Silver Paste Research Articles

Three-dimensionally printable hollow silica nanoparticles for subambient passive cooling

Abstract Solar reflectance and thermal emissivity are critical benchmarks for evaluating the effectiveness of passive cooling strategies. The integration of three-dimensional (3D) printing techniques with passive cooling materials enables local thermal management of multifaceted objects, offering opportunities for unexplored energy-saving applications. For example, conformal printing of cooling materials can mitigate solar absorption caused by the top metal electrodes in solar cells, thereby improving their efficiency and lifetime. In this study, we report the synthesis of 3D printable hollow silica nanoparticles (HSNPs) designed to induce subambient cooling performance under daylight conditions. HSNPs with diameters of 400–700 nm and silica shell thicknesses of approximately 100 nm were synthesized using an in-situ sol–gel emulsion method. Subsequently, these HSNPs were formulated into printable pastes by carefully selecting the mixture concentration and molecular weight of polyvinylpyrrolidone (PVP). The PVP-linked HSNPs exhibited a solar (0.3–2.5 μm) reflectivity of 0.98 and a thermal (8–13 μm) emissivity of 0.93. In contrast to a single silica nanoparticle (NP), the scattering analysis of a single HSNP revealed a distinctive scattering distribution characterized by amplified backward scattering and suppressed forward scattering. In outdoor daytime experiments, the HSNP-printed sample led to the subambient cooling of a dielectric substrate, surpassing the cooling performance of reference materials such as silica NPs, silver pastes, and commercial white plastics and paints.

Enhancing Electrical and Physical Contacts of Copper‐Electroplated Silicon Heterojunction Solar Cells through Chemical Pretreated Seed Layers

Copper electroplating offering the potential to replace low‐temperature sintered silver pastes holds significant promise as a metallization process for silicon heterojunction (SHJ) solar cells (SCs). To unlock the full potential of copper electroplating, it is crucial to enhance the contact properties between the electroplated grids and the indium tin oxide (ITO) films, addressing both contact resistivity and physical adhesion. Herein, a zinc‐assisted Fe2+ system to modify the ITO film is used, leading to the formation of an In/Sn/SnO mixed‐metal transition layer. This transition layer serves as a seed layer for metal electroplating, reducing contact resistivity and enhancing the mechanical connection between the electroplated metals and the ITO films. Following the ITO pretreatment process, the contact resistivity is significantly reduced from 1.4 to 0.2 mΩ cm2, and the peel force value of the pretreated sample reaches 14.2 N mm−1, which is 75.3% higher than that of the untreated sample. The proof‐of‐concept SHJ SC with copper electroplating after ITO pretreatment achieves a remarkable power conversion efficiency of 22.6%. These results clearly demonstrate that ITO pretreatment using the zinc‐assisted Fe2+ system is an effective approach for enhancing contact properties and improving the performance of copper‐electroplated SHJ SCs, showcasing significant potential for industry applications.

Effect of Silver Powder Microstructure on the Performance of Silver Powder and Front-Side Solar Silver Paste.

