The power conversion efficiency of perovskite solar cells has increased rapidly; however, interfacial-defect-induced non-radiative recombination, ion migration, and sensitivity to moisture, oxygen, and thermal stress continue to cause open-circuit voltage losses and a limited operational lifetime. Owing to its tunable energy levels, high carrier mobility, and compact hydrophobic layered structure, two-dimensional MoS2 can serve as an electron or hole transport layer, an interfacial buffer layer, or an additive, enabling favorable energy-level alignment and optimized interfacial charge-transfer kinetics, thereby promoting carrier extraction and suppressing recombination. The sulfur sites of MoS2 can coordinate with undercoordinated Pb2+ to form Pb–S bonds, thereby passivating defects and stabilizing the α-FAPbI3 phase, while continuous MoS2 layers can suppress ion migration through physical diffusion blocking; meanwhile, van der Waals epitaxy and heterogeneous nucleation induced by MoS2 improve film crystallinity and relieve residual stress, synergistically enhancing both efficiency and durability. This review summarizes the functional mechanisms, preparation methods, and integration routes of MoS2 in PSCs, with particular attention to recent advances in wafer-scale monolayer interfaces, mesoporous electron-transport layers, functionalized nanosheet additives, quantum-dot composite absorbers, and hybrid interfaces. These approaches are compared in terms of their effects on charge transport, defect passivation, crystallization, device efficiency, stability, process compatibility, and scalability. The outlook also considers data-driven optimization, integration with other two-dimensional materials, and applications in flexible, large-area, and tandem devices.
Transition metal dichalcogenides (TMDs) and transition metal trichalcogenides (TMTCs) exhibit tunable electronic properties, and when stacked together in their two dimensional (2D) forms, they can display distinctive electronic properties beyond those of conventional heterostructures. In this study, we fabricated for the first time junction field effect transistor (JFET) by stacking MoSe2, a transition metal dichalcogenide (TMD), with ZrSe3, a transition metal trichalcogenide (TMTC). We characterized its electrical properties, where the device’s electrical characteristics were analyzed based on the stacking sequence. Two device configurations top-gate and bottom-gate JFETs were fabricated and systematically analyzed. Notably, the top-gate JFET exhibited superior performance, with transconductance (gm) reaching 12.8 μS, carrier mobility up to 366.95 cm2/Vs, and a subthreshold swing (SS) of 13.25 V/dec, significantly outperforming the bottom-gate configuration. The successful demonstration of this device not only establishes the feasibility of MoSe2/ZrSe3 heterojunctions for high performance JFET applications but also paves the way for next generation electronic devices based on engineered 2D heterostructures.
This study investigates the structural evolution and DC electrical properties of Pb50−xGexTe50 ternary chalcogenide alloys with varying germanium concentrations (x = 5, 10, 15, 20). Synthesized via the melt-quenching technique, the alloys were characterized using Scanning Electron Microscopy (SEM) and temperature-dependent electrical resistivity measurements within the range of 290–475 K. Microstructural analysis revealed that increasing Ge substitution significantly promotes matrix densification, reducing porosity and improving inter-granular connectivity. The DC conductivity exhibits a systematic increase with Ge content up to x = 15, attributed to the increased density of defect states. For instance, as Ge content increases from x = 5 to x = 15, the DC conductivity increases, corresponding to an activation energy (ΔE1) shift from 0.203 eV to 0.281 eV at high temperatures. However, for the sample with x = 20, a non-monotonic shift in conductivity parameters is observed, evidenced by a significant reduction in the pre-exponential factor ( σ01 ) compared to the intermediate compositions, which indicates a alteration in the conduction pathways. The conduction data were analyzed using the Mott and Davis model, identifying three distinct mechanisms: hopping between localized states near the Fermi level at low temperatures, hopping within band-tail states at intermediate temperatures, and excitation into extended states at high temperatures. Furthermore, calculations of the density of states (DOS) indicated that Ge incorporation increases the density of extended and localized states while simultaneously narrowing the band tail width ( ΔE ), thereby reducing structural randomness. These findings highlight the efficacy of germanium doping in tuning the electronic structure of Pb-Ge-Te alloys, suggesting their suitability for advanced optoelectronic and semiconductor applications.
