance efficiency for H₂ storage, recording maximum H₂ uptake of 5.92 wt.% at a temperature of 270°C and pressure of 14 bar. A mechanism of loaded hydrogen was proposed. Magnesium and lead incorporated in 2223-BPSCCO were suggested to play a vital role in hydrogen storage as Mg hydride and Pb as plumbane.

Graphical Abstract

In this work, the elastic properties of two tellurite glass series 80TeO₂-(20−x)WO₃-xBi₂O₃ (80TeWBi) and 70TeO₂-(30−x)WO₃-xBi₂O₃ (70TeWBi) (where x = 0 mol.%, 5 mol.%, and 10 mol.%) were quantitatively analyzed and predicted. Many structural and compositional parameters, including the density of network bonds, mean cross-link density, average bond-stretching force constant, total packing density, and dissociation energy per unit volume, were calculated using bond compression (BC), ring deformation (RD), and Makishima–Mackenzie (M–M) models. These parameters were correlated with experimental elastic properties to explore the structural role of WO₃ and Bi₂O₃ in the tellurite network. It was found that WO₃ enters the tellurite network of Bi₂O₃-free 80TeO₂-20WO₃ and 70TeO₂-30WO₃ glasses as a network former. This stiffened the structure through the formation of WO₄ tetrahedral units, WO₆ octahedral units, and Te–O–W linkages. As a result, the theoretical bulk modules (K_bc) increased from 73.23 GPa to 83.90 GPa whereas the theoretical Poisson's ratio decreased from 0.235 to 0.225 with increasing WO₃ mol.%. Meanwhile, Bi₂O₃ enters the network of TeO₂-WO₃-Bi₂O₃ glasses as a network modifier. This weakens the glass structure and results in the transformation of some TeO₄ trigonal bipyramids into TeO₃ trigonal pyramids by breaking the Te–O–W linkages and creating non-bridging oxygen atoms. Excellent agreement was achieved between the theoretical and experimental values of elastic moduli and Poisson's ratio.

BiFe_0.91Zr_0.09O₃ (9BFZrO)/LaNiO₃ (LNO)/MgO and 9BFZrO/LNO/Si multilayers were prepared by the sol–gel method using MgO and Si single crystals as substrates, and LNO films with a thickness of approximately 50 nm were deposited by magnetron sputtering to form bottom electrodes and transition layers. The effects of different substrates on the crystal structure, phase composition, oxygen vacancy content, ferroelectric properties, dielectric properties, leakage mechanism, and ageing properties of the 9BFZrO films were systematically analysed. X-ray diffraction showed that the prepared 9BFZrO thin films had a structure composed of both rhombic R3c and orthogonal Pnma phases, and the films prepared on the MgO substrate contained a significant amount of the R3c phase. SEM analysis showed that the thin film prepared on the MgO substrate had a relatively large grain size. X-ray photoelectron spectroscopy showed that the Fe²⁺ content and oxygen vacancy defect concentration of the MgO substrate samples were relatively low. The thin film prepared on the MgO substrate has a high residual polarization strength (2P_r = 60.28 μC/cm²) and a low leakage current density (4.71 × 10⁻⁶ A/cm²). After 90 days of room-temperature ageing, the residual polarization strength (2P_r) of the film on the MgO substrate decreased by 16.8%, with a lower ageing degree and better stability.

There is a pressing need for investigations of solar conversion systems to enhance and perfect the use of this expandable energy resource. This necessitates additional research on the development of solar cells, which are the mainstay of these systems. In this regard, the purpose of this study is to examine, using numerical modeling, the impact of cell temperatures in the range of 270–340 K on solar cell performance and efficiency. Two configurations are considered based on different overlapping materials. A solar cell type ZnO/a-Si(n)/a-Si(p) (single-junction) with thickness of 25 nm, 50 nm, and 2500 nm, respectively, and a solar cell type ZnO/GaAs(p)/a-Si(n)/a-Si(p) (double-junction) with thickness of 25 nm, 100 nm, 50 nm, and 2500 nm, respectively, are examined. The electrical characteristics, fill factor (FF), and efficiency (ɳ) are extracted to highlight the results of the present study. Numerical analysis was performed using AMPS-1D (One-Dimensional Device Simulation for Analysis of Microelectronic and Photonic Structures), a modeling and analysis program. This analysis enabled the establishment of a causal relationship between the features of the considered solar cells and their corresponding material attributes, and the production process. After different adjustments and refinements, the results for the single-junction cell presented parameter values of ({J}_{text{SC}}=text{32.21 m}) A/cm², ({V}_{text{OC}}=text{0.81 V}), and FF = 0.75, resulting in efficiency of ɳ = 19.58%. For the double-junction cell, the analysis revealed parameter values of ({J}_{text{SC}}=text{37.75 mA}/{text{cm}}^{2}), ({V}_{text{OC}}=text{0.789 V}), and FF = 0.86, corresponding to efficiency of ɳ = 25.70%.

