Z. Chobola

Noise as a tool for non-destructive testing of single-crystal silicon solar cells

Abstract Transport and noise characteristics of forward and reverse biased single-crystal silicon solar cells were measured in order to evaluate the solar cell technology. Stress comprising an temperature of 400 K and a DC electric field were applied to a total of 20 solar cells for a period of 5000 h. The samples were quality and reliability screened using noise reliability indicators. From the measurement results it follows that the noise spectral density related to defects is of 1/f type and its magnitude was found to be proportional to the square of the DC forward current at low injection levels. It has been established that samples showing low noise feature high-conversion efficiency. It has also been found out that there is a strong correlation between the sample initial-condition noise and the efficiency after 5000 h of combined stressing.

NOISE AND SCANNING BY LOCAL ILLUMINATION AS RELIABILITY ESTIMATION FOR SILICON SOLAR CELLS

This paper presents two methods, namely those using noise and homogeneity measurements of a large area solar cells, for determining the local defects, which bring down efficiency and long reliability of single-crystal silicon solar cells. As a result of the non-uniformities (non-homogeneity) in the large junction area, local areas with lower built-in potentials at the junction lead to hot spots and reduced reliability. The two techniques can be used to give a precise description of the quality of the product technology. Correlations between noise and inhomogeneities for an ensemble of 30 silicon solar cell samples are given.

Diode I-U Curve Fitting with Lambert W Function

Application of the Lambert W function in diode forward i-u curve fitting for the purpose of diode parameters determination is described. CFTOOL of Matlab7 is utilized. Fitting and its results are discussed. Semiconductor PN junction solar cells are used as the diode samples. Brief Lambert W function appendix is attached

1/f noise in metallic thin films

Studies of 1/fa noise in vast ensembles of thin film resistors are described. The distribution of the exponent a in the spectral density power law is found to be normal, the mean value being near unity and depending on the sample preparation technology. The scattering range of the values of a is typical of the resistor manufacturers. The noise voltage spectral density distribution is shown to depend on the frequency, being close to normal. The number of fluctuators is shown to be much less than the number of free electrons in the specimen.

Solar Cells Noise Diagnostic and LBIC Comparison

This paper is intended to present the results of our experimental study of defect in silicon solar cells. Solar cells defects are diagnosed by LBIC characterization and noise spectroscopy. Low frequency noise is a more sensitive tool for analyzing of degradation phenomena, like electro migration and sort of breakdown. All type of noise — thermal, shot, generation, recombination and 1/f type of noise play a different role in reliability analysis. The correlation between noise and transport characteristic indicates possibility of this diagnostic tool. Therefore the noise spectroscopy and LBIC is a pair of the very useful methods to provide a non‐destructive characterization on silicon semiconductor solar cells.

LOW-FREQUENCY NOISE MEASUREMENTS USED FOR QUALITY ASSESSMENT OF GaSb BASED LASER DIODES PREPARED BY MOLECULAR BEAM EPITAXY

Abstract The paper reports on a non-destructive method of reliability prediction for semiconductor lasers diodes GaSb based VCSE (vertical cavity surface emitting). Transport and noise characteristic of forward biased were measured in order to evaluate the new MBE (molecular beam epitaxy) technology. The results demonstrate that the lasers prepared by new MBE technology have higher quality than the samples prepared by using the classic MBE technology.

Impact-Echo Methods to Assessment Corrosion of Reinforced Concrete Structures

The aim of this paper is to evaluate the corrosion of reinforced concrete structure. To assess the state of corrosion we used frequency signal analysis, where we observed the changes in dominant frequencies and growth of damping factor λ. Tension pulse was produced in axis of the rod at one end and detected in axis at opposite end of rod. Diameter of steel rod was 8 mm. The article presents the results of measurements obtained during 24 months controlled degradation in aqueous NaCl solution.

Using of Impact-Echo Methods to Assessment of Reinforced Concrete Structures Corrosion

The paper deals with the study of dominant frequencies of an Impact-Echo method response signal obtained from a reinforced concrete beam with a steel rod diameter of 8 mm. Tension pulse was produced in axis of the rod at one end and detected in axis at opposite end of rod. Dominant frequencies of the response signal will be the main criterions for the reinforced concrete rebar corrosion progress. The article presents the results of measurements obtained after 12 months controlled degradation in aqueous NaCl solution. The results were compared with measurements of electrical resistance of reinforcing steel by using the Thomson double bridge.

High-Temperature Degradation of Mortar Containing Rubber Aggregates and EVA Binder Evaluated by Impact-Echo Method

The application of Impact-echo acoustic method to evaluate the degradation and the composition of mortar composites modified with rubber aggregates and EVA polymer binder degraded at high temperatures was studied. Specimens were prepared by using a type CEM I Portland cement and siliceous sand, as well as by substituting 25% of sand with shredded automobile tires and by adding of EVA polymer binder (10% w/w to cement mass). The samples were subjected to high-temperature treatment in the temperature range of 200-400 °C. The results of non-destructive testing of such samples by acoustic methods confirmed the differences in the structure of mortar specimens. Addition of rubber aggregates in samples caused absorption of lower frequency as compared to reference specimens. A significant decrease of the absorbed frequencies was observed depending on the temperature. The largest decrease happened after exposure of samples at 200-300 °C. It indicates that the effect of heat treatment was reduced when the EVA binder was added.

The Corrosion Status of Reinforced Concrete Structure Monitoring by Impact-Echo Method

The paper deals with the study of dominant frequencies of an Impact-Echo method response signal obtained from a reinforced concrete beam with a steel rod diameter of 8 mm. Tension pulse was produced in axis of the rod at one end and detected in axis at opposite end of rod. Dominant frequencies of the response signal will be the main criterions for the reinforced concrete rebar corrosion progress. The article presents the results of measurements obtained after 12 months controlled degradation in aqueous NaCl solution. The results were compared with measurements of electrical resistance of reinforcing steel by using the Thomson double bridge.