Nanopowder copper sulphide CuS has been synthesised successfully via the chemical bath deposition method. Two samples of precipitated CuS nanopowder were prepared at molar concentration of 0.5 M from [CuSO4·5H2O and Na2S2O3·5H2O] and 0.05 M from [Na2EDTA·2H2O]. Both samples were annealed at 150°C for one hour in air. The effects of washing and nonwashing on the structural, morphological, and compositional properties were studied. The X-ray diffraction (XRD) patterns showed that both samples have a CuS hexagonal structure with lattice constants (a = 3.773 Å , c = 16.398 Å ), and (a = 3.792 Å , c = 16.534 Å ), also the average crystallite size was found (11.4 nm, 4.5 nm) without washing and washing, respectively. Secondary phases Na2EDTA-Cu complex impurity, CuSO4·5H2O and Cu2O were showed in both samples and the intensity of peaks were reduced after washing. Field emission scanning electron microscopy (FESEM) analysis showed that the precipitated nanopowder has aggregated into hollow microsphere-like structures, resembling Bucky spheres, with average nanoparticle sizes of 62 nm and 58 nm for n-CuS and w-CuS, respectively. EDS analysis showed real and secondary phase values (15% and 85%) for the precipitated nanopowder without and with washing, respectively. The obtained results CuS nanopowder with high purity can be utilised in various photovoltaic applications.
Semiconductor quantum dots (QDs) with tunable narrow bandgaps have emerged as promising materials for next-generation near-infrared (NIR) optoelectronic and photovoltaic devices because their optical properties can be tailored through composition and quantum confinement. Among IV–VI chalcogenide nanomaterials, quaternary alloy systems provide greater compositional flexibility than conventional binary and ternary counterparts; however, PbSnSeS quantum dots remain largely unexplored despite their potential for broadband infrared applications. Here, the structural, electronic, and optical properties of PbSnSeS quaternary QDs synthesized by a one-pot colloidal hot-injection method are systematically investigated. The crystalline IV–VI chalcogenide phase and successful quaternary alloy formation were confirmed by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX), while scanning electron microscopy (SEM) revealed particle sizes in the range of 6–20 nm. The composition- and size-dependent optical behavior was further interpreted using the L.E. Brus model, hyperbolic band model, compositional bandgap estimation, exciton Bohr radius analysis, and density-of-states (DOS) calculations. UV–Vis–NIR spectroscopy exhibited a strong absorption peak at approximately 1675 nm, corresponding to an optical bandgap of 0.74 eV, whereas photoluminescence measurements showed intense NIR emission centered near 1650 nm with a relatively narrow linewidth. The combined theoretical and experimental results demonstrate tunable optical characteristics spanning the visible to near-infrared spectral region. Although lead-containing quantum dots raise environmental concerns, partial substitution of Pb with Sn provides a comparatively lead-reduced alloy while retaining favorable narrow-bandgap optical properties. Overall, the findings identify PbSnSeS quaternary quantum dots as promising candidates for near-infrared optoelectronics, infrared photonics, and next-generation tandem solar cell applications.
Sodium metal batteries stand as a highly promising electrochemical energy storage system; however, their commercialization is severely impeded by challenges such as anode dendrite formation, the shuttle effect of highly reactive intermediates at the cathode, electrode volume expansion, and interfacial instability. Owing to their high electronic conductivity, high theoretical specific capacity, and superior sodiumphilic affinity, tellurium and its tellurides have emerged as pivotal functional materials for enhancing the performance of sodium metal batteries. This study reviews the advancements in their applications within sodium metal batteries, elaborates rational design strategies carbon-based composites, alloying, and heterostructure construction for cathode functional materials, analyzes their mechanisms in optimizing sodium ion migration kinetics and synergistically regulating the solid electrolyte interphase (SEI) layer at the anode interface, and summarizes full-cell performance optimization strategies such as eutectic acceleration, defect engineering, and multicomponent synergy regulation. Additionally, it critically analyzed such as the scarcity of tellurium resources, inadequate long-term cycling stability of materials, and ambiguous reaction mechanisms. Furthermore, it outlines future research directions in terms of resource utilization, mechanism investigation, structural design, and process optimization, providing significant guidance for research and development in this field.