Silver powder, as the primary component of solar silver paste, significantly influences various aspects of the paste's performance, including printing, sintering, and conductivity. This study reveals that, beyond the shape and size of the silver powders, their microstructure is a critical factor influencing the performance of both silver powders and silver pastes in solar cell applications. The growth process leads to the formation of either polycrystalline aggregated silver powder or crystal growth silver powder. Analyzing the performance characteristics of these different microstructures provides guidance for selecting silver powders for silver pastes at different sintering temperatures. Polycrystalline aggregated silver powder exhibits higher sintering activity, with a sintering initiation temperature around 450 °C. The resulting silver paste, sintered at 750 °C, demonstrates a low sheet resistance of 2.92 mΩ/sq and high adhesion of 2.13 N. This silver powder is suitable for formulating silver pastes with lower sintering temperatures. The solar cell electrode grid lines have a high aspect ratio of 0.37, showing poor uniformity. However, due to the high sintering activity of the silver powder, the glass layer dissolves and deposits more silver, resulting in excellent conductivity, a low contact resistance of the silver electrode, a low series resistance of the solar cell of 1.23 mΩ, and a high photoelectric conversion efficiency of 23.16%. Crystal growth silver powder exhibits the highest tap density of 5.52 g/cm3. The corresponding silver paste shows improved densification upon sintering, especially at 840 °C, yielding a sheet resistance of 2.56 mΩ/sq and adhesion of 3.05 N. This silver powder is suitable for formulating silver pastes with higher sintering temperatures. The solar cell electrode grid lines are uniform with the highest aspect ratio of 0.40, resulting in a smaller shading area, a high fill factor of 81.59%, and a slightly higher photoelectric conversion efficiency of 23.17% compared to the polycrystalline aggregated silver powder.

Enhanced performance of PFO-ZnO nanorods nanocomposite photodiodes grown on ZnO NRs/ZnO/ITO-coated glass

An improved photodiode was fabricated using a nanocomposite of poly (9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) and zinc oxide nanorods (ZnO NRs). The nanocomposite was prepared by scratching hydrothermally grown ZnO NRs on a glass substrate into the prepared PFO solution. The nanocomposite layer was deposited using the spin-coating method and silver (Ag) paste was applied as the electrode. The resulting photodiode configuration is Ag/PEDOT:PSS/PFO-ZnO NR/ZnO NRs/ZnO/ITO. Ultraviolet–visible (UV–Vis) spectroscopy showed a slight blue shift and a slight increase in the optical bandgap. The nanocomposite-based photodiode showed improved performance, due to increased active surface area for the separation of photogenerated electron-hole pairs between PFO and ZnO and also because of the higher current density of ZnO. Finite-Difference Time-Domain (FDTD) simulations showed ZnO NRs increased electric field strength and exciton generation rate throughout the PFO polymer in the nanocomposite. The photodiode with the nanocomposite showed the best performance at −5 V bias voltage under 385 nm illumination, obtaining responsivity of 1.45 A W−1, Detectivity of 2.19 x 1010 Jones, and External quantum efficiency (EQE %) of 468 %.

Effect of lead-free glass on the current transmission method at the Ag/Si interface in crystalline silicon solar cells.

Environmental protection mandates have spurred the widespread adoption of lead-free glass in electronic material adhesion. Glass powder, crucial for solar silver paste, notably affects the ohmic contact at the Ag-Si interface of crystalline silicon solar cells. This study examines how TeO2 content influences the high-temperature flowability and wettability of lead-free Bi2O3-TeO2-based glass powder, alongside the interplay between the glass's thermal properties and interface contact. Additionally, it investigates the Bi2O3-TeO2 ratio's impact on current transmission through the interfacial glass layer. Experimental results show that the synthesized glass powder exhibits superior high-temperature flowability and wettability, with a low contact resistance of 1.5 mΩ cm2 in silver paste applications. This study also proposes an optimal approach for enhancing current transmission through the interfacial glass layer. Consequently, this glass powder is highly valuable for c-Si solar cell silver paste applications, offering novel insights into improving current transmission efficiency.

Development of Silver Paste With High Sintering Driving Force for Reliable Packaging of Power Electronics

Development of Silver Paste With High Sintering Driving Force for Reliable Packaging of Power Electronics

Aging tests of mini-modules with copper-plated heterojunction solar cells and pattern-transfer-printing of copper paste

