Wojciech Filipowski

Comparison of diffused layer prepared using liquid dopant solutions and pastes for solar cell with screen printed electrodes

Purpose The purpose of this study is comparison of the diffusion processes performed using the commercial available dopant paste made by Filmtronics and the original prepared liquid dopant solution. To decrease prices of industrially produced silicon-based solar cells, the new low-cost production processes are necessary. The main components of most popular silicon solar cells are with diffused emitter layer, passivation, anti-reflective layers and metal electrodes. This type of cells is prepared usually using phosphorus oxychloride diffusion source and metal pastes for screen printing. The diffusion process in diffusion furnace with quartz tube is slow, complicated and requires expensive equipment. The alternative for this technology is very fast in-line processing using the belt furnaces as an equipment. This approach requires different dopant sources. Design/methodology/approach In this work, the diffusion processes were made for two different types of dopant sources. The first one was the commercial available dopant paste from Filmtronics and the second one was the original prepared liquid dopant solution. The investigation was focused on dopant sources fabrication and diffusion processes. The doping solution was made in two stages. In the first stage, a base solution (without dopants) was made: dropwise deionized (DI) water and ethyl alcohol were added to a solution consisting of tetraethoxysilane (TEOS) and 99.8 per cent ethyl alcohol. Next, to the base solution, orthophosphoric acid dissolved in ethyl alcohol was added. Findings Diffused emitter layers with sheet resistance around 60 Ω/sq were produced on solar grade monocrystalline silicon wafers using two types of dopant sources. Originality/value In this work, the diffusion processes were made for two different types of dopant sources. The first one was the commercial available dopant paste from Filmtronics and the second one was the original prepared liquid dopant solution.

Statistical Analysis of the Impact of Molecular Descriptors on Cytotoxicity of Thiourea Derivatives Incorporating 2-Aminothiazole Scaffold

Chemical reactivity descriptors and lipophilicyty (log P) were evaluated via semi-empirical method for the quantum calculation of molecular electronic structure (PM3) in order to clarify the structure-cytotoxic activity relationships of disubstutited thioureas. Analysed compounds were obtained by the linkage of 2-aminothiazole ring, thiourea and substituted phenyl ring. The detailed examination was carried out to establish correlation between descriptors and cytotoxic activity against the MT-4 cells for 11 compounds. For the most active compounds (6 compounds) cytotoxic activity against three cancer cell lines (CCRF-CEM, WIL-2NS, CCRF-SB) and normal human cell (HaCaT) was determined. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction and lactate dehydrogenase (LDH) release were assessed. Regression analysis revealed that electrophilicity index and chemical potential significantly contributed to expain the thioureas cytotoxic potential.

Spray-on glass solution for fabrication silicon solar cell emitter layer

Purpose The main aim of this study was a preparation development of dopant solution (DS) which can be deposited by a spray-on method and subsequently allows obtaining the n+ emitter layer with surface resistance in the range of 65-80 Ω−1. The intention of chosen spray-on method was to gain a cheaper way of dopant source deposition, compared to the commonly used methods, which is of particular importance for the new low-cost production processes. Design/methodology/approach This paper presents the sequence in producing a spray-on glass solution (DS) with very high concentration of phosphorus, which allows to perform diffusion doping at relatively low temperatures. DS contained deionized water, ethyl alcohol, tetraethoxysilane and othophosphoric acid. Findings The sequence in producing a DS was performed with respect to enabling the application to silicon wafers by spray-on method. Furthermore, the equations defined density and viscosity of DS in term of storage time were referred to determine the possibility of applying this solution by spray-on method. Besides, the dependence of the emitter surface resistance on the doping (diffusion) time was determined. Accordingly, optimal process conditions were specified. Originality/value The paper presents a new, so far unpublished composition of DS with very high concentration of phosphorus, which can be applied using a spray-on method. Moreover, original are also investigations respecting some properties of obtained DS relative to storage time.

The Diffusion of Viral Content in Multi-layered Social Networks

Modelling the diffusion of information is one of the key areas related to activity within social networks. In this field, there is recent research associated with the use of community detection algorithms and the analysis of how the structure of communities is affecting the spread of information. The purpose of this article is to examine the mechanisms of diffusion of viral content with particular emphasis on cross community diffusion.

Study of Structure-Cytotoxicity Relationships of Thiourea Derivatives Containing the 2-Aminothiazole Moiety

In order to facilitate designing new drugs by means of the in silico method, it is necessary to first develop a model describing the influence of descriptors of a certain group of chemicals on their biological activity and cytotoxicity. For the purpose of this paper, the quantitative structure-cytotoxicity relationships have been determined for 11 thiourea derivatives containing the 2-aminothiazole moiety and demonstrating varied cytotoxicity against MT-4 cells. The statistical analyses were conducted by means of Multiple Linear Regression (MLR). This paper contains linear models of cytotoxicity depending on electronic, steric and lipophilic descriptors of the examined compounds containing the 2-aminothiazole moiety. The models have been validated by means of the Leave-One-Out Cross Validation (LOO CV).

