Screen-printed Cells Research Articles

A Screen-Printed Voltammetric Sensor Modified with Electropolymerized Molecularly Imprinted Polymer (eMIP) to Determine Gallic Acid in Non-Alcoholic and Alcoholic Beverages.

This paper presents a low-cost disposable sensor for gallic acid (GA) detection in non-alcoholic and alcoholic beverages using a screen-printed cell (SPC) whose working electrode (in graphite) is modified with electrosynthesized molecularly imprinted polypyrrole (eMIP). Our preliminary characterization of the electrochemical process shows that gallic acid (GA) undergoes irreversible oxidation at potentials of about +0.3 V. The peak potential is not affected by the presence of the eMIP film and alcohol percentages (ethanol) up to 20%. The GA determination is based on a differential pulse voltammetry (DPV) analysis leveraging its oxidation peak. The calibration data and the figures of merit of the analytical method (LOD, LOQ, and linear range) are calculated. To validate the feasibility of the sensor's application for the dosing of GA in real matrices, some non-alcoholic and alcoholic beverages are analyzed. The results are then compared with those reported in the literature and with the total polyphenol content determined by the Folin-Ciocalteu method. In all cases, the concentrations of GA align with those previously found in the literature for the beverages examined. Notably, the values are consistently lower than the total polyphenol content, demonstrating the sensor's selectivity in discriminating the target molecule from other polyphenols present.

LIFT metallization as an alternative to screen-printing for silicon heterojunction solar cells

The electrical characteristics of solar cells are significantly influenced by the metallization process, making it a crucial step. Screen printing is the standard metallization technique, but there is an increasing interest in the development of methods that allow more versatility, higher process control, and a more efficient use of the expensive metallic pastes used. We focus here on the comparison between the standard screen-printing method, and Light-Induced Forward-Transfer (LIFT), a non-contact, very precise technique, able to transfer volumes down to picolitres. The high flexibility, using free-form designs that do not depend on any mask or physical support, and the efficient use of the metallic paste with almost no waste, are other characteristics that point out LIFT as a very promising alternative. In this paper we include the electric characterization of contacts, and solar silicon heterojunction (SHJ) cells metalized with both techniques. The results show a slightly better efficiency for the screen-printed cells, but good series resistance and fill factor values imply that LIFT is a promising alternative for device metallization.

Ascorbic Acid Sensing by Molecularly Imprinted Electrosynthesized Polymer (e-MIP) on Screen-Printed Electrodes

This paper presents the development of a cheap and rapid electrochemical sensor for ascorbic acid detection. In particular, the graphite ink working electrode of screen-printed cells was covered by a film of elecrosynthesized molecularly imprinted polypyrrole (e-MIP); differential pulse voltammetry (DPV) was the selected method for the analyte detection. The ascorbic acid molecules were successfully entrapped in the polypyrrole film, creating the recognition sites. The best results were obtained after polypyrrole overoxidation and performing the measurements in phosphate buffer solution 0.05 M/KCl 0.1 M at pH 7.5. A comparison with the bare and the not-imprinted polypyrrole-modified electrodes showed that the e-MIP-based sensor had the highest selectivity and reproducibility. The developed method was applied to assess ascorbic acid in farmaceutical products, obtaining values not significantly different from the declared content.

Smart Sensor for Lithium Detection: An Environmental Application

In this work, we propose a potentiometric smart sensor for lithium detection in environmental samples based on a screen-printed cell. The graphite screen-printed electrode (GSPE) was first modified by gold and silver nanoparticles to increase the conductivity, and then by an ion-selective membrane, which was directly deposited onto the nanostructured electrode surface. The potentiometric cell, thanks to its small size, was integrated with a portable instrument connected to a smartphone for decentralized analysis. The developed sensor was used in drop- and microflow-configurations and showed a high sensitivity for lithium with a low detection limit (1.6 µM). It was also applied in the analysis of real samples from the industrial recycling of automotive batteries and complex matrices, such as contaminated soils.

Potentiometric MIP-Modified Screen-Printed Cell for Phenoxy Herbicides Detection.

