Interactions Of Structural Defects With Metallic Impurities In Multicrystalline Silicon

Interactions between structural defects and metallic impurities were studied in multicrystalline silicon for solar cells applications. The objective was to gain insight into the relationship between solar cell processing, metallic impurity behavior and the resultant effect on material/device performance. With an intense synchrotron x-ray source, high sensitivity x-ray fluorescence measurements were utilized to determine impurity distributions with a spatial resolution of {approx} 1{micro}m. Diffusion length mapping and final solar cell characteristics gauged material/device performance. The materials were tested in both the as-grown state and after full solar cell processing. Iron and nickel metal impurities were located at structural defects in as-grown material, while after solar cell processing, both impurities were still observed in low performance regions. These results indicate that multicrystalline silicon solar cell performance is directly related to metal impurities which are not completely removed during typical processing treatments. A discussion of possible mechanisms for this incomplete removal is presented

Interactions of structural defects with metallic impurities in multicrystalline silicon

Interactions between structural defects and metallic impurities were studied in multicrystalline silicon for solar cells applications. The objective was to gain insight into the relationship between solar cell processing, metallic impurity behavior and the resultant effect on material/device performance. With an intense synchrotron x-ray source, high sensitivity x-ray fluorescence measurements were utilized to determine impurity distributions with a spatial resolution of {approx} 1{micro}m. Diffusion length mapping and final solar cell characteristics gauged material/device performance. The materials were tested in both the as-grown state and after full solar cell processing. Iron and nickel metal impurities were located at structural defects in as-grown material, while after solar cell processing, both impurities were still observed in low performance regions. These results indicate that multicrystalline silicon solar cell performance is directly related to metal impurities which are not completely removed during typical processing treatments. A discussion of possible mechanisms for this incomplete removal is presented

Stress studies in EFG. Quarterly progress report, October 1-December 31, 1983

Stress analysis at Harvard University has examined the implication of non-zero interface stresses on model predictions. Stress distributions at distances greater than about 1 mm from the interface are shown to be independent of the interface stress at high creep intensities, and the predictions based on zero initial stress can be used with confidence. Numerical models for growth dynamics developed at MIT are compared with experimental data on t-V relationships and on interface shape obtained from impurity redistribution in aluminum-doped 10 cm wide ribbon. Comparison of primary creep responses in FZ (floating zone) and CZ (Czochralski) silicon above 1200/sup 0/C using four-point bending indicates that oxygen has a significant influence on the creep rate. Both the strain rate and resulting dislocation densities generated in FZ silicon are an order of magnitude higher than for the CZ material at comparable applied stress levels. A fiber optics probe suitable for temperature measurement during sheet growth has been constructed and tested. Study of the feasibility of using laser interferometric techniques for residual stress measurements has continued at the University of Illinois. The method has been successfully applied to CZ silicon, and is being evaluated for use with EFG ribbon

Review on ribbon silicon techniques for cost reduction in PV

The shortage of Si feedstock and the goal of reducing Wp costs in photovoltaics (PV) is the driving force to look for alternatives to ingot grown multicrystalline (me) Si wafers which have the highest share in the PV market. Ribbon Si seems to be a very promising candidate as no kerf losses occur, resulting in reduced Si costs per Wp. In addition, there is no need for the energy consuming crystallization of the ingot and therefore energy payback times can be significantly reduced. The higher defect density in ribbon Si materials has to be taken into account during cell processing, but ribbon materials already commercially available show excellent efficiencies, while for the most promising techniques efficiencies are significantly lower, but very promising. In this presentation an overview of ribbon Si technologies currently under research will be given, based on available data on crystal growth as well as solar cell processing and cell Parameters

Atrial fibrillation history impact on catheter ablation outcome. Findings from the ESC-EHRA Atrial Fibrillation Ablation Long-Term Registry

Background Atrial fibrillation (AF) promotes atrial remodeling that in turn promotes AF perpetuation. The aim of our study is to investigate the impact of AF history length on 1-year outcome of AF catheter ablation in a cohort of patients enrolled in the Atrial Fibrillation Ablation Registry. Methods We described the real-life clinical epidemiology, therapeutic strategies, and the short- and mid-term outcomes of 1948 patients (71.9% with paroxysmal AF) undergoing AF ablation procedures, stratified according to AF history duration (= 2 years). Results The mean AF history duration was 46.2 +/- 57.4 months, 592 patients had an AF history duration = 2 years (mean 75.5 +/- 63.5 months) (P = 2 years (34.0%) (P = 0.037). AF history duration >= 2 years, overall ablation procedure duration, hypertension, and chronic kidney disease were all predictors of recurrences after the blanking period. Conclusions In this multicenter registry, performing catheter ablation in patients with an AF history >= 2 years was associated with higher rates of AF recurrences at 1 year. Since cumulative time in AF in not necessarily equivalent to AF history, its role remains to be clarified.Cardiolog