Synthesis, Structural Studies and Biological Evaluation of Connections of Thiosemicarbazide, 1,2,4-Triazole and 1,3,4-Thiadiazole with Palmitic Acid

Thirty new derivatives of palmitic acid were efficiently synthesized. All obtained compounds can be divided into three groups of derivatives: Thiosemicarbazides (compounds 1–10), 1,2,4-triazoles (compounds 1a–10a) and 1,3,4-thiadiazoles (compounds 1b–10b) moieties. 1H-NMR, 13C-NMR and MS methods were used to confirm the structure of derivatives. All obtained compounds were tested in vitro against a number of microorganisms, including Gram-positive cocci, Gram-negative rods and Candida albicans. Compounds 4, 5, 6, 8 showed significant inhibition against C. albicans. The range of MIC values was 50–1.56 μg/mL. The halogen atom, especially at the 3rd position of the phenyl group was significantly important for antifungal activity. The biological activity against Candida albicans and selected molecular descriptors were used as a basis for QSAR models, that have been determined by means of multiple linear regression. The models have been validated by means of the Leave-One-Out Cross Validation. The obtained QSAR models were characterized by high determination coefficients and good prediction power.

Relationship between resistance, TCR and stabilization temperature of amorphous Ni-P alloy

Purpose The paper aims to present a research on the impact of the stabilization process of a thin metallic layer (Ni-P) produced on a ceramic surface (Al2O3) by means of electroless metallization on its electric parameters and structure. On the basis of the research conducted, the existence of a relationship between resistance (R) and the temperature coefficient of resistance (TCR) of the test structure with a Ni-P alloy-based layer and the temperature of stabilization was proposed. Design/methodology/approach Metallic Ni-P layers were deposited on sensitized and activated substrates. Metallization was conducted in an aqueous solution containing two primary ingredients: sodium hypophosphite and nickel chloride. The concentration of both ingredients was (50-70) g/dm3. The process lasted 60 min, and the metallization bath pH was kept at 2.1-2.2, whereas the temperature was maintained at 363 K. The thermal stabilization process was conducted in different temperatures between 453 and 623 K. After the technological processes, the resistance and TCR of the test structures were measured with a micro ohmmeter. The composition and the morphology of the resistive layer of the structures examined was also determined. Findings The dependence of the resistance on the temperature of the stabilization process for the temperature range 553 to 623 K was described using mathematical relationships. The TCR of test resistors at the same thermal stabilization temperature range was also described using a mathematical equation. The measurements show that the resistive layer contains 82.01 at.% of nickel (Ni) and 17.99 at.% of phosphorus (P). Originality/value The results associate a surface morphology Ni-P alloy with the resistance and TCR according to temperature stabilization. The paper presents mathematical relationships that have not been described in the literature available.

Statistical Analysis of the Impact of Molecular Descriptors on Antimicrobial Activity of Thiourea Derivatives Incorporating 3-amino-1,2,4-triazole Scaffold

The paper contains results of statistical and chemometric analysis for 15 thiourea derivatives containing the 3-amino-1,2,4-triazole moiety and characterized by antimicrobial activity against Staphylococcus aureus (NCTC 4163, ATCC 25923, ATCC 6538, ATCC 29213), Staphylococcus epidermidis (ATCC 12228) bacteria, as well as by low cytotoxicity (or lack thereof) against infected MT-4 cells. Multiple regression and cluster analysis were employed to perform the study. The research enabled obtaining linear relationships connected with three molecular descriptors SA, η, logP. The conducted chemometric analyses indicate that the increase in activity against the studied strains is closely related to the type and position of substituent in a phenyl ring.

Electrical and optical properties of spin-coated SnO2 nanofilms

SnO2 nanocrystalline thin films have been deposited on oxidized silicon substrates by spin-coating from a precursor solution, followed by slow thermal annealing in oxygen atmosphere at different temperatures (500 to 900 °C). The precursor solution consisted of 1.0 to 2.0 M SnCl4·5H2O in isopropanol. It was shown that the concentration of the precursor solution, annealing temperature and heating rate had a significant effect on the structural, optical and electrical properties of the studied thin films. The topography of SnO2 thin films was examined by scanning electron microscopy (SEM). Furthermore, as-deposited films were characterized by X-ray diffraction (XRD), UV-Vis and impedance spectroscopy.

Density-based Community Identification and Visualisation

Community can be generally defined as a sub graph where nodes are more densely connected with each other than with the rest of a network. Such definition makes application of density-based clustering methods to community identification justified and natural. Moreover, density-based methods have many extensions enabling their application to complex data analysis. Therefore, the analysis of the characteristics of density-based clustering methods in application to community identification is important and valuable. The article presents and evaluates new similarity measures that can be utilised by the approaches to density-based community identification. Several experiments on real life and generated networks are performed to show and explain the differences between these measures and to compare them with other methods. The results show that the new measures improve the quality of analysis and that density-based clustering algorithms can be valuable community identification methods.