In this study, a molecularly imprinted polymer (MIP)-based screen-printed cell is developed for detecting phenoxy herbicides using 2-methyl-4-chlorophenoxyacetic acid (MCPA) as the template. MCPA is a phenoxy herbicide widely used since 1945 to control broadleaf weeds via growth regulation, primarily in pasture and cereal crops. The potentiometric cell consists of a silver/silver chloride pseudo-reference electrode and a graphite working electrode coated with a MIP film. The polymeric layer is thermally formed after drop-coating of a pre-polymeric mixture composed of the reagents at the following molar ratio: 1 MCPA: 15 MAA (methacrylic acid): 7 EGDMA (ethylene glycol dimethacrylate). After template removal, the recognition cavities function as the ionophore of a classical ion selective electrode (ISE) membrane. The detected ion is the deprotonated MCPA specie, negatively charged, so the measurements were performed in phosphate buffer at pH 5.5. A linear decrease of the potential with MCPA concentration, ranging from 4 × 10-8 to 1 × 10-6 mol L-1, was obtained. The detection limit and the limit of quantification were, respectively, 10 nmol L-1 and 40 nmol L-1. A Nernstian slope of about -59 mV/dec was achieved. The method has precision and LOD required for MCPA determination in contaminated environmental samples.

Voltammetric Detection of Irbesartan by Molecularly Imprinted Polymer (MIP)-Modified Screen-Printed Electrodes

Irbesartan is a drug used to treat hypertension and high blood pressure. Recent studies associated sartans with several forms of cancer, making removing this class of substances from the environment a high priority. The EU has categorized drugs as emerging pollutants, and they can be more potent than other substances because they were designed to operate at low concentrations. Thus, effective and sensitive methods of determining Irbesartan selectively and accurately in environmental samples are necessary. MIPs have already been used to remove pollutants from complex matrixes, so they were also chosen for this work. In particular, a polyacrylate-based MIP was used to functionalize the graphite working electrode of screen-printed cells (SPCs), aiming to develop a voltammetric method for Irbesartan sensing. The MIP composition and the experimental conditions for the electrochemical determination were optimized through a Design of Experiments (DoE) approach. The whole analysis was replicated with different SPCs obtaining similar results, which highlight the good reproducibility potential. MIP-based electrodes were also applied to determine Irbesartan in fortified tap water samples, obtaining high recovery percentages. Given the good results, the electrochemical method based on MIP-modified screen-printed electrodes is promising for quantifying Irbesartan at a trace level.

Screen-Printed Gold Electrode Functionalized with Deferoxamine for Iron(III) Detection

Deferoxamine (DFO), a hydroxamic siderophore with a high affinity for Fe(III), is immobilized as a functionalized self-assembled monolayer of a thiol (SAM) on the gold surface of a screen-printed cell to develop a voltammetric sensor for iron(III). The surface of the working electrode was characterized, before and after functionalization, by determining surface properties such as the area and the double-layer capacitance. The Fe(III) detection was performed by DPV analysis after preconcentration of the cation at the open circuit potential in solution at pH = 1 for two minutes. The method was applied to the iron(III) quantification in water samples giving promising results.

A MIP-based low-cost electrochemical sensor for 2-furaldehyde detection in beverages

There is an increasing interest in determining the concentration of furanic compounds naturally formed in food aqueous matrices, by in situ, fast and low-cost methods. A sensor presenting such characteristics is here proposed, and characterized. It is based on a molecularly imprinted polymer (MIP) as a receptor with electrochemical transduction on a screen printed cell (SPC). The molecularly imprinted polymer has been developed for a particular furanic derivative, 2-furaldehyde (2-FAL). The detection bases on the reduction of 2-FAL selectively adsorbed on the polymer layer in contact with the working electrode. The polymer layer is simply formed by in situ polymerization, directly over the SPC and it was characterized by IR, SEM and electrochemical methods. Even if based on an easy and fast preparation procedure, the layer sufficiently adheres to the cell surface giving a reusable sensor. Square wave voltammetry (SWV) was applied as the signal acquisition method. The sensor performance in aqueous solution (NaCl 0.1 M) was tested, obtaining that the dose-response curve is fitted by the Langmuir adsorption isotherm. The sensitivity, and so the limit of detection, were noticeably improved by a chemometric approach based on the Design of experiment method. (optimized conditions: Estep = 0.03 V, Epulse = 0.066 V, f = 31 s−1). In water solution at pH around neutrality the dynamic range was from about 50 μM to 20 mM. Similar results were obtained for a white wine containing 12% ethanol, which has been considered as a typical example of beverage possibly containing furhaldehydes. The higher limit of quantification can be modulated by the amount of MIP deposited, while the lower detection limit by the conditions of the electrochemical measurement.

