Glass Frit Research Articles

Room temperature wafer bonding through conversion of polysilazane into SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {SiO}_{2}$$\\end{document}

Room temperature wafer bonding is a desirable approach for the packaging and assembly of diverse electronic devices. The formation of SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {SiO}_{2}$$\\end{document} layer at the bonding interface is crucial for a reliable wafer bonding as represented by conventional bonding techniques such as hydrophilic bonding and glass frit bonding. This paper reports a novel concept of room temperature wafer bonding based on the conversion of polysilazane to SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {SiO}_{2}$$\\end{document} at the bonding interface. As polysilazane is converted to SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {SiO}_{2}$$\\end{document} by hydrolysis, in this work, adsorbed water is introduced to the bonding interface by plasma treatment, thereby facilitating the formation of SiO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {SiO}_{2}$$\\end{document} at the wafer bonding interface. The experimental results indicate that the adsorbed water from the plasma treatment diffuses into the polysilazane layer and facilitates its hydrolysis and conversion. The proposed method demonstrates the successful wafer bonding at room temperature with high bond strength without interfacial voids. This technique will provide a new approach of bonding wafers at room temperature for electronics packaging.

Characterization of NTC thick film thermistor paste Cu0.2Ni0.5Zn1.0Mn1.3O4

A powder of Cu0.2Ni0.5Zn1.0 Mn1.3O4 composition for custom thermistor was prepared by using the respective mixture of metal oxides and solid state reaction at 1000 ?C/4h in air. The obtained thermistor powder was milled in the planetary ball mill and agate mill for a prolonged time to achieve submicron powder. The prepared thermistor powder was further characterized by using XRD and SEM techniques. After that, the thermistor powder was pressed into small disc-shaped samples and sintered at 1150?C/2h. The sintered samples were also characterized by using XRD and SEM. The main electrical properties such as nominal resistance R and thermistor exponential factor B were measured in the climatic test chamber. After that, the thick film paste was prepared using the same powder, an organic vehicle and a glass frit. The paste was printed on alumina substrate, dried at 150 =?C /30 min and sintered in air at 850?C /10 min in a hybrid conveyor furnace. Planar electrodes were printed on the sintered NTC thermistor layer using PdAg thick film paste. The electric properties of the sintered thick film thermistor were also measured in the climatic test chamber. The obtained results were used for development of novel self-heating thermistor applications.

Jetting and droplet formation of particle-loaded fluids

Inkjet printing is an attractive method for patterning and fabricating objects across many areas of industry. There is a growing interest in the printing of inks with high particle-loading, such as inks containing glass frit, ceramic and functional inks. However, the use of these inks is often limited due to uncertainty regarding the impact of their rheology on the printing process. Understanding of the role of complex rheology in the jetting of loaded inks is therefore needed to facilitate the wider application of inkjet printing. Here, we characterize the complex rheology and the jetting of model dispersion inks (containing 10, 15, and 23 vol. % TiO2 nanoparticles) and compared them with those without particles. The jetting of the model fluids was conducted with a commercial inkjet printhead (nozzle diameter 34 μm) and visualized with stroboscopic and ultra-high-speed imaging. For low particle concentrations, droplet formation is generally similar to those of unloaded inks, provided their Ohnesorge number and Weber number are matched, although the filament of the loaded model fluid tends to have earlier break-off, having a shorter length. The jetting reliability decreased with increase in particle-loading until reliable jetting can no longer be achieved, due to local particle–particle interactions in the ink channel and in the filament during the fast extensional thinning process. A jetting map is presented which illustrates the influence of particle-loading on the droplet formation, and indicates that the acceptable range of Ohnesorge number for jetting is reduced as the particle-loading is increased.

A new filtration system for extraction and accurate quantification of microplastics.

