Standard Screen Printing Research Articles

Investigation the Influence of Calcination Temperature on Structural, Electrical and Gas Sensing Properties MnO<sub>2</sub> Thick Films

Metal oxide nanoparticles are widely used in various fields, including catalysis, sensing, energy storage, and more. Manganese dioxide (MnO2) is a promising material for gas sensors due to its sensitivity to various gases, including oxidizing and reducing gases. The calcination temperature affects their size, crystallinity, surface area, and other properties. In the present research work, the influence of calcination temperature on the structural, electrical and gas sensing properties of MnO2 nanoparticles or nanopowders was investigated. The MnO2 nanopowder was calcinated at 200, 400, 600, and 800 °C in a muffle furnace for 4 hours. After that, using the calcinated powder of MnO2, the thick films were prepared using the standard screen printing technique. The structural characterizations were investigated using SEM, EDS, and XRD. It has been found that as the calcination temperature is increased, the electrical, structural, and gas-sensing properties of MnO2 change. The prepared thick films calcinated at 200, 400, 600, and 800 °C are labeled as samples 1, 2, 3, and 4, respectively, in this paper. It has been found that sample 4 shows maximum resistivity, a more specific surface area, a smaller crystallite, and a maximum gas response to H2S gas. The maximum sensitivity was found to be 76.32% to H2S gas at operating temperature 120 °C. The response and recovery time was also found quickly.

A Dual-Wavelength Phosphorescent Anti-Counterfeiting Copolymer Containing Eu(III) and Tb(III).

The anti-counterfeiting technology of banknotes, bills and negotiable securities is constantly copied, and it is urgent to upgrade its anti-counterfeiting technology. In view of the defect of easy replication of single-wavelength anti-counterfeiting technology, the bonded copolymer PMEuTb was synthesized, employing the technique of first coordination and then polymerization. The molecular structure of copolymer PMEuTb was confirmed by infrared spectrum and UV-vis absorption spectrum. The internal mechanism of negative correlation between initiator concentration and number-average molecular weight Mn of the copolymer was revealed, and the positive correlation between Mn and luminescent behavior of the copolymer was analyzed. The luminescent properties of copolymer PMEuTb with initiator amount of 0.1% were investigated, the copolymer PMEuTb exhibits dual-wavelength emission of green light and red light under the excitation of ultraviolet light at 254 nm and 365 nm. The copolymer has the lifetime of 1.083 ms at 5D4-7F5 transition and 0.665 ms at 5D0-7F2 transition, which belongs to phosphorescent emitting materials. The copolymer remains stable at 240 °C, and variable temperature photoluminescent spectra demonstrate the luminescent intensity remains 85% at 333 K, meeting the requirements of room temperature phosphorescent anti-counterfeiting materials. The luminescent patterns made by standard screen printing display the green and cuticolor logo at 254 nm and 365 nm, respectively, indicating that the bonded phosphors PMEuTb has potential application in phosphorescent anti-counterfeiting.

QRsens: Dual-purpose quick response code with built-in colorimetric sensors

QRsens represents a family of Quick Response (QR) sensing codes for in-situ air analysis with a customized smartphone application to simultaneously read the QR code and the colorimetric sensors. Five colorimetric sensors (temperature, relative humidity (RH), and three gas sensors (CO2, NH3 and H2S)) were designed with the aim of proposing two end-use applications for ambient analysis, i.e., enclosed spaces monitoring, and smart packaging. Both QR code and colorimetric sensing inks were deposited by standard screen printing on white paper. To ensure minimal ambient light dependence of QRsens during the real-time analysis, the smartphone application was programmed for an effective colour correction procedure based on black and white references for three standard illumination temperatures (3000, 4000 and 5000 K). Depending on the type of sensor being analysed, this integration achieved a reduction of ∼71 – 87% of QRsens's dependence on the light temperature. After the illumination colour correction, colorimetric gas sensors exhibited a detection range of 0.7–4.1%, 0.7–7.5 ppm, and 0.13–0.7 ppm for CO2, NH3 and H2S, respectively. In summary, the study presents an affordable built-in multi-sensing platform in the form of QRsens for in-situ monitoring with potential in different types of ambient air analysis applications.