Finger Metallization Using Pattern Transfer Printing Technology for c-Si Solar Cell

Front metallization of crystalline silicon solar cells requires smaller finger lines in order to collect the generated current from the active area efficiently. Pattern transfer printing (PTP) technology enables finger widths down to 20 μm and aspect ratios above 0.6 using thick film silver paste. This work investigates the influence of PTP process parameters, i.e., laser power and trench geometry, on the finger geometry and the print quality. Silver fingers obtained from four different trench geometries were analyzed and the electrical parameters of corresponding printed solar cells were compared with standard screen-printed solar cells. We observed a strong dependence of the finger aspect ratio and the amount of debris on the laser power that was used during the transfer process. Each trench geometry requires a different laser power, which is related to the ratio between the circumference and the horizontal interface of the trench. Despite a modest FF loss due to higher series resistance, a significant gain in Jsc and a smaller gain in Voc increased the cell efficiency by 0.12%abs for the best group of PTP-printed cells compared with the reference screen-printed cells. Importantly, the amount of silver required was reduced by 54% compared with the screen-printed reference.

A Comprehensive Evaluation of Contact Recombination and Contact Resistivity Losses in Industrial Silicon Solar Cells

Reliable characterization techniques to accurately quantify the metallization-induced recombination losses as well as contact resistivity losses of screen-printed cells are crucial for successful optimization of the contact grid design. Previously, the dark saturation current density at the contact ( ${J}_{\rm 0c}$ ) is often assumed to be constant for different finger width. Similarly, impact of finger width on contact resistivity ( ${\rho }_{\rm c}$ ) is rarely reported. Therefore, we performed a comprehensive evaluation of ${J}_{\rm 0c}$ and ${\rho }_{\rm c}$ as a function of finger width, spacing as well as firing temperature. We found out that ${J}_{\rm 0c}$ increases from $\approx$ 2000 to $\approx$ 8100 $\text{fA/cm}^{2}$ , when the finger width increases from 60 to 400 $\mu$ m; and ${\rho }_{\rm c}$ decrease from 7.2 to 2.2 $\text{m}{\Omega }\cdot \text{cm}^{2}$ when using a wide -TLM rather than a narrow -TLM structure, for samples fired at 840 $^{\circ }$ C. Based on our cross-sectional and top-down scanning electron microscopy images, we believe that the physical root cause can be explained by the difference in the microstructure formed at the metal–silicon interface during the firing process for the screen-printed contacts.

Electrochemical enzyme-linked oligonucleotide array for aflatoxin B1 detection

In this work, an electrochemical enzyme-linked oligonucleotide array to achieve simple and rapid multidetection of aflatoxin B1 (AFB1) is presented. The assay is based on a competitive format and disposable screen-printed cells (SPCs). Firstly, the electrodeposition of poly(aniline-anthranilic acid) copolymer (PANI-PAA) on graphite screen-printed working electrodes was performed by means of cyclic voltammetry (CV). Aflatoxin B1 conjugated with bovine serum albumin (AFB1-BSA) was then immobilized by covalent binding on PANI-PAA copolymer. After performing the affinity reaction between AFB1 and the biotinylated DNA-aptamer (apt-BIO), the solution was dropped on the modified SPCs and the competition was carried out. The biotinylated complexes formed onto the sensor surface were coupled with a streptavidin-alkaline phosphatase conjugate. 1-naphthyl phosphate was used as enzymatic substrate; the electroactive product was detected by differential pulse voltammetry (DPV). The response of the enzyme-linked oligonucleotide assay was signal-off, according to the competitive format. A dose-response curve was obtained between 0.1 ng mL−1 and 10 ng mL−1 and a limit of detection of 0.086 ng mL−1 was achieved. Finally, preliminary experiments in maize flour samples spiked with AFB1 were also performed.