The analysis of microplastics is crucial due to their widespread occurrence and significant impact as environmental pollutants. Appropriate extraction and analytical techniques are necessary to evaluate the abundance, dispersal, and effects of microplastics. In this context, the filtration step to extract microplastics from solution media is indispensable for quantifying microplastics accurately. Usually, a pretreatment procedure such as density separation or solvent extraction is employed before filtration. Nevertheless, the adsorption of microplastic particles onto the glassware surface is known to occur and careful rinsing is inevitable for a suitable recovery rate. The study presents a novel filtration device developed for easy use to increase microplastic recovery from liquid samples. Fluorescent polyethylene (PE) particles were used to examine recovery by optical microscopy and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The conventional filtration system (CFS) exhibited lower microplastic recovery (45.1 ± 7.9%, n = 10) due to the adsorption of microplastics onto the inner surface and the bottom edge of the upper glass funnel. In contrast, the newly developed modified filtration system (MFS) enables fast suction of liquid samples by removing the glass frit with the upper glass funnel and filter being spatially separated. The significantly improved recovery rates using MFS for PE particles were 100% (n = 5) and 93.4 ± 3.4% (n = 10), respectively, confirming the feasibility of the newly developed filtration system to analyze microplastics using Py-GC/MS. The study highlights the importance of filtration processing in establishing analytical standards for assessing and managing microplastics by suggesting MFS as an advanced filtration system.

Investigation of the Processing Behavior and Stability of Different Glass Frit Materials

Although glass frit bonding has long been a well-established process in the industry, research and development efforts are continuously improving it for application in modern MEMS products. First, it should be mentioned that the main advantage of the glass frit bonding is easily integration of this process module into even the most complex technologies. Using screen printing, the glass frit paste can be applied in a structured manner to one of the two wafers to be bonded, no subsequent structuring (e.g., by lithography and etching) is necessary. Subsequently, the paste is transformed into a compact glass in a batch process (the organic binder is burned out in a furnace and the glass particles are melted). The bonding is performed in conventional wafer bonders. The glass frit, which is located as an intermediate layer between the wafers to be bonded, is melted, and joined by surface wetting to form a heretic seal (vacuum or defined gas pressures can be included). During cooling the glass solidifies and forms a very strong and reliable bond. Virtually all surface layers utilized in microsystems technology can be bonded. The surface roughness of the wafers does not play any role here and even rather high topographies (e.g. metal lines in the bond interface) can be well covered and sealed [1]. Related to this process flow, the glass frit bonding is very cost attractive, e.g., compared to Al-Ge eutectic bonding.The research and development activities of the last years, the requirements that led to them and the corresponding solutions are to be presented and discussed here. Bond frame width: screen printing is mostly associated with very coarse and broad structures and in fact a few years ago, the bond frame width determined the chip size. In the meantime, bond frame widths of 100 µm and smaller can be realized, which is hardly larger than with other bonding processes and allows the economical production of small chips. To realize this, special new screen materials are of key importance. Wafer layout of the Glass Frit layer: with the smaller chips, sealing rings at the wafer edge and support structures in the scribe line, the degree of coverage during screen printing increased significantly, which makes the release of the screen and thus a defined printing process much more challenging. These requirements can be achieved with the new screen materials and measures for keeping the back of the printing screen clean. Glass frit in complex manufacturing chains: Glass frit wafer bonding is not only utilized at the very end of the process to encapsulate MEMS structures; it is now also part of complex wafer level packaging technologies for realizing SoC (system on chip) solutions. After wafer bonding, many different process steps are implemented to create through-silicon-vias (TSVs) and solderable metallizations, for example. The above-mentioned sealing rings at the wafer edge are an important requirement for bonded wafers in such processes, in which mainly wet chemicals are used, therefore it is also essential that the glass frit is chemically resistant and thermally stable up to a certain temperature. This was investigated for different glass frit materials, and it can be concluded that there is a good stability against water and solvents. The resistance to bases varies from material to material and acids usually destroy the glass (Figure 1). Regarding the temperature, it can be stated that up to 50 °C below the bonding temperature, the Glass frit can be considered as solid. Lead-free glass frit materials: until now, lead in glass frit materials was exempt from the legal regulations governing their use. These exemptions will expire in the foreseeable future [2]. Therefore, the detailed evaluation of lead-free glass frits is of very high importance. These materials are currently being investigated in terms of the entire process chain in preparation for industrial application. This evaluation faces some challenges (crystallization tendency of lead-free glasses) but also advantages (e.g., significantly low bonding temperatures are possible with Te-based glass solders). Even though glass frit bonding appears at first glance to be a well-understood process that is easy to apply. There are several modern manufacturing processes, with new challenges that can be mastered by understanding the materials and the processes. However, this requires extensive research and optimization.Literature:[1] Knechtel, Roy. "Glass frit bonding: an universal technology for wafer level encapsulation and packaging." Microsystem technologies 12.1-2 (2005): 63-68.[2] DIRECTIVE 2011/65/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL Figure 1