Exploration of Spectroscopic Study of Screen-Printed Tungsten Oxide: Tin Oxide Nano-Composite Powder Fired at High Temperature

Abstract: Thick films of pure Tin oxide (SnO2) and composite 1%, 3%, 5%, 7% and 9 % tungsten oxide (WO3) incorporated into pure Tin oxide (SnO2) were prepared with standard screen printing technique. All samples were prepared on glass substrate and subjected to drying and firing at 5000C at 5 hours in muffle furnace. Thick films of tin oxide (SnO2) and composite 1%, 3%, 5%, 7% and 9 % Tungsten Oxide (WO3) incorporated into pure tin oxide (SnO2) were examined for Scanning Electron Microscopy (S.E.M), Energy Dispersive X-ray Analysis (E.D.A.X), X-ray diffraction (X.R.D), Fourier Transform infra-Red (F.T.I.R) and Ultra-Violet-visible spectroscopy (U.V) to investigate surface morphology, elemental analysis, crystalline Phases of films, vibrational and spectroscopic study respectively. The spectrophotometric parameters such as absorbance and absorption coefficient were also a part of investigation. The UV-visible spectrophotometric study was encountered in terms of absorbance and absorption coefficient along with varying percentage composition.

Formation of a copper contact grid on the surface of silicon heterojunction solar cells

A comparative analysis of various methods of forming a copper (Cu) contact grid on the surface of silicon heterojunction solar cells (SHJ SC) as an alternative to the standard screen printing method using expensive silver-containing (Ag) pastes is presented. It has been shown that the use of inkjet printing for the formation of protective dielectric masks based on an organic polymer and thin buffer metal layers for the growth of a Cu contact grid by electroplating makes it possible to form a contact grid of the required shape and having sufficient adhesion to the surface of SHJ SC. Using this method, double-sided SHJ SC (size 157x157 mm2) with Cu contact mesh were fabricated, demonstrating an efficiency of 22.9% and an adhesion level of 3-5 N/mm compared to 22.6% and 1.5-2 N/mm using a similar contact mesh based on Ag paste. Keywords: solar energy, monocrystalline silicon, heterojunction solar cell, copper contact grid, electroplating, screen and inkjet printing.

Формирование медной контактной сетки на поверхности кремниевых гетероструктурных фотоэлектрических преобразователей

A comparative analysis of various methods of forming a copper (Cu) contact grid on the surface of silicon heterojunction solar cells (SHJ SC) as an alternative to the standard screen printing method using expensive silver-containing (Ag) pastes is presented. It has been shown that the use of inkjet printing for the formation of protective dielectric masks based on an organic polymer and thin buffer metal layers for the growth of a Cu contact grid by electroplating makes it possible to form a contact grid of the required shape and having sufficient adhesion to the surface of SHJ SC. Using this method, double-sided SHJ SC (size 157x157 mm2) with Cu contact mesh were fabricated, demonstrating an efficiency of 22.9% and an adhesion level of 3–5 N/mm compared to 22.6% and 1.5–2 N/mm using a similar contact mesh based on Ag paste.