In this work, Ge45As40Se15 chalcogenide glass was prepared using spark plasma sintering. This method synthesizes glass powder into blocks through a certain temperature and pressure, which is an effective densification and high-precision molding of infrared transparent blocks and lenses. Through X-ray diffraction (XRD) and differential scanning calorimetry analysis, we tracked the gradual evolution of the powder during ball milling and observed the existence of a glass transition temperature in the glass after powder hot pressing. This method can prepare components outside the conventional glass forming region with high hardness and infrared transmittance, providing a simple and economical synthetic approach for preparing chalcogenide glass materials with optical application potential.
We report on electron-beam evaporated As2Se3 films for far-infrared heterogeneous metalenses. The films exhibit a structurally relaxed network compared to bulk glass, evidenced by XRD and Raman spectroscopy, leading to enhanced infrared transmittance, reduced refractive index, and lower glass transition temperature. However, thermal expansion mismatch induces cracking in thick films under thermal cycling. The As2Se3/BaF2 system shows superior adhesion due to minimal mismatch (Δα < 2.5 × 10-6 ºC-1). An 8 µm thick film withstands over thirty rapid heating and liquid nitrogen quenching cycles without degradation, while maintaining subwavelength thickness suitable for metalens design. These results demonstrate the As2Se3/BaF2 platform as a robust candidate for environmentally stable infrared metasurfaces.
The major challenge in developing efficient photovoltaic devices is achieving highlight absorption, optimal charge transport, and low recombination losses. In this work, the effect of the immersion bath numbers in the chemical bath deposition (CBD) technique on the properties of bismuth oxysulfide (Bi2O2S) thin films, as emergent materials, was studied. The films were synthesized under eco-friendly conditions, using a low-concentration bismuth nitrate precursor and thioacetamide as the sulfur source, and under basic conditions at moderate temperature, with a reaction time of 3 h. X-ray diffraction demonstrated the formation of a crystalline Bi2O2S phase, and the morphological analysis showed a uniform film coverage with flower-like morphology, indicating anisotropic growth. XPS verified the coexistence of bismuth, oxygen, and sulfur, confirming the formation of the oxysulfide compound. Results demonstrated that absorbance increased as the number of immersion bath numbers increased. Indeed, structural analysis established that the number of immersion baths critically influences crystallite size, interlayer spacing, and crystallinity of Bi2O2S nanosheets. Finally, a formation mechanism is proposed for these Bi2O2S thin films for the one-, two-, and three-immersion bath. This study demonstrates that CBD processing parameters critically influence film quality and phase purity, offering an effective and low-cost route to produce Bi-based thin films with potential applications in photovoltaic devices.
Photocatalytic H2O2 synthesis from O2 is a green and environmentally friendly route. However, due to the limitations of quick recombination of photogenerated electrons and limited O2 activation ability, photocatalytic reactions often exhibit low efficiency. In this study, Zn vacancy-engineered Zn0.4Cd0.6S (ZnV-ZCS) photocatalysts were successfully constructed via a hydrothermal strategy using L-cysteine as a coordination agent. The optimized ZnV-ZCS-10 catalyst achieves an impressive H2O2 production rate of 44.39 mmol/g within 1 h under 425 nm irradiation, approximately 2.3 times higher than that of pristine Zn0.4Cd0.6S (ZCS). Structural characterization and cycling performance tests confirm that the introduction of Zn vacancies does not alter the pristine hexagonal crystal phase of the material, demonstrating good stability. Photoelectrochemical and spectroscopic analyses reveal that Zn vacancies effectively enhance charge carrier separation and reduce charge transfer resistance. Meanwhile, the presence of cation vacancies reconstructs the local electronic environment, promoting the activity of the Zn0.4Cd0.6S catalyst for H2O2 production via the superoxide radical (& sdot;O2-)-mediated pathway. This work highlights the crucial role of cation vacancies in modulating carrier dynamics in sulfide semiconductors for efficient photocatalytic H2O2 production.