Abstract: Mini-module aging tests with differently interconnected heterojunction solar cells having industrially viable copper metallization are presented. The plating process comprises 3 steps: firstly, screen printing of a seed-grid layout using a copper-based paste, followed by deposition of a dielectric layer over the entire wafer surface, and finally, selective copper electrodeposition on grid positions. Modules with Smartwire interconnection, fabricated with M6 half-cells, are stable in extended TC and PID tests. DH degradation is at 5% after 2700 h (glass-glass modules without edge sealing). Shingle modules, realized in collaboration with CEA INES and AMAT, exhibit notably higher fill factor compared to reference modules with screen-printed silver paste. This improvement is attributed to the superior line conductivity achieved with plated copper. TC stability of shingle modules is very good, whereas after 2000 h damp-heat aging more than 2% loss in fill factor is observed. Using pattern-transfer-printing technology narrow, high aspect-ratio lines have been obtained: with a seed-grid of pure copper paste, reinforced with electrodeposited copper. Line dimensions and line resistance as well as first cell results are presented.

Synthesize and Characterization of Crystalline Structure and Phase Transition Temperature of Ce Substituted Ba- TiO3 Ceramics

Characterization and synthesize of Ba1-xCexTiO3 (x=0.01mol.) annealed at three different temperatures (1100oC, 1200 oC, 1300 oC) have been studied. For preparing powder of (x = 0.01 moles), Sol- Gel synthesis was carried out according to the stoichiometric conditions. The powder obtained palletized at 1.5 ton /mm2 pressure into a 10 mm dia. Pellet using PVA (polyvinyl alcohol) as binder. The pellets were then annealed at 1100oC for 1 hour. Then silver paste was applied on pellet by fully coating the one side and applying a single dot on other side, for making the pellet as capacitor. The XRD pattern reveals that the lattice parameter increases with the Ce doping and c/a ratio decreased which shows that tetragonality decreases. In all investigated samples it is assumed that the phase transition analysis, after doping Ce in BaTiO3 the Curie temperature decreases.

Monolithic Self-Charging Storage Device with Stable 3 V Operation

Monolithic self-charging storage device with Stable 3 V Operation The energy paradigm has been changing from the traditional power plant system to micro-gride system based on renewable energy. However, renewable energy including wind, solar, and vibration, is intermittent and influenced by time, weather, and location. Thus, the suitable storage device is required for efficient utilization of renewable energy. The representative combination of renewable energy and energy storage device is an energy storage system (EES) consisting of photovoltaic systems and Lithium-ion batteries. The EES is mainly applied to social infrastructure system that generate large amounts of energy. As the Fourth Industrial Revolution progresses, the rechargeable power supply including Lithium-ion batteries is widely applied to wireless system such as sensor network, wearable device, and electric vehicles. However, the batteries have only storage function, so periodic charging is required. Thus, it is necessary to develop technologies for portable and small energy generation/storage as standalone power sources that can continuously supply power to various electronic devices. Large-scale energy production/storage system has entered the maturity stage, but the development of portable and small energy generation/storage systems based on IoT is in its early stages. To date, research on this system is conducted by simply connecting energy harvesting and energy storage device to external wires after manufacturing them independently. However, the introduction of additional wires is complicated in system design and manufacturing and has difficulty in miniaturization. These problems have motivated the integration of both functions into one device. The integrated device is fabricated by sharing one electrode, called a common electrode between the energy harvesting and storage components. Currently, research on a monolithic photo-charging storage device that integrates solar cells and energy storage devices into one device has been developed. This structure can miniaturization and flexible design, thereby it is suitable for the wearable and smart device. Although the importance of an integrated device is emphasized, the current research of monolithic device is limited to the fabrication of an integrated device without considering their practicability. In other words, most studies focus on simply connecting two devices to achieve the highest overall efficiency. In this case, since the open circuit voltage of single solar cell is under 1 V, the operation of photo-charging storage device is limited to 1 V. Thus, we proposed the monolithic photo-charging storage device operating at 3 V. We fabricated the multiple series-connected perovskite solar cell to increase the operating voltage. Since the secondary batteries are difficult to be charged by the high current density of 20 mA cm−2 solar cell owing to their storage mechanism, we choose the supercapacitor with the rapid response to an applied electric field change. We select the silver paste as the common electrode owing to its strong adhesion, high electric conductivity, and lack of chemical/mechanical damage to the solar cell and supercapacitor. Based on density functional theory (DFT) calculation, we prove the common electrode exhibits good compatibility with our supercapacitor and solar cell. For this reason, the proposed photo-charging storage device exhibits an ultra-fast charging time of less than 3 sec under AM 1.5 G illumination and high overall efficiency of 13.17 % at 1 mA cm−2 and 9.87 % at 20 mA cm−2. For electric double layer supercapacitors integrated with a solar cell, higher discharging current densities that 20 mA cm−2 have not been reported so far. We firstly demonstrate the behavior of photo-charging storage device under light/dark state by the impedance analysis. By the impedance analysis, we demonstrated that the solar cell provides a stable power supply to the supercapacitor under light condition. Further, the additional encapsulation ensures the long-term stability of photo-charging storage device and demonstrate the indoor cycling performance. We prove the photo-charging storage device has high potential as an IoT sensor power source. Figure 1