Study on the deformation during laser-assisted glass frit bonding process

With the development of optoelectronic technology, laser-assisted glass frit bonding has been widely used in the field of bonding. In this study, three types of glass frits, with thicknesses of approximately 3, 8, and 14 μm, were tested. A set of real-time observation systems was built to monitor the deformation of the glass substrates and the behavior of the glass frit during the bonding process. The angular deformation of the glass substrates on the side of the melting area was calculated based on the interference stripes. The temperature field in the bonding process was calculated via simulations. This was verified using thermocouple temperature measurement. During the bonding process, the maximum temperature of the glass frit reached 665 °C and the glass substrates were concaved in the molten area. The bonding width was linearly related to the angular deformation of the glass substrates, and the Pearson correlation coefficient was r = 0.92. When the thickness of the glass frit was approximately 3 and 14 μm, r exceeded the value of 0.98. In the bonding process, larger pores were able to reduce the deformation of the glass substrates. The samples with almost no pores exhibited a larger increase in the deformation.

Improving thermal insulation and fire resistance of ceramifiable EVA/ceramic hybrid composites via low temperature sintering and foaming strategy

Energy efficient buildings, propulsion components and thermal protection systems require materials with high thermal protective properties. Traditional polymer composites or ceramic materials have limited comprehensive applications because of their poor thermal protective properties or poor processability. Herein, a novel fire resistant and thermally insulating polymer/ceramic hybrid ceramifiable composite was developed based on low temperature sintering principle and foaming on fire strategy. Specifically, the influences of raw materials of low temperature ceramics, such as glass frit, phosphate, etc, on the properties of ceramifiable ethylene-vinyl acetate (EVA) composites were investigated. Its fire resistance and thermal insulation properties were evaluated by simulating different sintering environments. The results show that the ceramifiable composite exhibits the highest improvement in fire resistance because a crystalline phase was formed at high temperatures. Gas evolution from the thermal decomposition of ammonium polyphosphate (APP) and EVA contributes to the formation of the porous structure in ceramic residues. The optimal system can resist above 1000 °C flame for 30 min without disintegration, and the temperature of the unfired side was maintained around 200 °C. The reliability of the strategy was verified by the effective medium theory model.

Improving of the luminous efficacy of the YAG:Ce phosphor in glass by doping with the transition metals into the glass frits

Improving of the luminous efficacy of the YAG:Ce phosphor in glass by doping with the transition metals into the glass frits

Fabrication of Jello-Based Ag/AgCl Reference Electrode from Recyclable Resources to Enhance Undergraduate Laboratory Student Experience and its Promising Utilization in Corrosion and Electrochemical Sensing

This paper presents a realistic approach to experience electrochemical principles in the context of an upper undergraduate research course where students will learn how to fabricate and calibrate a reference electrode (RE) which is an essential component of an electrochemical system. Among many commercially available REs, Ag/AgCl RE is one of the most employed REs in teaching laboratories and research. However, the REs fabrication and assembly pose technological challenges in addition to their cost especially for large quantities procurement for undergraduate laboratories. To circumvent these constraints, one alternative is to fabricate them in the lab, however, the use of harmful chemicals and complicated techniques limits their practical fabrication in teaching laboratories. Therefore, this study, devised a simple and cost-effective method for fabricating a homemade Ag/AgCl RE assembly where jello is used instead of a glass frit (referred as JRE) from recyclable and obsolete items available in common undergraduate laboratories. The as-fabricated jello RE exhibited excellent sensitivity and accuracy as compared to a commercially available BASi RE from the cyclic voltammetric (CV) studies. Subsequently, JRE showed its potential in two distinct electrochemical experiments, including potentiodynamic Tafel corrosion scans and electrochemical sensing and detection of Ascorbic Acid (AA). In addition to outstanding reproducibility, JRE demonstrated higher stability even after four months of storage in the refrigerator. Keywords: Undergraduate laboratories, Homemade reference electrode, recyclable wastes, corrosion, electrochemical detection

Development of the composition of matte glaze with usage of pharmaceutical glass waste for the production of porcelain stoneware

