Analysis of the Effects of Impurities in Silicon. Second Quarterly Report, May 1-July 31, 1979

摘要

The purpose of this program is to conduct a solar cell fabrication and analysis program to determine the effects on the resultant solar cell efficiency of impurities intentionally incorporated into silicon. The program will employ flight-quality technologies and quality assurance to assure that variations in cell performance are due to the impurities incorporated in the silicon. Efforts included (1) completion of the processing of verification cells to assure proper process control and to serve as a data base for all future experimental work, (2) study of the dependance of cell performance on crystal orientation to aid in evaluation of the 111 test wafers and (3) completion of the first 5 test runs and analysis of their performance. The verification runs resulted in an average AMO cell efficiency of 12.9% at 25 exp 0 C (in excess of 15% AMI at 25 exp 0 C). The average test lot efficiency has varied from 10.6 to 12% at AMO and 25 exp 0 C. The first 5 test lots have shown a large variation in bulk resistivity (0.2 omega -cm up to 3.8 omega -cm) resulting in large variations in lot open circuit voltage (561 mV to 610mV) as would be expected for doping with any active species. The presence of grains boundaries in several wafers had no effect on cell electrical performance. All monitor and control runs to date have cell performance characteristics indistinguishable from the verification runs indicating no contamination. The type and level of impurity doping in each test lot is given and the mechanism responsible for the degradation of cell performance has been identified and correlated to the doped impurities. (ERA citation 05:013277)