Ag Si Research Articles

Effect of Te-based glass on contact formation and electrical properties in Si solar cells

Numerous studies have focused on applying Te-based glass in crystalline Si solar cells due to their low thermal properties and high chemical resistance. However, the correlation between Te-based glass and contact formation in these solar cells has not been addressed. In this study, we investigated the relationship between the thermal properties of glass frits and the content of the TeO2/(TeO2+PbO) ratio under fast firing. Subsequently, the effect of the contact formation on the electrical characteristics of Si solar cells with Te-based glass frits in Ag paste was observed. The thermal properties of the glass frits and the contact formation between the Ag electrodes and Si wafer were observed. The results showed that the morphology of the interfacial structure significantly affected the electrical properties. The thickness of the glass layer was proportional to the series resistance of the Si solar cells. The lower viscosity of the glass frits was due to the formation of a higher amount of recrystallites on the n+ emitter and the penetration depth of the recrystallites into Si, which resulted in a higher efficiency. It was apparent that the contact formation between the Ag electrodes and the Si wafer was caused by the fused glass frits in Ag paste under fast firing.

Rare-earth element doping in glass frit for improved performance in silicon solar cells

Glass frit plays an important role in the silver paste for silicon solar cells. In this work, we prepare glass frit doped with different rare-earth elements (Y, La, Sm, Er) and study how the doping element affects the performance of the solar cells. Solar cells with La-doped and Sm-doped glass frits show average conversion efficiencies higher than 17.5%, while solar cells with Y-doped or Er-doped frit show lower efficiencies. By analyzing the Raman spectra of the rare-earth doped glass frits, we find that the average coordination number of Te–O ([Formula: see text]) in the glass can be tuned by the rare-earth dopant. La or Sm doping leads to a moderate value of [Formula: see text], which is believed to achieve a glass formation ability that optimizes the structure of the Ag–Si interface of the cell for the best performance.

Obtaining Composite Nanoparticles via Electron Beam Irradiation and Modeling the Processes of their Formation by Means of Molecular Dynamics

The partial pressure of vapors of silicon and such metals as silver, copper, and tantalum is estimated and Ag–Si and Ta–Si systems are modeled thermodynamically. Nanoparticles of two types (core–shell and Janus-like) are obtained experimentally via high-temperature gas-phase synthesis using a direct-action electron accelerator. Characteristic features of the formation of composite nanoparticle structures are revealed by means of molecular dynamics, based on modified embedded-atom potentials.

Resonant-frequency properties of low-dimensional junction of semiconductor-metal-semiconductor and calculation methodology

The article describes frequency characteristics of semiconductor–metal–semiconductor Si–Ag–Si structures (ohmic contacts) having metal nanolayers as well as features of resonance phenomenon and sandwich structure energy interaction. Mathematical simulation of mentioned above processes is provided. The limiting factor for resonance process is determined. It is found that the resonance frequency is a subject of semiconductor-metal junction parameters while metal layer thickness impact is minor.

Metal Nanoparticle-Decorated Silicon Nanowire Arrays on Silicon Substrate and their Applications.

Herein, we report an efficient method to produce silver (Ag) nanoparticle-decorated silicon (Si) nanowire (NW) arrays on a pyramidal Si (P-Si) substrate by using a pure chemical method and rapid thermal annealing in different atmospheres. A metal-assisted chemical etching technique was used to produce vertical Si NW arrays on pyramidal Si. The etching was observed to be heavily dependent on the substrate type. On planar Si (100), the etching was observed to occur in a uniform manner. However, the etching rate was observed to increase from the top to the base of the Si pyramid. The Si NWs produced from P-Si have zig-zag sidewalls as observed from high-resolution transmission electron microscopy images. However, for the same oxidant concentration, Si NWs produced from planar Si (100) consist of straight and amorphous sidewalls. Local variation of oxidant concentration is responsible for the formation of different sidewalls. The substrates are both surface-enhanced Raman scattering (SERS) active and hydrophobic. The hydrophobicity is due to the dual scale of roughness contributed to by both pyramidal and NW structures. Finite-difference time-domain simulation shows that the gap between two Ag spheres and also the gap between Si NWs and Ag spheres contributed to SERS enhancement.