The paper shows the prospects of using pharmaceutical glass waste for partial replacement of high-value frits in the glazes composition. According to the results of X-ray fluorescence spectroscopy, the glass wastes belong to the group of alkali-containing aluminoborosilicate glasses. The results of thermomicroscopic and dilatometry studies showed that the combination of industrial waste frits and glass waste allows obtaining coatings that, according to their technological characteristics, meet the conditions of porcelain stoneware high-speed firing. The conditions for the resource-valued glass waste use as part of porcelain stoneware tiles glazes have been established. This allowed to use their potential as efficiently as possible and to partially replace (within 15–30%) high-value frits. Combinations of waste glass and industrial boron-free frits with high crystallization ability due to the increased content of alkaline earth oxides (RO=22–34 wt.%) were studied to prepare opaque matte coatings. Glazes compositions have been developed, which under conditions of high-speed firing, form matte coatings due to the directed crystallization of phase’s complex (ZnAl2O4, Zn2SiO4 and CaAl2Si2O8). Ceramic granite with white color coating (brightness coefficient of 80–83%) that differs by "silky" mattness (mirror reflection coefficient of 31–42%), high heat resistance (10 or more heat changes) and abrasion resistance of III–IV class was obtained. The best results were observed when using matte glazes in a complex with engobe, which includes the same glass waste in the amount of up to 30 wt.%. This is in general ensures a high level of their utilization, a significant high-value raw materials saving and an energy costs reduction for fritting.

Investigation of the Processing Behavior and Stability of Different Glass Frit Materials

Glass frit wafer bonding is a widely used process in the development and production of microsystems, especially for integrating sensors and their signal conditioning circuits. As a result, glass frit bonded wafers must withstand subsequent process modules, such as silicon (wafer) through vias (TSVs) processing. The properties of glass materials for wafer bonding play a crucial role in ensuring the performance and reliability of such wafers. With the advent of new environmental regulations, Lead-free glass frit materials are being developed to replace the current Lead-containing glasses. In this context, four different glass frit materials were investigated and compared in detail, and the bonding behaviors of these materials were analyzed. It was found that the low-melting main components of these glasses determined their properties and performance. The glasses' electrical and chemical properties were also investigated, and their impact on the bonding process was analyzed. The results of this study provide guidance for the process integration of glass frit wafer bonding and open up new possibilities. In addition, the study highlights the need for practical evaluations for specific applications and related details.

Investigation of Spark Plasma Sintering on Microstructure-Properties of Zirconia Reinforced Fluormica Glass for Dental Restorations.

Conventional sintering methods of dental ceramics have limitations of high temperature and slow cooling rates with requirements of additional heat treatment for crystallization. Spark plasma sintering (SPS) is an emerging technique that has the potential to process dental restorations with dense microstructures and tailor-made clinically relevant properties with optimized processing parameters. This study explored the potential of the SPS of zirconia-reinforced fluormica glass (FM) for dental restorative materials. FM glass frit was obtained through the melt-quench technique (44.5 SiO2-16.7 Al2O3-9.5 K2O-14.5 MgO-8.5 B2O3-6.3 F (wt.%)). The glass frit was ball-milled with 20 wt.% of 3 mol% yttria-stabilized zirconia (FMZ) for enhanced fracture toughness. The mixtures were SPS sintered at a pressure of 50 MPa and a heating rate of 100 °C/min for 5 min with an increase in temperature from 650-750 °C-850 °C-950 °C. Phase analysis was carried out using XRD and microstructural characterization with SEM. Micro-hardness, nano-indentation, porosity, density, indentation fracture toughness, and genotoxicity were assessed. The increase in the SPS temperature of FMZ influenced its microstructure and resulted in reduced porosity, improved density, and optimal mechanical properties with the absence of genotoxicity on human gingival fibroblast cells.

