Results of the Lifetime Round Robins Done in the Framework of the Semi M6 Solar Silicon Standardization Task Force

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Abstract
In the framework SEMI standardization activities the SEMI M6-85 “Specification for Silicon Wafers for Use in Photovoltaic Solar Cells” is revised by an European task force. After more than four decades of silicon solar cell development there is still no reliable and strong correlation between the achievable cell efficiency and the electronic bulk material of unprocessed silicon wafers. The minority carrier lifetime of unprocessed bulk material is considered to have the potential to deliver this correlation. Therefore, similar to solar cell efficiency measurements, an easily applicable, instrument independent measurement for minority carrier lifetime under realistic photovoltaic conditions is desirable. Four lifetime round robins were finished until now and a fifth one is going on at the moment. Many lessons, like how to perform these round robins, what are the sample characteristics, what is the influence of measurement conditions and surface passivation, were learned. But although there is a steady progress in defining more accurate measurement and sample preparation conditions, there is still no general carrier lifetime measurement procedure available that could be used in the above mentioned standard.