This study investigates the synthesis of heavy-metal-free AgInS₂ quantum dots (QDs) using a facile successive ionic layer adsorption and reaction (SILAR) method, exploring their application in quantum dot-sensitized solar cells (QDSSCs). The AgInS₂ QDs were grown on mesoporous TiO₂ via a two-stage SILAR process at room temperature. The optimization of Ag-S SILAR cycles (n) was performed to determine the ideal conditions, while the In-S SILAR cycles were held constant at seven cycles. X-ray diffraction (XRD) pattern analysis revealed an orthorhombic crystalline structure of the synthesized AgInS₂ QDs. Analysis of the optical spectra revealed a reduction in the optical energy bandgap (E_g,op) of AgInS₂ QDs from 2.00 eV to 1.92 eV and further to 1.78 eV as the value of n increased from 1 to 3. Employing AgInS₂ QDs, a polysulfide electrolyte, and a CuS counter electrode, liquid-junction semiconductor QDSSCs were fabricated. Optimal conditions were achieved at n = 2, resulting in outstanding power conversion efficiency (PCE) of 3.57% (J_sc = 8.56 mA/cm², V_oc = 0.64 V, FF = 65.2%). Under reduced light intensity (0.25 sun), the PCE increased to 5.26%. The external quantum efficiency (EQE) spectrum of the best cells spanned 400−700 nm, maintaining a nearly constant EQE value of ~ 65% within the 400−600 nm range. Remarkably, the PCE achieved surpassed previously reported liquid-junction AgInS₂ QDSSCs. These findings highlight the facile production of heavy-metal-free AgInS₂ QDs through a room-temperature SILAR method and the tunable optical properties of AgInS₂ QDs by controlling Ag-S SILAR cycles, revealing their potential as an efficient solar absorber.

Graphical Abstract

Inorganic lead-free metal halide perovskites are being rigorously explored as a substitute for organic lead-based materials for various energy device applications. Germanium as a replacement for lead has been proven to give exemplary results theoretically, and there have been promising results. The current work presents the investigation of CsGeI₃ (CGI) polycrystals grown using a solution-free melt-growth technique with low-cost precursors. A soak-ramp profile was designed to synthesize polycrystalline powders, which were evaluated for stability. X-ray diffraction and Raman spectroscopy analysis suggest the formation of CsGeI₃ perovskite powders, matching the reported literature. Diffuse reflectance spectroscopy measurements showed the bandgap of the polycrystals to be around 1.6 eV. A prominent photoluminescence peak was obtained at 767 nm. The powders were examined using thermogravimetric analysis to assess the thermal degradation pathways. The as-grown inorganic perovskite polycrystals were relatively stable during storage under ambient conditions. Theoretical studies were also carried out to support the experimental data. Calculations were performed with different approximations, including local density approximation (LDA), generalized gradient approximation (GGA), and Heyd–Scuseria–Ernzerhof (HSE) approximation, out of which the HSE approximation yielded the most accurate results that matched the experimental findings. Moreover, for the CGI device with Ag electrodes simulated using SCAPS-1D software, highest incident photon-to-electron conversion efficiency was observed. The obtained optical and structural properties indicate the suitability of the synthesized CsGeI₃ perovskite polycrystals for photovoltaic applications, specifically solar cells and light-emitting diodes.

In this work, the synthesis of Ho³⁺-doped calcium titanate perovskite (CaTiO₃) revealed significant photoluminescence (PL) properties, predominantly displaying a distinct green emission. The investigation explored Ho³⁺-doped CaTiO₃ perovskite synthesized via the sol–gel method. Structural analysis confirmed an orthorhombic crystal structure through powder x-ray diffraction (XRD) and Rietveld refinement, while Fourier transform infrared (FT-IR) spectroscopy confirmed the presence of functional groups in Ho³⁺-doped CaTiO₃. Diffuse reflectance spectroscopy (DRS) revealed a charge transfer band between O²⁻ and Ho³⁺ ions in the range of 250–350 nm, supported by photoluminescence excitation (PLE) spectra. A bandgap of 3.39 eV was found for Ho³⁺-doped CaTiO₃. At 0.03 mol Ho³⁺, the PLE band intensity was saturated, indicating optimal excitation efficiency. Emission spectra revealed distinct intra 4f–4f transitions, particularly a green emission at 545 nm under 454 nm excitation corresponding to ⁵F₄ + ⁵S₂ → ⁵I₈ transition. The PL intensity reached its peak at 0.03 mol Ho³⁺ and then decreased due to concentration quenching. Color purity reached ~90%, highlighting its potential in applications requiring precise green emission. The results of the study suggest that this perovskite is well suited for optoelectronics, lighting, displays, or industries that require specific green light emission properties.