Phosphorous-Doped Silicon Carbide as Front-Side Full-Area Passivating Contact for Double-Side Contacted c-Si Solar Cells

We present an electron selective passivating contact based on a tunneling SiO $_x$ capped with a phosphorous doped silicon carbide and prepared with a high-temperature thermal anneal. We investigate in detail the effects of the preparation conditions of the SiC $_x$ (n) (i.e., gas flow precursor and annealing temperature) on the interface recombination rate, dopant in-diffusion, and optical properties using test structures and solar cells. On test structures, our investigation reveals that the samples annealed at temperatures of 800–850 °C exhibit an increased surface passivation toward higher gas flow ratio ( r = CH4/(SiH4 + CH4)). On textured and planar samples, we obtained best implied open-circuit voltages ( i-V OC) of 737 and 746 mV, respectively, with corresponding dark saturation current densities ( J0 ) of ∼8 and ∼4 fA/cm2. The SiC $_x$ (n) layers with different r values were applied on the textured front side of p-type c-Si solar cells in combination with a boron-doped SiC $_x$ (p) as rear hole selective passivating contact. Our cell results show a tradeoff between V OC and short-circuit current density ( J SC) dictated by the C-content in the front-side SiC $_x$ (n). On p-type wafers, best V OC = 706 mV, FF = 80.2%, and J SC = 38.0 mA/cm2 with a final conversion efficiency of 21.5% are demonstrated for 2 × 2 cm2 screen-printed cells, with a simple and patterning-free process based on plasma depositions and one annealing step 800 °C T < 850 °C for the formation of both passivating contacts.

High-Efficiency Screen-Printed p-Si Interdigitated Back Contact Cells: Fabrication and Analytical Characterization

In this paper, we report on the fabrication and analytical characterization of the screen-printed p-Si interdigitated back contact (IBC) cells with the conversion efficiency of 20.08%, with open-circuit voltage of 645 mV, short-circuit current density of 40.15 mA/cm2, and fill factor of 77.51%. The cell performance has also been confirmed with the analytical calculation based on the electrical properties measured. It also shows that, with the proper emitter design, the open-circuit voltage of 680 mV and conversion efficiency of 22% are readily attainable for the screen-printed p-Si IBC cell. Compared with the screen-printed IBC cells, the passivated emitter and rear “contact” cell may perform equivalently well, provided that any improvement on S eff of the front surface does not compromise the light absorption and emitter resistance of the cell.

Defect passivation on cast-mono crystalline screen-printed cells

Cast-mono crystalline silicon wafers contain crystallographic defects, which can severely impact the electrical performance of solar cells. This paper demonstrates that applying hydrogenation processes at moderate temperatures to finished screen print cells can passivate dislocation clusters within the cast-mono crystalline silicon wafers far better than the hydrogenation received during standard commercial firing conditions. Efficiency enhancements of up to 2% absolute are demonstrated on wafers with high dislocation densities. The impact of illumination to manipulate the charge state of hydrogen during annealing is investigated and found to not be significant on the wafers used in this study. This finding is contrary to a previous study on similar wafers that concluded increased H– or H0 from laser illumination was responsible for the further passivation of positively charged dangling bonds within the dislocation clusters.