An eco-friendly one-pot hydrothermal method was developed to synthesize molybdenum disulfide/graphene oxide (MoS2/GO) nanocomposites for high-performance supercapacitor applications. X-ray diffraction (XRD) analysis confirmed the presence of the MoS2 crystalline phase, with reduced peak intensities upon GO incorporation, indicating suppressed crystallite growth. Scanning electron microscopy (SEM) revealed rod-like MoS2 structures uniformly distributed across layered GO sheets, and energy-dispersive spectroscopy (EDS) confirmed the presence of Mo, S, C, and O elements. Raman and FTIR analyses verified strong interfacial interactions between MoS2 and GO. Brunauer-Emmett-Teller (BET) measurements revealed a mesoporous structure with a specific surface area of similar to 31.7 m(2) g(-1) and a pore size centered at similar to 4 nm, facilitating efficient ion transport. Electrochemical performance evaluated using cyclic voltammetry (CV) in 2 M KOH electrolyte demonstrated a high specific capacitance of 185 F g(-1) at 5 mV s(-1). The quasi-rectangular CV curves and symmetric charge-discharge profiles indicate a combined electric double-layer and pseudocapacitive behavior. The MoS2/GO composite also exhibited improved charge transfer properties and superior cycling stability over 10,000 cycles compared to pristine MoS2. Density functional theory (DFT) calculations revealed that graphene oxide has a higher density of states near the Fermi level than MoS2, indicating enhanced quantum capacitance and faster electron-transfer kinetics. The synergistic integration of MoS2 and GO thus improves conductivity, structural stability, and electrochemical performance. These findings highlight the potential of MoS2/GO nanocomposites as efficient electrode materials tailored for high-performance energy storage devices.
Erbium-doped SnTe (Sn1-xErxTe) single crystals were synthesized to investigate the influence of erbium incorporation on phase stability, crystal structure, and thermophysical behavior relevant to thermoelectric applications. Single crystals with nominal compositions x = 0.00-0.10 were grown using the vertical Bridgman technique under controlled thermal conditions. X-ray diffraction analysis confirmed that at low erbium concentrations (x <= 0.02-0.03), erbium is substitutionally incorporated into the cubic NaCl-type SnTe lattice without detectable secondary phases. At higher erbium contents (x >= 0.05), Er-rich secondary phases such as ErTe and Er2Te3 precipitate within the SnTe matrix, indicating a limited solubility of erbium in SnTe. Differential thermal analysis revealed reproducible thermal effects associated with phase transformations and the formation of secondary phases at elevated dopant concentrations. Scanning electron microscopy combined with energy-dispersive spectroscopy showed microstructural refinement and increased defect density with increasing erbium content. Moderate erbium incorporation enhances phonon scattering, resulting in reduced lattice thermal conductivity and an increased Seebeck coefficient, whereas excessive doping leads to phase instability and degradation of electrical transport. These results demonstrate that erbium acts as an effective dopant for tuning the thermoelectric properties of SnTe within a narrow compositional window, while exceeding the solubility limit induces multiphase behavior and structural instability. The study provides experimentally grounded guidelines for controlled rare-earth doping and phase stability optimization in SnTe-based thermoelectric materials.