Formation of Sn seeds on indium-free TCO for plating metallization of silicon heterojunction solar cells

The cost-prohibitive ITO and low-temperature silver paste pose significant challenges in the manufacture of SHJ solar cells. The SnO2-based TCO (indium-free) and Cu electroplating are promising solutions to address these issues. The key point of Cu electroplating is the seed layer for achieving good adhesion and low contact resistivity to the TCO. In this study, we report the electrochemical reduction method for the Sn seeds on FTO films, offering an alternative to the costly vacuum deposition process. We reveal that the electrochemical reduction process is dominated by the breaking of lower-energy bonds during electrons injection, resulting in the formation of tin nanoparticles which serve as the excellent seeds for the subsequent electroplating of a nickel metal layer on the FTO film. A tightly binding interface without any pores between the FTO film and Ni was observed, confirming its effectiveness. Our calculation results using the DFT method manifest that the binding energies of Sn/Ni interface are significantly lower than SnO2/Ni, indicating that Sn seeds present a lower energy barrier for deposition, which promotes Ni deposition kinetics. The integration of indium-free TCO, seeds preparation of electrochemical reduction, and copper electroplating is expected to boost SHJ solar cells in near future.

Characteristic of graphene-based thick film gas sensor for ethanol and acetone vapor detection at room temperature

<p>Ethanol and acetone are volatile organic compound gases widely used in food processing. Health problems such as irritation of the eyes, nose, and throat can affect human health if exposed to these gases. Two graphene gas sensors were fabricated using a screen-printing technique onto a glass substrate to compare their performance to the acetone and ethanol vapors at room temperature. The graphene paste was prepared by mixing 95 wt.% of the binder with 5 wt.% of graphene nanoflakes. A silver paste was used asthe interdigitated electrode of the gas sensor and becamethe first layer of the gas sensor. The silver paste was deposited on the glass substrate using a screen-printing technique and fired at 150°C for 15 minutes. Next, the graphene paste was depositedonto the interdigitated electrode using a screen-printing technique and becamethe second layer of the gas sensor. The graphene was annealed at 200°C for 30 minutes. Both graphene gas sensors responded well to ethanol and acetone vapor with an n-typed gas sensor at room temperature. As a comparison, the graphene gas sensor showed better characteristics in terms of response and recovery characteristicsto ethanol vapor than acetone vapor at room temperature. The response and response time of the graphene-based thick film gas sensor to ethanol were approximately 21.89 and 24.08, respectively.</p>