Effect of Ag addition on the precipitation evolution and interfacial segregation for Al–Mg–Si alloy

The effect of Ag addition on the precipitation evolution and interfacial segregation for Al–Mg–Si alloys was systematically investigated by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), atom probe tomography (APT) and density functional theory (DFT) calculation. At the early aging stage, Ag atoms could enter clusters and refine the distribution of these clusters. Then, Ag atoms preferentially segregate at the GP zone/α-Al and β"/α-Al interfaces at the peak aging stage by the replacement of Al atoms in FCC matrix. With prolonging aging time, Ag atoms generally incorporate into the interior of β" precipitate, facilitating the formation of QP lattice (a hexagonal network of Si atomic columns) and the local symmetry substructures, Ag sub-unit (1) and Ag sub-unit (2). At the over-aged stage, the Ag sub-unit (1) and Ag sub-unit (2) could transform to the β′Ag (i.e. β′Ag1 and β′Ag2.) and Q′Ag unit cells, respectively. All the precipitates at the over-aging stage have a composite and disordered structure due to the coexistence of different unit cells (β′Ag1, β′Ag2, Q′Ag and β′) and the non-periodic arrangement of Ag atoms within the precipitate. In the equilibrium stage, the incorporated Ag atoms in the precipitates release into the α-Al matrix as solute atoms or form Ag particles. In general, Ag atoms undergo a process of “segregate at the precipitate/matrix interface → incorporate into the interior of precipitate → release into the α-Al matrix” during the precipitation for Al–Mg–Si–Ag alloys. Besides, Ag segregation is found at the interfaces of almost all metastable phases (including GP zone, β″, β′/β′Ag phase) in Al–Mg–Si–Ag alloys. The Ag segregation at the β′/α-Al interface could increase the length/diameter ratio of β′ phase and thus promote the additional strengthening potential of these alloys. These findings provide a new route for precipitation hardening by promoting the nucleation and morphology evolution of precipitates.

Effect of solute redistribution on twinnability of twins at a crack tip in Al alloys

The twinnability of twins at a crack tip in Al-X (X = Zn, Li, Ge, Mg, Au, Ag Si, Cu, Sc, Sr, Y, Rb, Zr and La) have been investigated within the framework of the generalized planar fault energy curves by using first-principles calculations. It is found that concentration distribution of solute atom is a key factor affecting the twinnability. Solute atoms under Fermi–Dirac distribution would lead to a greater influence in twinnability than uniform distribution. For most Al alloys, twinnability almost keeps stable, which directly explains the rarity of twins produced in Al alloys. It is significant that the twinnabilities of Al-X (X = Sr, Rb and La) increase continuously with the increasing concentration of Sr, Rb and La atoms. Our results indicate that the atomic size effect plays an important role in the change of twinnability, and atoms whose radius is more than 1.3 times of Al would have more obvious effects on twinnability.

Modification of titanium surface via Ag-, Sr- and Si-containing micro-arc calcium phosphate coating

The current research is devoted to the study of the modification of the titanium implants by the micro-arc oxidation with bioactive calcium phosphate coatings containing Ag or Sr and Si elements. The coatings’ microstructure, phase composition, morphology, physicochemical and biological properties were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). Ag-containing and Sr-Si-incorporated coatings were formed in alkaline and acid electrolytes, respectively. The formation of the coatings occurred at different ranges of the applied voltages, which led to the significant difference in the coatings properties. The trace elements Ag, Sr and Si participated intensively in the plasma-chemical reactions of the micro-arc coatings formation. Ag-containing coatings demonstrated strong antibacterial effect against Staphylococcus aureus AТСС 6538-P. MTT in vitro test with 3T3-L1 fibroblasts showed no cytotoxicity appearance on Sr-Si-incorporated coatings.