Toward the Development of an Electromechanical Ion-Specific Conveyer Belt

Bromide (Br−) is ubiquitous both in natural waters and those impacted by anthropogenic activities, such as, the discharge of treated or untreated wastewaters, releases from coal-fired power plants and hydraulic fracturing operations, and sea water intrusion. The development of methods for the extraction and purification of Br−, particularly from Br− -rich brines, is regarded as of great economic interest owed to the uses of bromine in many industrial processes. In fact, the removal of Br- from drinking water is beneficial from a public health perspective, as it can lead to the formation of regulated disinfection byproducts (DBPs) during water treatment. Although various alternatives have recently been proposed to remove halide anions, such as bromide, from drinking water, none of them have proven sufficiently effective for large-scale application (see e.g. Ref. 1).The present contribution describes a strategy for the removal and purification of bromide from an aqueous solution containing chloride in amounts that closely mimic those found in natural brine sources. As will be described, this tactic relies on the selective electrosorption of Br− on Au, an inert metal electrode material from such a synthetic brine, and its subsequent desorption into a second aqueous solution devoid of Br−.The all glass multi compartment cell employed for these experiments ‘shown schematically in the figure above consists of a central cylindrical cup filled with 0.01 HClO4 supporting electrolyte, which houses the reference, RE, and counter electrodes connected on either side to two identical cups of smaller diameter, C1 and C2 are separated from the central cup by glass frits so that diffusion between C1 and C2 is negligible. At the start of a regular experiment, C1 is filled with a solution containing 28 mM KCl and 12.5 mM KBr, the synthetic brine, in the supporting electrolyte, and C2 is filled with only supporting electrolyte. In the initial stage of this protocol, a gold foil is immersed in C1, which together with the RE and CE would form a conventional 3-electrode cell and a potential of 1.3 V vs RHE is then applied to the Au foil using a potentiostat to induce anion adsorption for ca.10 s. which is sufficient for Br-(aq) and Cl-(aq) to achieve their equilibrium coverages under the specific conditions of the experiment, as represented by the blue arrow. Based on the results of independent optical measurements, Br-(aq) would be the predominant ion adsorbed on the Au surface at this high potential. Subsequently, the Au foil is emersed from the solution without disconnecting the potentiostat, immersed into C2, and a potential of 0.2 V applied, which is just positive of the onset of hydrogen evolution but negative enough for adsorbed Br- to fully desorb, as represented by the red arrow. This process is then repeated tens of times, at the end of which the composition of the solution in C2 is analyzed using the methylene blue (MB) spectroscopic method described by Uraisin, et al. (2) to determine specifically Br-(aq), and a slightly modified Mohr’s turbidimetry technique, which employs K2CrO4 as the indicator, to determine the total amount of Br-(aq) and Cl-(aq).Four independent runs involving 50 to 75 sequential transfers were performed in order to assess the efficiency of this process, and found to yield an increase in the Br-(aq) concentration from an initial 30% in C1, up to higher than 75% in C2. Overall, the efficiency of this process can be increased by a corresponding increase in the area of the electrode. Alternatively, one can envision a continuous process involving a segmented electrode in the form of a belt and appropriate potential controls, that would be continuously emersed and immersed into C1 and C2, acting as a virtual ionic conveyer. Various aspects of this unique technology and its prospects for large scale implementation will be discussed. Acknowledgements This work was supported by a grant from NSF, CHE-1412060 References Sanchez-Polo, J. Rivera-Utrilla, E. Sahli, U. von Gunten, Ag-Doped Carbon Aerogels For Removing Halide Ions In Water Treatment, Water Res., 41, 2007,1031-1037Uraisin, T. Takayanagi, M. Oshima, D. Nacapricha, S. Motomizu, Kinetic-Spectrophotometric Method For The Determination Of Trace Amounts Of Bromide In Seawater, Talanta, 68, 2006, 951-956 Figure 1

Screen printable fire through nickel contacts for silicon solar cells

Metallization of crystalline silicon (Si) solar cells is indispensable for reducing the cost while increasing the overall efficiency. Developing alternative materials to the most commonly used screen printed silver (Ag) contacts is a critical factor. Here, in this study, a nickel (Ni) metal paste consisting of Ni metal particles, glass frit and an organic vehicle is fabricated for screen printed Ni contacts. To prevent possible Schottky barrier formation, a graphene layer is placed on the front surface of the Si solar cell between Ni and Si forming a metal-2D-semiconductor structure ensuring the ohmic (or ohmic-like) contacts. It is demonstrated here that the graphene is transferred successfully onto the textured front surface of the cells and G/2D peaks are observed clearly, indicating the good quality of the graphene layer. Constituents of Ni metal paste, glass frit and organic vehicle, are fabricated in concordance with nickel metal powder and mixed to achieve optimal electrical output parameters. The findings suggest that the transition temperature of the glass frit is between 270 °C and 300 °C resulting in around 475 °C softening temperature, which gives excellent etching behavior to the paste. The average contact resistance of the screen printed Ni contacts governed by etching process is measured around 6.9 mΩ cm2. The SEM images of the contacts show a uniform distribution and sintering behavior similar to that of silver counterparts. The light current-voltage measurements read the open circuit voltage of 660 mV, the short circuit density of 39.11 mA/cm2 and the fill factor of 81.4% resulting in around 21% efficiency.

