Mirjana Rajčić-Vujasinović

Cuprous Oxide as an Active Material for Solar Cells

Growing demand for energy sources that are cleaner and more economical led to intensive research on alternative energy sources such as rechargeable lithium batteries and solar cells, especially those in which the suns energy is transformed into electrical or chemical. From the ecology point of view, using solar energy does not disturb the thermal balance of our planet, either being directly converted into heat in solar collectors or being transformed into electrical or chemical energy in solar cells and batteries. On the other hand, every kilowatt hour of energy thus obtained replaces a certain amount of fossil or nuclear fuel and mitigates any associated adverse effects known. Solar energy is considered to be one of the most sustainable energy resources for future energy supplies. To make the energy of solar radiation converted into electricity, materials that behave as semiconductors are used. Semiconductive properties of copper sulfides and copper oxides, as well as compounds of chalcopyrite type have been extensively investigated (RajcicVujasinovic et al., 1994, 1999). One of the important design criteria in the development of an effective solar cell is to maximize its efficiency in converting sunlight to electricity. A photovoltaic cell consists of a light absorbing material which is connected to an external circuit in an asymmetric manner. Charge carriers are generated in the material by the absorption of photons of light, and are driven towards one or other of the contacts by the built-in spatial asymmetry. This light driven charge separation establishes a photo voltage at open circuit, and generates a photocurrent at short circuit. When a load is connected to the external circuit, the cell produces both current and voltage and can do electrical work. Solar technology, thanks to its advantages regarding the preservation of the planetary energy balance, is getting into an increasing number of application areas. So, for example, Rizzo et al. (2010) as well as Stevic & Rajcic-Vujasinovic (in Press)describe hybrid solar vehicles, while Vieira & Mota (2010) show a rechargeable battery with photovoltaic panels. The high cost of silicon solar cells forces the development of new photovoltaic devices utilizing cheap and non-toxic materials prepared by energy-efficient processes. The Cu–O system has two stable oxides: cupric oxide (CuO) and cuprous oxide (Cu2O). These two oxides are semiconductors with band gaps in the visible or near infrared regions. Copper and copper oxide (metal-semiconductor) are one of the first photovoltaic cells invented (Pollack and Trivich, 1975). Cuprous oxide (Cu2O) is an attractive semiconductor material that could be

Temperature effect on decorative gold coatings obtained from electrolyte based on mercaptotriazole – comparison with cyanide

Abstract The aim of this work was to investigate the effect of temperature on the thickness, surface roughness, visual appearance and morphology of electrochemically deposited gold decorative coatings obtained from conventional cyanide electrolyte (AUROCIN DPB) and electrolyte based on mercaptotriazole (Au-MT). Heating of cyanide electrolyte does not significantly affect the thickness (b) of gold coatings (at 20 °C b = 0.08 μm, at 30 °C b = 0.07 μm and at 40 °C b = 0.08 μm) and, for this reason, the decorative coating processes were carried out at room temperature. Temperature increase has a positive effect on thickness of decorative gold coatings obtained from electrolyte based on mercaptotriazole, but this effect is very small, so the heating of electrolyte is not recommended for this type of electrolyte (at 20 °C b = 0.08 μm, at 40 °C b = 0.12 μm and at 60 °C b = 0.13 μm). The best coating roughness profiles are obtained at a temperature of 20 °C for both types of electrolyte. The morphology of gold deposits, obtained from both electrolytes, was studied using scanning electron microscopy.

Electrochemical behavior of alloy AgCu50 during oxidation in the presence of chlorides and benzotriazole

Abstract The presence of chloride ions in concentrations higher than 0.01 mol × dm−3 significantly intensifies anodic processes at AgCu50 alloy. In order to slow down this reaction, it was looked for the possibility of using benzotriazole known as an effective corrosion inhibitor for copper. This paper shows the influence of benzotriazole in a wide range of concentrations on inhibition of anodic processes as well as its influence on mechanism of the reactions such as formation of copper and silver oxides and chlorides. To determine this influence, open circuit potential measurements, anodic polarization and potentiostatic oxidation followed by optical microscopy were used. It was discovered that benzotriazole in concentrations higher than 0.005 mol × dm−3 almost completely passivates the mentioned alloy in alkaline solutions in the presence of chloride ions in a concentration range from 0.01 to 0.02 mol × dm−3.

Microhardness of decorative gold coatings obtained from gold complex based on mercaptotriazole: Comparison with cyanide

Abstract The aim of this work was to investigate the effects of current density, temperature, pH and concentration of ethylhexilsulfonate additive on the microhardness of electrochemically deposited gold decorative coatings obtained from a conventional cyanide electrolyte and gold complex based on mercaptotriazole. Mechanically and chemically prepared brass samples were first nickeled from acidic electrolyte. Nickel was a substrate deposit, and then decorative gold coatings were deposited from two types of electrolytes at different current densities and temperatures. Decorative gold coatings were deposited from auri-mercaptotrizole at different pH values and from electrolyte with and without the ethylhexilsulfonate additive. The microhardness of the gold coating was measured using the Knoop method. The highest values of microhardness were obtained at a current density of 1 A dm−2 at room temperature for both electrolytes. The microhardness of the gold coatings from cyanide electrolytes was HK = 740 MPa, and the coatings obtained from auri-mercaptotriazole HK = 660 MPa. This difference is not relevant for decorative purposes. The highest values of microhardness, HK = 660 MPa, were obtained at pH = 9 from the gold complex based on mercaptotriazole without the additive.

System for characterization of supercapacitors

The hardware and software system, based on LabVIEW package, for electrical investigations of supercapacitors was developed. The system provides standard testing (cyclic voltammetry, constant current charge and discharge, electrochemical impedance spectroscopy, etc.) of supercapacitors in the temperature range of 30 to 100° C and under pressure up to 3 bars. The effectiveness of the system was verified.

The influence of novel organic gold complex on photoresist layers of printed circuit boards

The goal of this paper was to study the influence of organic gold complex based on mercaptotriazole on photoresist layers used in manufacturing of printed circuit boards (PCBs). Investigations were performed by immersion the previously prepared boards in electrolytes with different pH values (pH=2, 4, 7, 9 and 12) at gold concentration of 2.5 g/dm3 and in gold complexes with different gold concentrations (1.5; 2.0; 2.5; 3.0 and 3.5 g/dm3) at pH value of pH=9. Investigations showed that photoresist layers on boards are the most resistant at optimal operating conditions, pH=9 and concentration of gold of 2.5 g/dm3.