Toward 3D‐Printed Electronics: Inkjet‐Printed Vertical Metal Wire Interconnects and Screen‐Printed Batteries

Inkjet and screen printing technologies are well known in the graphic arts industry for the reproduction of texts, images, and graphics. During the last decades, these printing technologies have been attracting increasing interest for the deposition of functional materials, e.g., in the field of printed electronics and for biological applications. However, their usage is mainly limited to 2D applications, i.e., rather flat deposits ranging from nanometers to several tens of micrometers in thickness. For 3D applications, sophisticated additive manufacturing technologies are developed to manufacture structures with high shape complexities. Herein, the potential of standard inkjet and screen printing technology as tools for the development of functional 3D objects is demonstrated. 3D functional structures printed by inkjet and screen printing technology combining conductive and nonconductive materials to a multi‐material structure are shown. A metal nanoparticle ink formulation is applied to inkjet‐print conductive metal pillars with a high aspect ratio (in the range of 50) used as vertical interconnects. The interconnects are encapsulated with an inkjet‐printed polymeric ink formulation and finally used as conductive tracks to light up a solid‐state light‐emitting diode (LED). Screen printing is applied to print primary batteries used as the power source for the LED.

Fluidized Bed Production of Surface Functionalized Powders for Solid Oxide Fuel Cell Cathodes

Surface functionalized powders were produced using the novel technique of fluidized bed chemical vapor deposition. Test structures of SOFC cathodes were fabricated from coated and uncoated powder samples, using standard screen printing and sintering techniques. Electrochemical impedance spectroscopy showed the surface functionalized powers to outperform uncoated cathode powder, in all cases, in the temperature range of 600 C to 800 C. Fluidized bed chemical vapor deposition is shown to be an effective and economical process for production of high performance SOFC cathode materials.

Heterojunction solar cells based on single-crystal silicon with an inkjet-printed contact grid

Results on the creation of a current-collecting grid for heterojunction silicon solar cells by ink-jet printing are presented. Characteristics of the obtained solar cells are compared with those of the samples obtained using standard screen printing.

Effect of Firing Temperature on Electrical and Structural Characteristics of Screen Printed In2O3 Thick Films

In2O3 thick films were prepared on porous alumina (Al2O3) substrate by using standard screen printing technique and fired at different temperatures from 750ºC to 950ºC in air atmosphere. The DC resistance of film was measured by half bridge method in air atmosphere at different temperatures. The films were showing decrease in resistance with increase in temperature indicating semiconductor behavior. The resistivity (ρ), activation energy (∆E) and temperature coefficient of resistance (TCR) are evaluated at different firing temperatures. Samples were characterized by Xray diffraction (XRD) technique, scanning electron Microscopy (SEM)), Energy Dispersive Spectroscopy (EDX) and Atomic force microscopy (AFM) technique, for compositional, phase confirmation and surface growth and morphology study.

Metallization of Si heterojunction solar cells by nanosecond laser ablation and Ni-Cu plating

A key step in industrialization of photovoltaics (PV) is the development of low-cost and large-area metallization processes to substitute the standard screen-printing process of silver paste. Thus Cu and Ni metallization processes enabled by laser patterning have been widely pursued in passivated-emitter rear-cell (PERC) technology. However, the undesirable opto-thermal side-effects of laser processing have so far hindered using similar processes for metallization of Si heterojunction (SHJ) solar cells due to the relatively high sensitivity of SHJ cells to thermal shocks. Here an innovative process is described, in which the laser damage to the SHJ cell is minimized by using a double-mask layer that optically and thermally isolates the device from the laser beam. As a proof of concept, Si heterojunction solar cells of 235cm2 surface area are metallized using this method and >19% power conversion efficiencies are achieved. This process is applicable to any temperature-sensitive electronic device with front conductive surface, such as perovskite/Si multi-junction and semi-transparent perovskite solar cells.