Fundamental microscopic studies on the etching behavior of silver pastes on poly-Si/SiOx passivating contacts

Screen printing of Ag paste is a key process for implementing polycrystalline-silicon/silicon oxide (poly-Si/SiOx) passivating contacts in industrial solar cells. Thereby, the formation of Ag crystallites on the Si surface is crucial for a low-ohmic contact. Recently, it has been observed that Ag crystallites are predominantly formed within the poly-Si layer and stop at the thermal SiOx, thermal interface, causing a cuboidal shape. To avoid a direct contact of the Ag crystallites with the underlying SiOx, thermal/crystalline-Si (c-Si) interface, a multilayer approach with interlayer SiOx, inter between several poly-Si layers is presented. A stack of three 50 nm poly-Si layers achieves highest cell potential. Further, the metallization process parameters are scanned to check when this cuboidal Ag crystallite shape occurs. While different amorphous-silicon (a-Si) deposition techniques show no changes, there are strong indications that the glass frit etching is responsible for a different etching mechanism causing the breakdown of the SiOx stop.

Construction of efficient silicon solar cells through polymetallic oxidation-reduction triggered by thermite reaction

Optimal metal-semiconductor contact interface is crucial for semiconductor devices, particularly for silicon solar cells aluminum-silicon contact is a key to improve the efficiency of the cell. In this work, a new type of Sb2O3-MoO3-B2O3 glass frits that can trigger a thermite reaction was utilized to improve the Al-Si interface. The low melting temperatures of these glass frits enhance the effect of thermite reaction by providing solid-liquid contact, which enables gradient distribution of the elements and leads to differences in the valence states of the Al-Si layer at the inner and surface regions. The valence states of Al and Sb at the inner layer are higher than those at the surface, while Mo is the opposite. Metallic Mo with a matched work function can lower the potential barrier, thereby improving hole selectivity and enhancing the potential skip-step. As a result, the fabricated solar cell achieved a high open-circuit voltage, a high short-circuit current, and a low series resistance. Consequently, a power conversion efficiency of 19.94% was obtained for a monocrystalline silicon solar cell with full Al-BSF. This work not only presents a new hole-selective contact for silicon solar cells, but also introduces a new approach for regulating the distribution and valence states of interface elements for enhanced efficiency.

Glass microspargers as effective frit spargers in single use bioreactors.

For multiple-use bench scale and larger bioreactors, sintered stainless steel frit spargers are commonly used as microspargers. For bench-scale single-use bioreactors (SUBs), existing microspargers are sintered plastics, such as polyethylene. However, though plastics are readily sterilized by irradiation making them convenient for single use, these designs overlook surface energy properties of the materials of construction. For these sintered plastic spargers, forces at the water-air-surface interface cause bubble coalescence, leading to lower effective mass transfer, higher gas flow rates, and differing pCO2 profiles in cell culture. Alternative materials of construction were evaluated based on contact angle information and bubble formation observations. Sintered glass was chosen over thermoplastic polymers for higher surface wettability as described in the glass/water contact angle, its history as a commonly sintered material, and availability at costs suitable for single use applications. Glass sintered spargers and traditional stainless steel frit spargers were compared by porosity, bubble size, and kL a studies. Mass transfer (kL a) and cell culture performance equal or greater than a standard 20 μm stainless steel microsparger mass transfer efficiency was achieved by a glass frit sparger, of international porosity standard "P40" according to ISO 4793-80, which corresponds to a range of 16-40 μm.

