Silicon Materials Task Of The Low Cost Solar Array Project Phase Iii Effect Of Impurities And Processing On Silicon Solar Cells Twelfth Quarterly Report

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.