Microwave Characterization of a Thick Film System for Hybrid Packaging Applications

Abstract Thick film material systems for hybrid applications have existed for many years and have provided the ability to create high density interconnects in industries such as consumer, military, telecommunications and automotive electronic devices. Despite their breadth of applications, thick film hybrid circuits are rarely utilized for microwave/millimeter-wave packaging applications. In this work, the DuPont™ QM44 thick film dielectric is characterized up to 40 GHz. Test samples to characterize this thick film system consisted of the screen-printed QM44 multilayer dielectric and QG150 gold thick film conductor and vias on top of a 96% alumina substrate. Three different fabrication methods were used in the fabrication of the test samples to illustrate the effect of processing techniques on material loss properties, with the conductor lines formed through standard screen printing, chemical etching, and laser ablation. Laser ablation is a technique recently utilized to form transmission line features in low temperature cofired ceramic (LTCC) circuits [1] to increase dimensional precision when compared to standard screen printing. S-parameter measurements of microstrip transmission lines demonstrate a system loss at 30 GHz of approximately 0.8 dB/cm for chemical etching, 0.9 dB/cm for laser ablation, and 1.0 dB/cm for screen printing. Through careful design and good processing, acceptable microwave performance of the QM44 thick film system can be achieved up to 40 GHz.

Dispensing Technology on the Route to an Industrial Metallization Process

Abstract This study presents a new developed, inline applicable dispensing platform that is equipped with an advanced version of previously introduced parallel dispensing print heads and works as drop-in-replacement in existing manufacturing lines. At process speeds of up to 700 mm•s-1 and a substantially improved process stability, the impact of the resulting contact geometries on optical and ohmic losses was analysed in detail. A reduced finger width as well as an effective width of just 48% after encapsulation of the finger width leads to nearly 50% reduction of shading losses compared to screen printed samples. A substantially improved finger homogeneity leads to similar grid resistances at 20% less silver consumption. Consequently, recent cell results on industrial emitters (R sh = 90 Ω/sq.) showed an efficiency increase of up to +0.4%abs. in comparison to standard single screen printing reaching top values of η = 20.5% on PERC structures. A key improvement of the technology is the new ability to process certain metal pastes originally designed for screen printing applications and thus keep in track with fast emerging paste development. Successfully evaluated screen printing pastes then can be rheologically adapted in order to reach ultrafine contact fingers at high aspect ratios and extract the whole advantage of this non-contacting printing technology.

Humidity sensing properties of WO3 thick film resistor prepared by screen printing technique

Thick films of tungsten oxide based were prepared using standard screen printing technique. To study the effect of temperature on the thick films were fired at different temperature for 30min in air atmosphere. The WO3 thick films were characterized with X-ray diffraction, scanning electron microscopy and EDAX for elemental analysis. The formation of mixed phases of the film together with majority of monoclinic phase was observed. IR spectra confirm the peak at 1643cm−1 clearly shows stretching vibrations attributed to the WOH bending vibration mode of the adsorbed water molecules. The absorption peaks in the range 879–650cm−1 are attributed to the stretching WOW bonds (i.e. ν [WOinterW]). The peak located at 983cm−1 belong to WO terminal of cluster boundaries. A change in the resistance was observed with respect to the relative humidity when the WO3 thick films were exposed to a wide humidity range of 20–100%. An increasing firing temperature of WO3 film increases with the sensitivity. The parameters such as sensitivity and hysteresis of the WO3 film sensors have been evaluated.

Three Dimensional Microstructural Characterization of Cathode Degradation in SOFCs Using Focused Ion Beam and SEM

