ECN publication
Local carrier lifetime of non-passivated multi-crystallinesilicon wafers measured by the MFCA method
Published by: Publication date:
ECN 1995
ECN report number: Document type:
ECN-RX--95-060 Other
Number of pages: Full text:
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Contactless measurement techniques of excess carrier recombinationbehaviour in semiconductors are well known. The methods were applied to characterise multi-crystalline silicon ingots or multi-crystalline wafers with passivated surfaces. In the first case the material is thick enough to neglect the influence of the surfaces, in the second case the surfaces can be ignored because they are passivated. In this paper we will show that the Modulated Free Carrier Absorption (MFCA) method can be used to measure the local bulk lifetime of as-cut wafers without surface passivation techniques. The wafer can be characterised directly at the input of a solar cell manufacturing process without any treatments as for example a thermal oxide passivation technique, which might alter the excess carrier recombination in the bulk because of the temperature. Certainly this technique cannot be applied in all cases, but by an uncertainty analysis it is shown that it yields valuable information in most cases that are relevant to multi-crystalline solar cell production. By different examples the results of this characterisation technique are shown and a correlation between mean carrier lifetime in the as-cut wafer and the final solar cell parameters is demonstrated. 7 figs., 11 refs.

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