Design of ultra-high sensitive biosensor to detect E. Coli in water

Escherichia coli (abbreviated as E. coli) are bacteria found in water, in food. The present work focuses applications of surface plasmon resonance (SPR) based biosensors to detect E. coli. SPR is a label-free technology that is used to detect biological samples. The SPR based biosensor design consists of optical wave guide with different structures of metal–dielectric interfaces and effort has been done to optimize design parameters for improved sensitivity. Metal-dielectric structures considered are Au–Si, Ag–Si, Au–GaAs and Ag–GaAs. Obtained simulation results indicates that the performance of the proposed sensor can be enhanced by varying the thickness and material of metal–dielectric interfaces. The device sensitivity obtained 1071.42 nm/RIU by considering metal-dielectric interface of Gold (thickness 0.074 μm) and Gallium Arsenide (thickness 0.22 μm). This result is significantly higher than sensitivity value of 250 nm/RIU found in published literature for similar type of sensor. From the simulation graph it is clear that for small change in refractive index (RI), value of 0.07 (1.33–1.4), there is significant shift in wavelength. This shows that the sensor is highly sensitive towards the change in RI and can be fabricated as lab-on-chip based biosensor. The optimized sensor was tested for detection for E. coli and sensitivity of 400 nm/RIU obtained. The design is compact and easy to fabricate using optical lithography as compared to the conventional optical component based SPR sensor.

Solute clustering and precipitation in an Al–Cu–Mg–Ag–Si model alloy

Solute clustering and precipitation in an Al–Cu–Mg–Ag–Si model alloy has been investigated by atom probe tomography (APT) as well as high-angle annular dark-field (HAADF) imaging and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM). Nine types of solute clusters (Cu, Ag, Mg–Cu, Mg–Ag, Mg–Cu–Si, Mg–Ag–Si, Mg–Ag–Cu, Cu–Ag–Si and MgAgCuSi) were observed by APT in both the as-quenched alloy and after ageing the alloy at 180 °C for 1 h. Three types of precipitates (Ω (AlCuMgAg), θ (Al2Cu) and Mg2Si) were observed by APT and HAADF-STEM after further ageing at 180 °C for 24 h and 100 h. We propose that MgAgCu and MgAgCuSi clusters are likely to be responsible for the formation of the Ω (AlCuMgAg) phase. Furthermore, we also suggest that the θ (Al2Cu) phase forms from Cu clusters and the Mg2Si phase forms from the decomposition of MgAgSi and MgAgCuSi clusters by losing Ag to Ω phase growth. Many early binary clusters (Mg–Cu, Mg–Ag) do not seem to undergo a significant further growth during ageing; these are more likely to be transformed into complex ternary and quaternary clusters and be subsequently consumed during the growth of large clusters/precipitates. Furthermore, it is proposed that the plate-like Ω (AlCuMgAg) precipitates evolve continuously from the MgAgCu and MgAgCuSi clusters, rather than via heterogeneous nucleation on their precursors (i.e. MgAgCu and MgAgCuSi clusters). More interestingly, even after ageing at 180 °C for 100 h, the Ω (AlCuMgAg) precipitates remain coherent with the α-Al matrix, indicating that these precipitates have a high thermal stability. This can mainly be attributed to the presence of a single Mg–Ag-rich monolayer observed at the interface between the Ω precipitate and the α-Al matrix, significantly improving the coarsening resistance of the Ω (AlCuMgAg) precipitates. Our results thus reveal links between a variety of solute clusters and the different types of precipitates in the Al–Cu–Mg–Ag–Si model alloy. Such information can in the future be used to control the precipitation by tailoring solute clustering.

Hybrid Metal-Semiconductor Meta-Surface Based Photo-Electronic Perfect Absorber

Metal films and semiconductor materials have been utilized for numerous optoelectronic devices due to the impressive electrical features. Nevertheless, the feasible way for achieving light anti-reflection or perfect absorption from opaque metal films and high-index semiconductors has not been established yet. In this work, we numerically propose and demonstrate a new functional metal–semiconductor slab, which can produce perfect light absorption in the optical range. High-index semiconductor resonators have been used to provide strong optical field coupling with the incident light. For the Ag–Si resonant slab consisting of a silicon rings array in the Ag slab, dual-band light absorption with the absorption efficiency above 99% is achieved due to the hybridized coupling of photonic and plasmonic modes for the Si and Ag resonators. Additionally, tri-band light absorption can be obtained when a paired silicon rings array is used. Moreover, these absorption properties can be spectrally manipulated via tuning the structural parameters. Furthermore, the absorber scheme is observed to be realizable by other metals and semiconductors. These optical and structural features can not only provide alternative ways for multi-band light absorption but also suggest new insight on the functional optoelectronics such as the infrared photo-detectors, hot-electron excitation, and nonlinear optics.