The limited durability of solid oxide fuel cells (SOFCs) in practical applications has impeded the commercial adoption of these devices. A primary component of this degradation occurs within the cathode upon long-term exposure to various contaminants, including H2O, CO2, and Cr vapor. These contaminants cause significant microstructural and compositional changes within the cathode that adversely affect activation, polarization mechanisms, and ionic and electronic conductivities. Previous works (Gostovic et al. and Smith et al.) have demonstrated that a number of quantifiable microstructural characteristics can be directly related to SOFC performance, the most important of these being triple phase boundary length (LTPB) and pore surface area. These parameters have not been examined during cell degradation, and further analysis under these conditions will provide insight into specific cell degradation mechanisms, informing future fabrication and operation criteria.In this work, we present a three-dimensional quantification of porous SOFC cathode materials that have been aged in both clean and contaminated atmospheres. Symmetric cathode cells were produced by standard screen printing methods using an yttria-stabilized zirconia (Y2O3-ZrO2, YSZ) electrolyte, and a composite cathode. The composite cathode consisted of 50% lanthanum strontium manganite (La1−xSrxMnO3, LSM) and 50% YSZ by weight. We report here the quantification of and differences between three YSZ/LSM-YSZ symmetric cells: unaged, aged for 480 hours in a clean air environment, and aged for 480 hours under H2O atmosphere. This quantification was performed using a dual-beam focused ion beam/scanning electron microscope (FIB/SEM) to serially mill 30nm slices of the cell, taking an image after each slice. In this way, a series of 2D images was acquired, aligned, and reconstructed into a fully quantifiable 3D volume rendering of the cell near the cathode/electrolyte interface, as shown in Figure 1.After developing a 3D model for each cell, the volumes were quantified by a number of parameters, including LTPB, particle/pore size and distribution, surface area coverage, porosity, phase volume fraction, and tortuosity. Additional information relating to phase connectivity was calculated by generating a “skeleton” network for each phase, and was compared for each cell. The microstructure was then related to cell performance data acquired from the same samples. Furthermore, the detailed microstructure, compositional changes, and the formation of impurity phases due to the contaminants was characterized by transmission electron microscopy (TEM), utilizing both energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS).1. Gostovic, D., Vito, N. J., O’Hara, K. A., Jones, K. S., & Wachsman, E. D. J. Am. Cer. Soc., 94(2), 620–627, (2011).2. Smith, J. R., Chen, A., Gostovic, D., Hickey, D., Kundinger, D. P., Duncan, K. L., & Wachsman, E. D. (2009). Solid State Ionics, 180(1), 90–98. Figure 1: Serial 2D slices of YSZ electrolyte (left) and composite LSM-YSZ cathode (right) acquired in FIB/SEM (a) are reconstructed into a representative 3D volume surface model (b) for further quantification. Data is from unaged symmetric cathode button cell.

On the generation of bulk microdefects in phosphorus-diffused monocrystalline silicon solar wafers after a high-thermal treatment studied by X-ray topography

Oxygen is the most important impurity in free dislocation Czochralski silicon single crystals incorporated interstitially during the growth. The knowledge of oxygen behavior after thermal processes is of great technological importance, since different kinds of bulk microdefects such us SiO2 precipitates, dislocation loops and stacking faults can be generated. In monocrystalline silicon solar cell manufacturing fabrication, there are several high-thermal treatments. The first is the diffusion process at 850–900 °C. Three different kinds of phosphorus diffusion wafers, standard PO3Cl liquid, spray-on and screen printing, were comparatively studied by X-ray topography showing that phosphorus diffusion improves the crystal quality by a gettering process whose best efficiency is in PO3Cl-diffused wafers. Later, another fabrication high-thermal step is for instance the rear surface passivation taking place at temperatures from 800 to 1,050 °C. For this reason, it is important to study how a high-thermal treatment at 1,000 °C affects the different phosphorus-diffused wafers mentioned above. To evaluate and characterize the possible defects induced by the oxygen precipitation, X-ray topography has been employed. Results show that annealed wafers are not perfect crystals; the oxygen precipitation induces the generation of bulk microdefects whose kind, size and density depend on the diffusion method employed. In PO3Cl and spray-on diffused wafers, retardation in the oxygen precipitation process takes place after annealing, while in screen printing this process is recovered and a kind of mixed defects between dislocation loops and platelet precipitates is generated.