Single Print Metal Stencils for High-efficiency PERC Solar Cells

Industrial silicon solar cells like Passivated Emitter and Rear Cells (PERC) typically apply a screen-printed (Ag) front contact with a single print process using a mesh screen. It has been shown that using stencils instead of screens improves the finger profile leading to slightly higher cell conversion efficiencies. However, so far stencil printing required an extra printing step for the busbars since conventional stencils do not support H-pattern designs. In this paper, we evaluate a novel “single print” stencil from ASM AE that allows to print busbars and fingers in a single print step. We apply the novel single print stencil to high-efficiency PERC solar cells and compare it to today's industrial screen printing processes (single print and dual print) as well as to a high performance dual-printed front side grid applying a stencil for the fingers and a screen for the busbars. The printed finger width ranges from 35.8 ± 2.3μm for 30μm stencil opening to 46.7 ± 3.4μm for 40μm screen opening which leads to an 0.5%abs increased metallized area on the front side of the screen printed fingers compared to the stencil printed fingers. The resulting average finger height is 22.3μm for the stencil groups and 11.9μm for the screen printed Ag finger which leads to a difference in the finger line resistance and an additional series resistance contribution for the screen-printed cells of 0.05Ωcm2. We achieve almost identical PERC cell efficiencies with the single print stencil and the dual print stencil process obtaining best values up to 21.1% and average values of 21.0%. In contrast, both screen printed groups achieve 0.2%abs lower average conversion efficiencies mostly due to the lower Jsc and FF. The advantage of the dual print process compared to single print is shown in the increased Voc by 1 to 2mV due to the used non-firing through Ag busbar paste. With these results we demonstrate that the single print stencil process saves two process steps compared to dual print using a stencil while obtaining the same PERC cell performance with an efficiency gain of 0.2%abs compared to today's industrial screen print processes.

Ion-Implanted Screen-Printed n-Type Solar Cell With Tunnel Oxide Passivated Back Contact

This paper shows the results and the limitations of a 21% N-Cz 239-cm2 screen-printed cell with blanket p+ emitter and n+ back surface field. In addition, we show the properties and impact of tunnel oxide capped with doped n+ polysilicon and metal on the back side, which can overcome those limitations. Since both the doped n+ layer and the metal contact are outside the bulk silicon wafer, the Jo is dramatically reduced, resulting in much higher $V_{{\rm oc}}$ . Process optimization has resulted in high $iV_{{\rm oc}}$ of 728 mV on symmetric structures. The unmetallized cell structure with Al2O3/SiN passivated lightly doped p+ emitter and a tunnel oxide/n+ poly back also gave high $iV_{{\rm oc}}$ of 734 mV. The finished screen-printed 132-cm2 device gave a $V_{{\rm oc}}$ of 683 mV, $J_{{\rm sc}}$ of 39.4 mA/cm2, FF of 77.6%, and an efficiency of 20.9%. Cell analysis show that implementation of a selective emitter can give higher efficiency.

Bimodally dispersed silver paste for the metallization of a crystalline silicon solar cell using electrohydrodynamic jet printing

Conventional silver paste for crystalline silicon solar cells exhibits low cell efficiency when deposited by non-contact electrohydrodynamic jet printing because of either high volumetric shrinkage or low packing density when there is no printing pressure applied to the silver paste. Therefore, we develop bimodally dispersed silver paste for electrohydrodynamic jet printing to resolve both volumetric shrinkage and packing density of the conventional silver paste, and its electrical and rheological traits are investigated. The bimodally dispersed silver paste exhibits lower unit-line resistance, which is inversely proportional to the weight ratio of small-to-large silver particles due to the increased packing density, and higher contact resistivity above a certain weight ratio for small-to-large silver particles. This behaviour results from the obstructed melt flow of glass frit by the early coarsened and densified small silver particles at an elevated temperature. The increased weight ratio of the small particles also raises the viscosity of the bimodally dispersed silver paste above the point where electrohydrodynamic jet printing is possible. By employing a binary solvent mixture and metallorganic silver as a viscosity reducing agent, the bimodally dispersed silver paste is tuned for electrohydrodynamic jet printing, and the front-side metallization of a polycrystalline silicon solar cell with the emitter sheet resistance of 60Ω/sq is constructed. With the abnormally high aspect ratio of silver electrodes at 0.86, a cell efficiency of 16.72% is achieved, which is higher than that of screen-printed cells with the similar emitter sheet resistance by +0.22–0.52%p.

