Vladimir Saly

The preparation of tetracyanonickelates showing electrical conductivity

The tetracyanonickelates Ni(NH3)2Ni(CN)4·1.9 H2O (1), Ni(NH3)1.65(C4H8O2)0.2Ni(CN)4·0.8 C4H8O2·0.35 H2O (2) and Ni(en)3Ni(CN)4·H2O (3) exhibit, after contact with a solution of iodine (I2/KI), appreciable weight gains. According to thermal analysis, IR spectra and chemical analysis the new products contain intercalated iodine and iodides with the highest iodine content found in the product formed from (3). The results of high frequency conductance measurements of this product showed the highest value of electrical conductivity σ (10−6 S cm−1). Other compounds show relatively low values of σ (10−8–10−11 S cm−1).The iodine together with its iodide and polyiodide forms enters host (3) as an intercalated species. The iodide and polyiodide forms are formed during the initial redox reactions between the NH group of the ethylenediamine and the iodine.

Microstructure and physical properties of transparent thoria-yttria ceramics

The investigation of microstructure, some electrical and optical parameters of transparent ThO2-15 mol % yo1.5 ceramics has shown: (a) a very low porosity, close to zero; (b) a higher electrical conductivity than is usual for ThO2 ceramics of the same composition, with the activation energy 1.12 eV; (c) a relative permittivity ɛr ∼ 33 under the given conditions; (d) confirmation of a single-phase fluorite-type cubic structure by means of Raman and infrared spectra.

Solar cell heterojunction a-SiC:H/c-Si structure under dark and illumination

Thin films of p-doped amorphous SiC used as an emitter layer for heterojunction solar cells have been the subject of this work. Thin amorphous SiC films were prepared by PECVD technology. Impact of dopation on the resulting properties of heterojunction was the main object of this study. The DC measurements under dark were performed in order to detect basic electronic properties as a diode ideality factor and saturation current. PV parameters such as fill factor, open circuit voltage and efficiency were obtained from DC measurements under illumination. The impedance spectroscopy analysis was performed by following Cole-Cole principle.

PV concentrator cells complex impedance under the bias in the dark

Crystalline silicon solar cells of standard design and such modified for concentrator application were studied. This work presents a complex impedance technique and its application on PV cell study. The general form of the impedance describes a semicircular locus in the complex impedance plane. Temperature variation influence or superposed DC voltage is known and standardly studied in order to describe equivalent circuit elements behavior. The calculated results obtained from impedance data, as shunt resistances and capacitances, are presented in our work. The dynamic impedance of non-concentrator crystalline silicon PV cell was determined and was compared with those obtained on concentrator cells in the dark with different bias voltage and over a frequency range of 42 Hz to 130 kHz. The experimental results confirm the derived general form of dynamic impedance

Electrical characterization of PV modules after three years of operation

Small PV system installed on the roof of Faculty of Electrical Engineering and Information Technology building in Bratislava has been monitored during three years and its parameters determined. After three years of operation time the changes in photovoltaic module properties have been evaluated by means of various electrical measurements and ageing process estimated using the capacitance, dissipation factor, insulation resistance and polarisation index, their temperature dependences and charging current measurements and compared on aged and non-aged modules.

FTIR spectroscopy of silicon carbide thin films prepared by PECVD technology for solar cell application

The plasma CVD reactor with parallel plate electrodes was used for plasma enhanced chemical vapor deposition (PECVD) of two type’s silicon carbide thin films on Si substrates. The concentration of elements in the films was determined by RBS and ERD analytical method simultaneously. The chemical compositions of the samples were analyzed by FTIR method. RBS and ERD results showed that the films contain silicon, carbon, hydrogen and small amount of oxygen. FTIR results confirmed the presence of Si-C, Si-H, C-H, and Si-O bonds. From the FTIR spectra the main following vibration frequencies were determined: the band from 2800 to 3000 cm-1 is attributed to stretching vibration of the CHn group in both the sp2 (2880 cm-1) and sp3 (2920 cm-1) configurations. The band at 2100 cm-1 is due to SiHm stretching vibrations. The band at 780 cm-1 can be assigned to Si-C stretching vibration. Main features of FTIR spectra were Gaussian fitted and detailed analyses of chemical bonding in SiC films were performed. Differences between two types of SiC films were discussed with the aim to using these films in the heterojunction solar cell technology.

RECOVERY OF WASTE USING THE GASIFICATION AND OXIDATION OF SCRAP TIRES

The investigation of the use of microwave gasification as a method that allows to obtain energy from end-of-life (ELTs) tires was subject of this study. The gasification of the waste was carried out within the laboratory microwave reactor HR – Lab, followed by the microwave-assisted oxidation of synthesis gas (syngas) which took place in a small microwave reactor – Microwave Oxidation System (MOS). Details of the experiment, such as power and temperature profile as a function of time and material charges distribution, are listed and explained. Analysis of gasification produced syngas in terms of composition and energy values was done also.

Electrical characterization of a-SiC/c-Si solar cell structures

The heterojunction solar cell structure consists of thin doped amorphous SiC layer and crystalline n-type silicon. Dark and light current-voltage (I-V) measurements were performed in order to obtained basic electric and PV parameters of prepared solar cell structures. Biased complex impedance spectra of Al/a-SiC/c-Si(n)/Al heterojunction in the dark are reported and analyzed. AC equivalent circuit was obtained by fitting of impedance dependences and its electronic components were used to describe the electronic transport properties of prepared structures.

Diagnostics and testing of photovoltaic devices

The aim of this paper is the investigation of electrical and acoustic properties of solar cells assembled into modules, before and after forced and accelerated ageing. It has been shown that impedance spectroscopy measurement and characterization is an important tool to reveal the degradation changes due to high voltage stress and environmental stress. The parameters of photovoltaic (PV) cells and modules have been derived from electric and acoustic measurements. Important differences between the results of measurements have been found before and after the PV cells and modules underwent the stressing.

Electrical behaviour of CaO-doped ThO2

The total a.c. conductivity of a CaxTh1−xO2−x solid solution with fluorite-type structure was measured at 1360 Hz with 0⩽x⩽0.25 and at temperatures of 100 to 600° C. The complex impedance behaviour was investigated at frequencies of 10 to 105 Hz and temperatures of 300 to 500° C. The complex dielectric permittivity was calculated at this frequency and in that temperature range. The activation energy for the bulk conductivity was calculated. Its value is about 1.48 eV forx<0.03 and about 1.25 forx⩾0.03.