Films of (SnS) with a thickness of 400 nm were deposited by the thermal evaporation technique to investigate the influence of annealing temperature on their Physics and CO2 gas-sensing characteristics. The deposited films were annealed at 200, 300, and 400 degrees C. Structural characterization was performed using XRD, and the obtained results revealed that all samples possessed an orthorhombic crystal structure with a preferred orientation (301). The annealing treatment significantly improved the crystallinity of the films and reduced structural defects and lattice strain. Surface morphology investigations were performed using atomic force microscopy (AFM), which revealed noticeable modifications in grain size distribution, surface roughness, and film homogeneity after annealing. Optical characterization was conducted in the range of 300-1100 nm. The optical band gap values were determined using the Tauc method from the (alpha h nu)(2) versus h nu plots and were found to be 1.35, 1.38, 1.62, and 1.40 eV for the as-deposited, 200, 300, and 400 degrees C annealed samples, respectively. Several optical constants, such as the absorption, extinction coefficient, and refractive index, were also evaluated. Furthermore, the CO2 gas-sensing performance of the SnS thin films was examined at operating temperatures of 50, 100, and 150 degrees C. The results demonstrated that both annealing temperature and operating temperature strongly affected the sensitivity and response behavior of the films. Enhanced sensing performance was attributed to improvements in crystallinity, surface morphology, and charge transport properties induced by annealing. The obtained results suggest that annealed SnS thin films are promising candidates for optical and gas-sensing applications.
Copper zinc tin sulfide selenide, Cu2ZnSn(S1-xSex)4, absorbers are promising earth-abundant and environmentally benign materials for low-cost photovoltaic applications. This study investigates the structural and optical properties of Cu2ZnSn(S1-xSex)4 nanostructured thin films prepared by pulsed laser deposition using melt-quenched targets with selenium compositions x = 0.0-1.0. X-ray diffraction revealed that films with low selenium content remained amorphous, whereas higher selenium incorporation promoted the formation of polycrystalline kesterite-stannite phases with preferred orientations along (112), (200), (220), and (312). The crystallite size increased from 12.3 to 17.9 nm as selenium reached x = 1.0, indicating enhanced crystal growth. Atomic force microscopy showed composition-dependent surface evolution, where average roughness decreased initially, reached a maximum of 88.29 nm at x = 0.6, and then declined, reflecting structural reorganization during phase transition. Optical characterization by UV-Vis-NIR spectroscopy demonstrated high absorption coefficients exceeding 104 cm-1 in the visible region, confirming strong light-harvesting capability. The direct optical band gap was tunable between 2.00 and 2.30 eV, with the highest value observed at x = 0.6 due to quantum confinement, nanoscale disorder, and compositional effects. The refractive index, extinction coefficient, and dielectric constants decreased with selenium addition up to x = 0.6, then increased at higher selenium contents, indicating a strong correlation between composition and optical response. The combined results highlight selenium control as an effective route for tailoring phase stability, transparency, and photon management for devices.
Amorphous selenium (a-Se) thin films were deposited by vacuum thermal evaporation and investigated in planar photoconductive structures to evaluate their optical and photoelectrical properties in the low-field regime. SEM analysis showed continuous film coverage with a thickness of about 250 nm. Raman spectroscopy and X-ray diffraction confirmed the amorphous structure of the as-deposited films and the formation of trigonal crystalline selenium after annealing. Optical analysis based on transmission and reflectance spectra yielded an optical band gap Eg = 1.96 eV and an Urbach energy EU = 0.083 eV, indicating localized tail states associated with structural disorder. The planar devices exhibited nearly linear and symmetric dark current-voltage characteristics within |V| <= 10 V, corresponding to an electric field range of 100-1000 V/cm. Under illumination at lambda = 633 nm, the photocurrent showed a sublinear dependence on incident light power density, Iphoto proportional to P lambda gamma, with gamma = 0.55. The responsivity increased with the electric field, which indicates more efficient collection of photogenerated carriers at higher bias. Temperature-dependent measurements over the range 303-343 K showed that both the dark current and the current under illumination increase with temperature, whereas the relative photoresponse decreases because the dark current increases more rapidly. Arrhenius analysis yielded effective activation energies 0.836 eV for the dark current and 0.709 eV for the current under illumination. These results show that the optical disorder parameters and the photoelectrical response are mutually consistent. In weak electric fields, the behavior of planar a-Se films is governed by competition between thermally activated dark conduction and field-assisted collection of photogenerated carriers.
