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This paper presents a fast light beam induced current technique for the inline control of the final solar cell quality. Based on the use of a galvanometer x-y scanner system, three amplitude-modulated lasers (635 nm and 830 nm) are focalised on the sample surface with a lateral resolution of 60 micro-m on an area of 12x12 cm{2}. The signal generated is collected by an I/V converter and sent to a lock-in amplifier. A series of neutral filters offer the possibility to collect photocurrent maps at different injection level. Appropriate software was developed for the complete automation of the acquisition procedures and for the data analysis. For an inline process monitoring, it was demonstrated that the possibility to use the photocurrent mean value as a good parameter for cell characterization using high resolution maps (600x600 pts) collected in 30 minutes. The statistical study of a significant number of cells shows a clear correlation between photocurrent and quantum efficiency with accuracy below 1%. The mean photocurrent value was then analysed as function of the scanning time (number of points collected). It was demonstrated that even at a high scan speed (3 sec. for a 100x100 cm{2} cell) and low resolution (30x30 pts), the lateral resolution achieved is enough to get a nice correlation between the efficiency losses and the structural defects of the cell.

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Authors: ACCIARRI M ET AL, INF, Department of Materials Science, Milano (IT);AGOSTINELLI, JRC, Environment Institute, Ispra (IT)
Bibliographic Reference: An oral report given at: The 17th European Photovoltaic Solar Energy Conference and Exhibition. Held in: Munich (DE), 22-26 October 2001
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