Differently shaped Ag crystallites and four current transport paths at sintered Ag/Si interface of crystalline silicon solar cells

The comprehensive understanding of the Ohmic contact mechanism on the front metalization is highly desirable for further improvement of crystalline silicon solar cells performance. However, there are still controversial views about current transport paths between silver electrode and silicon emitter. To clarify this significant issue, we applied the selective acid etching (AE) process and the method of mechanical stripping process to prepare proper samples for direct observation of the Ag/Si contact interface. It is revealed that four kinds of Ag crystallites are grown with variant shapes and sizes on the pyramid tips, {111} planes, edges and tiny bumps at valleys of the textured Si surface resulting from anisotropic etching of Si emitter by the flowing molten glass frit during firing and the consequent epitaxially growth of Ag on the etching pits during cooling. All these Ag crystallites are in direct contact with Si emitter, serving as the most important contact points on the Si side. Meanwhile, three kinds of spherical Ag particles are formed in the resolidified glass frit during cooling which are crucial tunneling paths, conducting between glass-covered Ag crystallites on silicon and Ag bulk above. As a whole, four current transport paths are suggested mainly via Ag crystallites, Ag particles or both. In addition, the four electron transport paths are further confirmed by the Kelvin probe force microscopy characterization. The clarification and detailed understanding of all current transport paths are key points to design better silver paste and sintering process, and hence to improve the solar cell performance.

Orange-red-emitting (Sr,Ba)3SiO5:Eu2+ phosphor-in-glass film for enhanced color rendering of laser lighting

Nitride red-emitting materials exhibit severe luminance saturation and are thus not suitable for achieving enhanced color rendering in laser lighting applications. The silicate luminescent material (Sr,Ba)3SiO5:Eu2+ displays excellent stability and can emit orange-red light when excited by blue laser light, making it a promising candidate for realizing high-performance laser lighting. In this study, (Sr,Ba)3SiO5:Eu2+ phosphor-in-glass (PiG) films were prepared on a sapphire substrate, and the influences of preparation temperature, mass ratio of phosphor to glass frit (PtG ratio), and film thickness on the application performance of PiG film were analyzed. The (Sr,Ba)3SiO5:Eu2+ PiG film with a PtG ratio of 1:1 and a film thickness of ∼50 μm prepared at 475 °C exhibited optimal comprehensive luminescence performance. This film exhibited a luminous saturation threshold of 5.98 W/mm2, a maximum luminous flux of 372.3 lm, and a luminous efficiency of 62.3 lm/W at the luminous saturation threshold. The maximum luminous flux of the (Sr,Ba)3SiO5:Eu2+ PiG film was 77.6% higher than that of the CaAlSiN3:Eu2+ nitride PiG film. Finally, through the incorporation of green-emitting YAGG:Ce3+ phosphor into the (Sr,Ba)3SiO5:Eu2+ PiG film, laser-driven white light with a luminous flux of 531.7 lm and a high color rendering index (CRI) of 83.4 was realized.

Utilization of waste glass with natural pozzolan in the production of self-glazed glass-ceramic materials

Abstract Significant self-glazed glass-ceramic was obtained from a natural pozzolan and external glass cullet. Natural pozzolan with/without glass cullet was fused to glass melt that quenched in water to glass frits. The dried glass frits were pulverized (<0.083 mm) and then shaped in a stainless mold. The thermal behavior of the glasses shows a widening of the crystallization temperature with the incorporation of the glass cullet between ∼800 and 950°C. Sintering of the shaped glass powder at 1,050°C/2 h lead to the crystallization of augite, enstatite, cristobalite, and hematite. The microcrystalline structure shows massive texture with pores in-between; however, at high magnification regular euhedral to subhedral crystals in submicron to nearly submicron size was developed in the glassy matrix and their microanalysis indicates the dominant augite. The density of the glass-ceramic samples decreases from 2,706 to 2,539 kg/m3 with the incorporation of glass wastes. The sample surfaces show, through force electron microscopy, the fineness and smoothness of the grains with the incorporation of the glassy portion. The microhardness values were between 6.43 and 6.11 GPa. The coefficient of thermal expansion increased from 32.87 (25–300°C) to 66.89 (25–500°C) × 10−7°C−1. The chemical resistance of samples in water (0.0002–0.0016) is better than in an acidic medium (0.0011–0.0017). These glass-ceramic enjoy good density, hardness, and thermal expansion and can be used in the ceramic industry and cladding walls and floors.