Farfield Under Small Scattering Angle in the Rectangular Ag–Si–SiO2 Cavity

In this paper, the farfield under small scattering angle was investigated in the rectangular Ag–Si–SiO2 cavity by FDTD. The simulation results showed that Re(E) of the farfield was related to the monitoring wavelength and was a function of monitoring wavelengths. Moreover, in the rectangular Ag–Si–SiO2 cavity, the amplitude of Re(E) changed as the silicon height d varied, and maximum amplitude A of Re(E) could be approximated as the functions of transverse length l and thickness t of silver film under small scattering angle. Re(E) was independent of the transverse length w2 and the longitudinal length d of the cavity in RCM and was also irrelevant with the dielectric constant of silver films. The amplitude A of Re(E) increased as l and t of silver film increased.

Special aspects of the thermodynamics of formation and polarisation of Ag/Si nanoparticles

An analysis of the mechanism of formation of composite nanoparticles of Ag/Si shows that it depends on their stoichiometric composition, conditions of condensation and crystallisation. During the crystallisation of the nanoparticle core, eutectics consisting of silver and silicon layers are formed. Diffraction fringes in the nanoparticle core are caused by the formation of eutectic platelets during crystallisation of phase components. Layers of the conductor Ag and semiconductor Si form, creating an electric charge at the boundaries. We demonstrate the dependence of the sizes of these Ag/Si nanoparticles on the rates of heating and cooling of the materials during synthesis.

Hydrogen Storage, Magnetism and Electrochromism of Silver Doped FAU Zeolite: First-Principles Calculations and Molecular Simulations.

The complex configuration, H2 adsorption binding energy, magnetic, and optical properties of FAU zeolites with Ag cations loaded by ion exchange in the vacant dielectric cavities were investigated by employing the first-principles calculations with all-electron-relativistic numerical atom-orbitals scheme and the Metropolis Monte Carlo molecular simulations. The visible absorption spectrum peaked at distinct wavelengths arranging from red or green to blue colors when changing the net charge load, due to the produced various redox states of Ag cations exchanging at multiple Li+-substituted sites. The spin population analyses indicate the ferrimagnetic coupling between Al–O–Si framework and Ag cations originates from the major ferromagnetic spin polarization in Ag cation cluster coordinating with sodalite cages, with the net spins appreciably depending on the Ag content and exchange site. The H2 adsorption capacities and binding energies represent significant dependence on the content, location, and electronic property of Ag cations introduced into the FAU zeolites. The evident decrease of H2 adsorption binding energy with increased loading concentration demonstrates repulsive interaction between H2 molecules and heterogeneous adsorption configuration on Ag cations. The adsorption sites of H2 sorted by the binding energy with different adsorption configurations were correlated with exchange sites of Ag cations under different Ag loading to comprehend the H2 adsorption mechanism.

Fluoride Fiber Sensor With Huge Performance Enhancement via Optimum Radiative Damping at Ag–Al2O3–Graphene Heterojunction on Silicon

