Photoelectrochemical diffusion length measurements on p-type multicrystalline silicon for industrial quality control

We report on a method based on photoelectrochemistry which allows the measurement of diffusion lengths of multicrystalline silicon before fabricating the photovoltaic device. The results obtained with this method after two years experience on a production line, by the photovoltaic manufacturer Photowatt Int. are presented. It concerns the variation of the diffusion length within the ingots and its correlation with the short-circuit current of the final cells, and the effect of industrial gettering. We also present diffusion length maps on a 10/spl times/10 cm/sup 2/ cell.