This study focuses on monoclinic system AgSbS2, employing first-principles methods to calculate the structural, mechanical, optical, and thermodynamic properties. Specifically, geometry optimization yields a stable atomic structure with optimized lattice constants (a = 12.82 & Aring;, b = 4.41 & Aring;, and c = 13.19 & Aring;). Furthermore, electronic structure analysis identifies AgSbS2 as a direct bandgap semiconductor with a bandgap of 1.456 eV, where the valence and conduction bands primarily originate from Ag-4d, S-3s, and Sb-5p states. Regarding the elastic properties, the calculated elastic constants, combined with Pugh's B/G criterion, reveal excellent ductility. As for the optical properties, the static dielectric constant epsilon 1(0) is 8.25 and the static refractive index n0 is 2.87. The maximum absorption occurs at a photon energy of approximately 6.62 eV, the maximum reflectivity at about 9.33 eV, and maximum energy loss at 12.17 eV. Finally, the thermodynamic properties are systematically evaluated.
In this study, a lead-free double perovskite solar cell structure based on Cs2BiAgI6 was simulated and optimized to enhance photovoltaic performance. The device architecture follows the configuration: ITO/PCBM/ C60/Cs2BiAgI6/CdTe/Au. The thicknesses of the electron transport layer (ETL), absorber layer, and hole transport layer (HTL) are systematically optimized to evaluate their impact on key performance parameters. The results indicate that optimal performance is achieved with 600 nm thicknesses for all ETLs and HTL, and 2 & micro;m for the Cs2BiAgl6 absorber. Under these conditions, the device exhibits a short-circuit current density of 23.23 mA/cm2, an open-circuit voltage of 1.08 V, and a fill factor of 86.35%, resulting in a power conversion efficiency exceeding 22%. The improved performance is attributed to favorable energy band alignment and enhanced charge transport, which together facilitate efficient carrier extraction and reduce recombination losses. In addition, the device demonstrates a high quantum efficiency of approximately 96% within the 200-733 nm wavelength range. These findings highlight the promise of lead-free perovskite solar cells in delivering high performance while offering a more sustainable and environmentally friendly alternative to traditional lead-based technologies.
The morphological regularity, thickness uniformity, and size controllability of two-dimensional materials play a crucial role in regulating their physicochemical properties. However, achieving a synergistic balance among these three factors remains a key challenge in the field. In this study, through a systematic investigation of 36 salt-assisted growth systems, we discovered that CsCl promotes the lateral growth of SnS2, while KI optimizes the crystal morphology. Using a CsCl/KI mixed salt system, we successfully grew triangular, ultrathin, large-area SnS2 nanosheets with a size exceeding 200 & micro;m and a thickness of only 1.8 nm. Angle-resolved polarized Raman spectroscopy (ARPRS) revealed that SnS2 nanosheets transferred onto SiO2 substrates exhibit intrinsic in-plane isotropy. In contrast, SnS2 nanosheets grown directly on mica substrates display a 90 degrees periodic variation in Raman peak intensity with polarization angle, indicating significant in-plane anisotropy. This anisotropy arises from interfacial stress induced by lattice mismatch between the mica substrate and SnS2, which breaks the intrinsic symmetry of the material. In addition, the transition of SnS2 nanosheets from in-plane optical isotropy to anisotropy were confirmed by the polarized optical microscopy characterization. These results demonstrate that the mixed salt-assisted growth strategy provides a new approach for synergistically controlling the size, shape and thickness of two-dimensional materials and offers a novel method for inducing anisotropic property in intrinsically isotropic two-dimensional materials through lattice mismatch.
Warburg impedance models the process of diffusion of mobile ions from the electrode to the diffusion layer under a sinusoidal voltage applied at one polarity of an electrochemical cell, and the diffusion of mobile ions to the electrode at the other polarity. As a result, the process does not go beyond the diffusion layer. In this case, the diffusion of Tl+1 ions in the T lI nS2 crystal (as well as in solid solutions) after 25 Mrad irradiation is considered to be responsible for the formation of the Warburg diffusion impedance. The transition to the superionic state is confirmed by measuring the temperature dependence of electrical conductivity. It was found that the relaxation time decreases after the crystals are exposed to radiation. The complex plane diagrams were analyzed using the equivalent circuit substitution method. It has been shown that the system of solid solutions undergoes a phase transition to the superionic state after gamma-irradiation.