Surface plasmon resonance-based fiber optic sensor with multilayer heterojunction is simulated and analyzed. The constituent materials are ZBLAN fluoride core, NaF clad, amorphous Si layer, Ag layer, Al2O3 interlayer, and graphene monolayer. The main idea behind the study is to optimize the radiative damping ( i.e. , optimum radiative damping, ORD) at the Ag–Al2O3–graphene heterojunction in order to enhance the sensor's figure of merit (FOM) as much as possible. The effect of graphene monolayer's presence on sensor's FOM is also examined. Multiple occurrences of ORD may be achieved by coordinated variation of Ag and Al2O3 layer thicknesses along with light wavelength. Among the several prominent ORD conditions, the combination of 45.3-nm-thick Ag layer, 11-nm-thick Al2O3 layer, and 938.7-nm wavelength leads to a massively large FOM of 31806.65 RIU–1. The above FOM of the FOSPR sensor is nearly six times that for the corresponding prism-based SPR sensor ( i.e. , 5500 RIU–1) reported earlier with Al2O3 interlayer and MoS2 monolayer at λ = 1200 nm. Further, the proposed sensor provides substantially greater FOM compared to existing prism-based and FOSPR sensors.

Femtosecond Laser-Induced, Nanoparticle-Embedded Periodic Surface Structures on Crystalline Silicon for Reproducible and Multi-utility SERS Platforms.

Fabrication of reproducible and versatile surface-enhanced Raman scattering (SERS) substrates is crucial for real-time applications such as explosive detection for human safety and biological imaging for cancer diagnosis. However, it still remains a challenging task, even after several methodologies were developed by various research groups, primarily due to (a) a lack of consistency in detection of a variety of molecules (b) cost-effectiveness of the SERS substrates prepared, and (c) byzantine preparation procedures, etc. Herein, we establish a procedure for preparing reproducible SERS-active substrates comprised of laser-induced nanoparticle-embedded periodic surface structures (LINEPSS) and metallization of silicon (Si) LINEPSS. LINEPSS were fabricated using the technique of femtosecond laser ablation of Si in acetone. The versatile SERS-active substrates were then achieved by two ways, including the drop casting of silver (Ag)/gold (Au) nanoparticles (NPs) on Si LINEPSS and Ag plating on the Si LINEPSS structures. By controlling the LINEPSS grating periodicity, the effect of plasmonic nanoparticles/plasmonic plating on the Si NPs embedded periodic surface structures enormously improved the SPR strength, resulting in the consistent and superior Raman enhancements. The reproducible SERS signals were achieved by detecting the molecules of Methylene Blue (MB), 2,4-dinitrotoluene (DNT), and 5-amino-3-nitro-l,2,4-triazole (ANTA). The SERS signal strength is determined by the grating periodicity, which, in turn, is determined by the input laser fluence. The SERS-active platform with grating periodicity of 130 ± 10 nm and 150 ± 5 nm exhibited strong Raman enhancements of ∼108 for MB and ∼107 for ANTA molecules, respectively, and these platforms are demonstrated to be capable, even for multiple usages.

Sustainable industrial technology for recovery of Al nanocrystals, Si micro-particles and Ag from solar cell wafer production waste

Solar cell wafer industry is classified as one of the most complex electronic industries that produces a significant proportion of waste in the form of broken/damaged cells or cells having some defects in their chemical composition that can generally be called Rejected Solar Cell Wafers (RSCWs). Although these wastes contain valuable metals (e.g. Silver (Ag), Aluminum (Al), and Silicon (Si)), unfortunately there is currently no obvious strategy for recovery of these metals and landfilling is considered the primary option for their disposal what can lead to serious soil contamination and human health risks if the waste is not treated properly. This research aims to develop an integrated technology to recover all these metals as high added value nano/micro products with total recovery rate > 98%, thus achieving the sustainability and goals of circular economy. Milling process was used as a pretreatment to break the chemical and mechanical bonds between Ag electrodes, Al electrode, and Si layer of RSCW samples to increase the surface area for reaction. The pretreatment was followed by leaching process using Nitric Acid (HNO3) with concentration > 60% to dissolve Ag and break the chemical bonds between spherical Al microparticles in the Al paste layer. Thus the particles were separated and only a small amount of the Al was dissolved from the surface of the particles since due to the high concentration of HNO3 passivation of Al occurred, forming a thin layer from Aluminum Oxide (Al2O3) that prevented the further dissolution of Al. Under the effect of soundwaves, the separated particles began splitting further and exfoliate into Al nanocrystals. After that, micro-filtration process was used to extract Si microparticles from the leached solution and the extracted particles were purified by etching process using Hydrofluoric acid (HF) to remove Silicon Nitride contamination. Centrifugal process was used to separate Al nanocrystals from the leached solution. Finally, Hydrochloric acid (HCl) was added to the remaining saturated solution to recover AgCl. SEM-EDS, FTIR, ICP, XRD, and TEM were used to analyze and examine the selected wafers and recovered materials. Also, the economic performance, sustainability, and CO2 emissions of the advanced technology were evaluated.

