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Silicon Materials Task of the Low Cost Solar Array Project (Phase III). Effects of Impurities and Processing on Silicon Solar Cells. Phase III Summary and Seventeenth Quarterly Report, Volume 2
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Published: 1980
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DOWNLOAD EBOOK →The object of this phase of the program has been to investigate the effects of various processes, metal contaminants and contaminant-process interactions on the properties of silicon and on the performance of terrestrial silicon solar cells. The study encompassed topics including thermochemical (gettering) treatments, base doping concentration, base doping type (n vs. p), grain boundary-impurity interaction, non-uniformity of impurity distribution, long term effects of impurities, as well as synergic and complexing phenomena. The program approach consists in: (1) the growth of doubly and multiply-doped silicon single crystals containing a baseline boron or phosphorus dopant and specific impurities which produce deep levels in the forbidden band gap; (2) assessment of these crystals by chemical, microstructural, electrical and solar cell tests; (3) correlation of the impurity type and concentration with crystal quality and device performance; and (4) delineation of the role of impurities and processing on subsequent silicon solar cell performance. The overall results reported are based on the assessment of nearly 200 silicon ingots. (WHK).
Silicon Materials Task of the Low Cost Solar Array Project (Phase III). Effect of Impurities and Processing on Silicon Solar Cells. Twelfth Quarterly Report
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Published: 1978
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DOWNLOAD EBOOK →This is the first quarterly report for Phase III of a program to define the effects of impurities, various thermochemical processes and any impurity-process interactions on the performance of terrestrial silicon solar cells. The projected Phase III effort falls in five areas: (1) cell processing studies, (2) completion of the data base and impurity-performance modeling for n-base cells, (3) extension of p-base studies to include contaminants likely to be introduced during silicon production, refining or crystal growth, (4) anisotropy effects, and (5) a preliminary study of the permanence of impurity effects in silicon solar cells. The dominant activity during this quarter was the growth of ingots. Fourteen Czochralski ingots were produced including several base line ingots, p-base ingots for processing studies and large diameter ingots for the anisotropy investigation. Data on cellular breakdown in four of the heavily doped ingots was consistent with prior predictions. Besides the crystal growth a detailed deep level spectroscopic analysis of the electrical activity of Ti in silicon was performed and modeling studies of impurity behavior were extended.
Silicon Materials Task of the Low Cost Solar Array Project (Phase III). Effect of Impurities and Processing on Silicon Solar Cells. Phase III Summary and Seventeenth Quarterly Report, Volume 1
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Published: 1980
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DOWNLOAD EBOOK →The object of Phase III of the program has been to investigate the effects of various processes, metal contaminants and contaminant-process interactions on the performance of terrestrial silicon solar cells. The study encompassed a variety of tasks including: (1) a detailed examination of thermal processing effects, such as HCl and POCl3 gettering on impurity behavior, (2) completion of the data base and modeling for impurities in n-base silicon, (3) extension of the data base on p-type material to include elements likely to be introduced during the production, refining, or crystal growth of silicon, (4) effects on cell performance on anisotropic impurity distributions in large CZ crystals and silicon webs, and (5) a preliminary assessment of the permanence of the impurity effects. Two major topics are treated: methods to measure and evaluate impurity effects in silicon and comprehensive tabulations of data derived during the study. For example, discussions of deep level spectroscopy, detailed dark I-V measurements, recombination lifetime determination, scanned laser photo-response, and conventional solar cell I-V techniques, as well as descriptions of silicon chemical analysis are included. Considerable data are tabulated on the composition, electrical, and solar cell characteristics of impurity-doped silicon.
Silicon Materials Task of the Low-cost Solar Array Project (phase IV)
Silicon Materials Task of the Low-cost Solar Array Project (phase IV)
Solar Energy Update
Silicon Materials Task of the Low Cost Solar Array Project (Phase III). Effects of Impurities and Processing on Silicon Solar Cells. Sixteenth Quarterly Report, July 1979-September 1979
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Published: 1979
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DOWNLOAD EBOOK →The objective of this program is to determine how thermal processes, impurities, and impurity-process interactions affect the properties of silicon and the performance of terrestrial solar cells made from silicon. The Phase III effort encompasses five major topics, several of which represent new directions for our work: (1) examination of the interaction of impurities with processing treatments, (2) generation of a data base and modeling of impurity effects in n-base solar cells, (3) extension of previous p-base studies to include impurities likely to be introduced during silicon production, refining or crystal growth, (4) a consideration of the potential impact of anisotropic (nonuniform) impurity distribution in large Czochralski and ribbon solar cells and, (5) a preliminary investigation of the permanence of impurity effects in silicon solar cells. Important experimental results were obtained in five areas during this past quarter: (1) the impact of HCl gettering on Mo and Ti doped low resistivity silicon was assessed, (2) diffusion profiles were established for Ti and Mo after 1100°C gettering treatments, (3) a correlation was identified between the electrically-active impurity concentration and the metallurgical concentration of several impurities in as-grown ingots, (4) cell and diode measurements verified that no significant anisotropy effects due to Cu or Fe in large diameter CZ ingots, or due to Ti and V in wide silicon web crystals occur, and (5) aging data for Cr indicate a more rapid depreciation in cell performance with time than for Mo or Ti doped cells. A detailed description of the results and analyses of the observed behavior is presented. (WHK).
Silicon Materials Task of the Low Cost Solar Array Project (Phase III)
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Published: 1979
Total Pages:
ISBN-13:
DOWNLOAD EBOOK →The objective of this program is to determine how various processes, impurities, and impurity-process interactions affect the properties of silicon and the performance of terrestrial solar cells made from silicon. The data provide a basis for cost-benefit analysis to the producers and users of Solar Grade Silicon. The Phase III effort encompasses five major topics: (1) examination of the interaction of impurities with processing treatments, (2) generation of a data base and modeling of impurity effects in n-base solar cells, (3) extension of previous p-base studies to include impurities likely to be introduced during silicon production, refining or crystal growth, (4) a consideration of the potential impact of anisotropic (nonuniform) impurity distribution in large Czochralski and ribbon solar cells and, (5) a preliminary investigation of the permanence of impurity effects in silicon solar cells. During this quarter (1) the mechanisms responsible for impurity deactivation during high temperature gettering treatments was examined in detail, (2) the sead to tang and center to edge variation in Czechralski ingot properties for commercial-size ingots doped with Ti and Mn was evaluated, and (3) aging effects in solar cells doped with Ti or Mo were assessed. Also, an analysis of impurity effects on crystal structure breakdown, and the monitoring of ingot lifetimes by photoconductive decay lifetime measurement before and after processing were continued. The highlights of this work are described. (WHK).
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