Screen printable copper pastes for silicon solar cells

The current work demonstrates the successful metallization of a PERC silicon solar cell with screen-printable copper (Cu) paste that is sintered at elevated temperature in air atmosphere. The existing state of the art in Silicon (Si) solar cell metallization is silver (Ag) paste; Cu cost is 1/100th the cost of Ag and has a comparable conductivity. However, Cu undergoes rapid oxidation at elevated temperatures and the high diffusion of Cu into Si restricts its usage in the metallization of silicon solar cells. In this paper, a Cu paste containing a proprietary mixture of antioxidant additives and diffusion inhibitors was used to make front gridlines on PERC cells. The Cu-printed cells were fired in an IR belt furnace with a peak temperature of 576 °C in air atmosphere. The solar cells discussed here reached an efficiency of 19%, which is 88% of the efficiency measured for a commercial Ag-printed cell. The working devices were further characterized using STEM, EDX, ToF-SIMS and long-term suns-Voc studies demonstrating an absence of Cu diffusion. Furthermore, thermally stressing the Cu-printed solar cells yielded a reduction of less than 1.9% of the initial pseudo fill factor (pFF) after 1000 h at 200 °C. The shunt resistance of cells monitored over 3 years remained within 2.5% of its initial value, which demonstrates the effectiveness of the Cu diffusion barrier.

Preparation of Superfine Spherical Silver Powders for Solar Cell Silver Paste via Non-wetting Effect of the Liquid/Solid Interface

Preparation of Superfine Spherical Silver Powders for Solar Cell Silver Paste via Non-wetting Effect of the Liquid/Solid Interface

Electrochemically Functionalized Single-Walled Carbon Nanotubes With Polypyrrole for the Detection of Sub-Part-per-Million Concentrations of Ammonia

Here we report a facile method of functionalization of single-walled carbon nanotubes (SWNTs) with polypyrrole and making a chemiresistive sensor using the functionalized nanomaterial for sub-part-per-million detection of ammonia gas at room temperature. The sensor fabrication involves three steps: (i) immobilization of SWNTs by dip coating method on a silane-treated silicon/silicon dioxide substrate, (ii) printing of two parallel lines of conducting silver paste 5 mm apart as source and drain to define the source and the drain electrode, and (iii) in-situ electrochemical polymerization to functionalize the SWNTs with polypyrrole. The functionalization of SWNT was confirmed using electrochemical current-voltage measurements. The functionalized SWNTs exhibited several folds higher sensitivity to ammonia gas than the pristine SWNTs. A charge density of 0.85 C.cm−2 was optimum for electrochemical functionalization, providing maximum sensing response toward ammonia. The functionalized SWNTs showed a large measurable response starting from 50 to 750 part-per-billion (ppb) of ammonia with a sensitivity of ∼1.55% per ppb, and a limit of detection of 5 ppb of ammonia. Almost complete recovery of the sensor and an average response time of ∼9 min was also observed.

Structure and properties of low-melting Bi2O3-B2O3-MnO-CuO glasses for conductive silver paste

Structure and properties of low-melting Bi2O3-B2O3-MnO-CuO glasses for conductive silver paste

A Study on the Effect of Various Initiators of Acrylic Binder for Low-Temperature Curing Silver Paste

A Study on the Effect of Various Initiators of Acrylic Binder for Low-Temperature Curing Silver Paste

Improvement of solder interconnections applied on back contact solar cells with low-temperature copper paste busbars

This work addresses the solderability and the reliability of n-type IBC ZEBRA cells with screen printed copper paste busbars. Improvement of the solderability by Sn60Pb40 solder alloy coated PV ribbon using an industrial automated IR stringer is reported. For qualification of the module reliability, climate chamber thermal cycling (TC) and damp heat tests (DH) were performed on mini modules with variations in material combinations: low temperature silver and copper pastes, each of them demanding dedicated soldering process parameters and two different encapsulation materials: polyolefin elastomers (POE) and ethylene vinyl acetate (EVA). All tested modules passed 3 x IEC TC and 2 x IEC DH, while the modules with EVA encapsulant passed DH 3000 as well. The copper paste metallized modules with EVA encapsulant showed no degradation in pseudo fill factor (pFF) and open circuit voltage (VOC), proving the statement that no copper diffuses into the silicon bulk.