Ti–Zr–Cu–Fe–Sn–Si–Ag–Ta bulk metallic glasses with good corrosion resistance as potential biomaterials

Ti47Cu38−xZr7.5Fe2.5Sn2Si1Ag2Tax (x = 1–4; at%, the same below) bulk metallic glasses (BMGs) with good bio-corrosion resistance and mechanical properties were fabricated by copper mold casting. Critical diameter of the Ti-based BMGs with 1 at%–4 at% Ta was 3 mm. The Ta-incorporated Ti-based BMGs exhibit higher open current potential and parallel passive current density in comparison with those of Ti–6Al–4V alloy in 0.9 wt% NaCl and Hank’s solution, implying their good corrosion resistance. The pitting corrosion potential of the Ti-based BMGs gradually increases up to about 1.25 V with Ta addition increasing up to 4 at% in 0.9 wt% NaCl solution. Among the present Ti-based BMGs, the alloy bearing 2 at% Ta exhibits the optimal integration of mechanical properties, including the compressive fracture strength exceeding 2000 MPa, relative low Young’s modulus of 98 GPa, plastic strain of 3.4% and high hardness of HV 599. The Ta-bearing Ti-based bulk metallic glasses with integration of relative high GFA, good mechanical properties and high bio-corrosion resistance are beneficial for biomedical applications.

Impact of the Presence of Busbars During the Fast Firing Process on Contact Resistances

Uniform and low contact resistances between Ag grids and Si emitters are very important for reducing series resistance losses in screen-printed silicon solar cells. In this paper, we studied systematically the contact resistance of firing-through Ag pastes on samples that were processed in a fast firing furnace with and without the presence of busbars. We fabricated p-type full-area aluminum back surface field and n-type passivated emitter rear totally diffused solar cells with various doping concentrations and surface morphologies. For all tested conditions, lower contact resistances were obtained when firing without busbars. For instance, by omitting the busbars during firing, on a 138 $\Omega$ /sq phosphorus emitter, the median contact resistance dropped from 7.5 to 0.7 m $\Omega$ $\cdot$ cm $^{2}$ , and on an 85 $\Omega$ /sq boron emitter, the median contact resistance decreased from 80 to 1 m $\Omega$ $\cdot$ cm $^{2}$ . Furthermore, we found that the pure Ag paste outperformed the AgAl paste in contacting boron emitters. An explanation of these results might be the short-circuit effect, which is a fundamental mechanism that strongly influences contact formation. In addition, in spite of the significant impact of the presence of busbars during firing on contact resistances, its impact on the $J_{0,\text{met}}$ was found to be only marginal.

Effect of basicity of glass frits on electrical properties of Si solar cells

The purpose of this study is to understand the effects of the basicity parameter of glass frits added to the front contact of three-busbar Si solar cells on the removal of the anti-reflective coating (ARC) and the electrical characteristics of the cell. We investigated PbO-TeO2-SiO2 glass systems by adding oxides to improve the etching of the interface between the Ag electrode and the Si wafer. The thermal properties and viscous flows of the frits were characterized using differential thermal analysis and a hot-stage microscope. The microstructure of the glass layer at the interface of the Ag electrode and Si wafer was observed using scanning electron microscopy and transmission electron microscopy. The results showed that the electrical properties were dependent on the morphology of the interfacial structure. The addition of oxides to the glass system produced more recrystallites on the n+ emitter with a greater penetration depth in the Si wafer, thereby increasing the efficiency of the solar cell. The reactivity of the glass affected the removal of the ARC and the electrical properties of the Si solar cells were influenced by the charge transport facilitated by the Ag crystallites.