Preparation of (BaSr)&lt;sub&gt;0.5&lt;/sub&gt;Sm&lt;sub&gt;0.5&lt;/sub&gt;C&lt;sub&gt;0.8&lt;/sub&gt;Fe&lt;sub&gt;0.2&lt;/sub&gt;O&lt;sub&gt;3-δ&lt;/sub&gt; and (BaSr)&lt;sub&gt;0.5&lt;/sub&gt;Nd&lt;sub&gt;0.5&lt;/sub&gt;C&lt;sub&gt;0.8&lt;/sub&gt;Fe&lt;sub&gt;0.2&lt;/sub&gt;O&lt;sub&gt;3-δ&lt;/sub&gt; Cathodes for IT-SOFCs

The development of electrochemical devices towards clean energy generation has been intensified in the last years. In this context, fuel cells, and especially intermediate temperature solid oxide fuel cells (IT-SOFC) have received much attention. Perovskite type materials of composition Ba1-xSrxCo1-yFeyO3-δ, doped or not with rare earth ions, have been quite promising because they have good ionic conductivity and operate at relatively low temperatures (500 750 °C). In this study, powders of compositions (BaSr)0.5Sm0.5Co0.8Fe0.2O3-δ (BSSCF) and (BaSr)0.5Nd0.5Co0.8Fe0.2O3-δ (BSNCF) were prepared using commercial gelatin powder as a polymerizing agent for its use as cathode. The as-prepared powders were calcined at 1000 oC and characterized by X-ray diffraction and scanning electron microscopy. Screen-printed symmetrical cells were sintered 1150 °C and studied by electrochemical impedance spectroscopy in order to assess the cathode kinetics for the oxygen reduction reaction. The best area specific resistance was found for the BSSCF cathode sintered at 1150 °C for 4 h (0.157 Ω.cm2 at 750 °C), demonstrating that this novel composition is suitable for application as SOFC cathode material. key words: Cathode, microstructure, impedance spectroscopy, IT-SOFC.

Disposable biosensor based on cathodic electrochemiluminescence of tris(2,2-bipyridine)ruthenium(II) for uric acid determination

A new method for uric acid (UA) determination based on the quenching of the cathodic ECL of the tris(2,2-bipyridine)ruthenium(II)–uricase system is described. The biosensor is based on a double-layer design containing first tris(2,2-bipyridine)ruthenium(II) (Ru(bpy)32+) electrochemically immobilized on graphite screen-printed cells and uricase in chitosan as a second layer. The uric acid biosensing is based on the ECL quenching produced by uric acid over the cathodic ECL caused by immobilized Ru(bpy)32+ in the presence of uricase. The use of a −1.1V pulse for 1s with a dwelling time of 10s makes it possible to estimate the initial enzymatic rate, which is used as the analytical signal. The Stern–Volmer type calibration function shows a dynamic range from 1.0×10−5 to 1.0×10−3M with a limit of detection of 3.1×10−6M and an accuracy of 13.6% (1.0×10−4M, n=5) as relative standard deviation. Satisfactory results were obtained for urine samples, creating an affordable alternative for uric acid determination.

Capitalising on the Precisions of Ion Implantation and Ink Jetted Fine Gridline to Create Low-Cost High Efficiency Silicon Solar Cells

This paper reports ink-jetted gridline, production ready, solar cells with ion implanted homogeneous high sheet resistance emitters having efficiency of >19%. The average efficiency of ∼18.96% on 80 ohm/square ion implanted emitter with highest efficiency of 19.2% demonstrates the potential of combining the two high precision technologies, inkjet printing and ion implantation. The key attributes of the cells include average open circuit voltage (VOC) of 640mV, fill factor (FF) of 79.14% and short circuit current density (JSC) of 37.8mA/cm2. Worthy of note is that, the front gridlines width and height of 47.6μm and 43.9μm resulting in aspect ratio of 0.92 using only 83mg total Ag, which is, at least 20% Ag less than today's screen printed cells. However, the reference screen-printed cells showed similar average efficiency with the best gridline widths of ∼70μm and height of ∼28μm used >100mg of Ag. Statistical analysis illustrates that the highest efficiency with the screen-printed contacts is an outlier as the minimum efficiency for the ink-jetted group. This efficiency is very significant because all cells were fabricated on a pilot production line at Shanghai Shengzhou New Energy Co. Ltd, in China.