Improvement of the structural, dielectric, ferroelectric, and piezoelectric of PbZr0.52Ti0.48O3 nanopowder features for ultrasonic applications

Smart ferroelectric lead zirconate titanate (PbZr0.52Ti0.48O3) was synthesized in the morphotropic phase boundary by a sol-gel auto-combustion strategy. The as-prepared powder was calcined at three different temperatures, 700, 800, and 900 °C for 3 h, each. The tetragonality of the final product increases with the rise of calcination temperature. Thermal gravimetric analysis and differential thermal gravimetric analysis depicted that complete crystallization of PZT was observed at 400 °C. Structural, vibrational, and microstructure studies were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy investigated for grains and elemental analyses and high-resolution transmission electron microscopy (HR-TEM). Results of XRD and HR-TEM were compatible, showing the formation of nanocrystalline powder with coexisting tetragonal and rhombohedral phases. Rietveld refinement of XRD data was carried out using material analysis using diffraction software in order to obtain the lattice constants. For mechanical and electrical measurements, disks were pressed at 10 MPa. The samples were burned out at 500 °C for 1 h and then 1100 °C for 2 h to obtain more dense disks. The surfaces of the disks were coated with silver paste, followed by burning out for almost an hour. Dielectric and piezoelectric characteristics for the fabricated PZT samples were determined in detail. From these analytical techniques and collected data, one can deduce that the sample annealed at 900 °C can be used as an ultrasonic transducer in various metrological applications.

Prediction of Electrical Resistance with Conductive Sewing Patterns by Combining Artificial Neural Networks and Multiple Linear Regressions.

This study aims to estimate the impact of sewing thread patterns on changes in the resistance of conductive yarns coated with silver paste. Firstly, the structure of the conductive yarns was examined, and various variations in the length and angle of individual sewing stitches were observed and analyzed through experiments. The results revealed that as the length of an individual stitch decreased, the width of the conductive yarn increased. Additionally, variations in the stitch angle resulted in different resistance values in the conductive yarn. These findings provide essential information for optimizing sewing patterns and designing components. Secondly, the comparison between models using multiple linear regression analysis and sewing neural networks was included to show optimized resistance prediction. The multiple linear regression analysis indicated that the stitch length and angle were significant variables affecting the resistance of the conductive thread. The artificial neural network model results can be valuable for optimizing sewing patterns and controlling resistance in various applications that utilize conductive thread. In addition, understanding the resistance variation in conductive thread according to sewing patterns and using optimized models to enhance component performance provides opportunities for innovation and progress. This research is necessary for the textile industry and materials engineering fields and holds high potential for practical applications in industrial settings.

Fine conductive line printing of high viscosity CuO ink using near field electrospinning (NFES)

Modern printed electronics applications require patterning of fine conductive lines of sufficient thickness. However, the two requirements for pattern width and thickness are a trade-off. To print fine pattern at a micrometer size, the nozzle diameter must be approximately the size of the pattern width, so only low-viscosity inks are used. As a result, the pattern is likely to be very thin and multiple overlapping printing is required for sufficient conductance. In order to use high viscosity ink for fine patterning, near field electrospinning (NFES) is attracting attention because it can print very thin and thick patterns using large nozzles (high-viscosity ink). Until now, silver paste ink has been used for microconductive patterning using electrospinning. However, Ag nanoparticle (NP) inks are expensive. In this study, we report the use of a relatively inexpensive CuO NP ink for electrospinning-based printing. For implementation, the material preparation, printing and post-processing process are discussed. For post-processing, a continuous wave (CW) green laser with a 532 nm wavelength was used to reduce the CuO to Cu and sinter the nanoparticles. After sintering, the 50 μm width and 1.48 μm thick Cu conductive line exhibited a resistivity of 5.46 μΩ·cm, which is 3.25 times of the bulk resistivity of Cu.