21.8% Efficient n-type Solar Cells with Industrially Feasible Plated Metallization

Using plated contacts, many of the challenges of metallizing high-efficiency n-type solar cells can be overcome. Very low resistivity contacts on boron emitters are hard to achieve by standard screen printing, and voltage reductions of up to 30mV with currently available printing paste generations have been reported. In contrast, fully plated contacts have many similarities with evaporated contacts, which so far allow the highest efficiencies shown. Using plated contacts, excellent efficiencies of up to 21.74% are demonstrated in this work, contacting boron emitters with surface doping concentrations as low as 6x1018 cm-3 without significant series resistance losses. Open circuit voltages close to 680mV show that the detrimental effect as observed for screen printed contacts can be avoided. High adhesive forces >2N/mm have been achieved for the contacts by the controlled formation of nickel silicide. Simultaneously, very low series resistance was realized (FF of 81.2%). Plating experiments with 156x156 mm2 n-type solar cells in industrial inline tools yielded satisfactory deposition homogeneity over the cell area for contact fingers and busbars (+/- 2μm deviation), depending on the used ablation method. Fingers were found to systematically plate twice as much as busbars.

Long Term Stability Analysis of Copper Front Side Metallization for Silicon Solar Cells

In this work the development and evaluation of a copper solar cell front side metallization based on a screen printed silver seed layer, a plated nickel diffusion barrier, a plated copper conductive layer and a plated silver capping is presented. Due to a slight adjustment of the standard screen printing process, and subsequent plating of Ni, Cu and Ag, silver consumption was reduced to < 16 mg per cell front side on standard BSF 15.6 cm x 15.6cm mono crystalline wafers, produced only with inline capable techniques. Contact adhesion forces of 1.5 N/mm and, efficiencies of 18.4 % were achieved. For the long term stability analysis on cell and module level, cells with different nickel diffusion barrier masses (10-40mg/cell) were treated on hotplates at 200, 225 and 250°C while detecting degradation due to copper diffusion by measuring the pFF. Sufficient cell life times are predicted for 10 mg Ni by the resulting Arrhenius plot. After 750h damp heat test of one cell modules no visible degradation was determined. This means that accelerated degradation on hotplates show the degradation due to copper diffusion more strongly than 750hours damp heat test. In an additional SEM analysis the plated nickel diffusion barrier showed a closed layer on the fingers and an incomplete layer on the busbars, indicating busbars as possible weak points for copper diffusion due to inhomogeneous Ni plating

Nature and Behaviour of WO3 Thick Film Resistors Properties When Subjected to Firing Temperature

WO3-based thick film resistors were prepared by using standard screen printing technique. This paper was aimed at studying the nature and behaviour due to effect of firing temperature on resistors fired in the range 500-700 0 C in air atmosphere. The material characterization was performed by XRD, SEM, and EDAX for elemental analysis. A mixture of monoclinic, triclinic and hexagonal WO3 was observed in the range 500-7000C. The UV-visible spectra show WO3 exhibits a shoulder at 230 nm along with an ill-defined band at 260 nm. The maximum optical band gap energy of 4.85 eV was calculated at room temperature. The D.C. resistance of the films was measured by half bridge method in air atmosphere at different temperatures. The films showed decrease in resistance with increase in temperature indicating semiconductor behaviour. The TCR, activation energy and sheet resistivity of films were evaluated at different firing

Low-frequency noise, microplasma, and electroluminescence measurements as faster tools to investigate quality of monocrystalline-silicon solar cells

Two sets of c-Si solar cells varying in front side phosphorus doped emitters were produced by standard screen printing techniques. The first group of samples, 3121, was prepared by a combination of standard washing and a bath with a highly dilute HF before diffusion of n þ -emitter. The second group of samples, 3122, was treated only with standard washing. A comparison of solar cell conversion efficiency and results from a noise spectroscopy, microplasma, and electroluminescence presence are presented. As was already shown in previous publications noise spectral density reflects the quality of solar cells, and thus repre- sents an alternative advanced cell diagnostic tool. Our results confirm this relationship and moreover bring clear evidence for the maximum spec- tral noise voltage density being related to the emitter structure. The best results were reached for the group of solar cells in sample 3122, which was treated only with standard washing. © 2013 Society of Photo-Optical