LBIC and Reflectance Mapping of Multicrystalline Si Solar Cells

Multicrystalline silicon (mc-Si) is increasingly used in the photovoltaic industry. However, this material is characterized by intrinsic structural heterogeneities (dislocations, grain boundaries, etc.), which are detrimental to the performance of the cells. The minority-carrier diffusion length is sensitive to these defects, and gives an indication of the material quality and its suitability for solar cell use. The laser beam induced current (LBIC) technique makes it possible to estimate the local minority-carrier diffusion length from photocurrent contrast data. The purpose of this work is to show an advanced homemade LBIC system that highlights the importance of controlling the laser power excitation and the reflected light in inhomogeneous mc-Si samples. This control demonstrates that the estimated minority-carrier diffusion length (L (Diff)) in texturized multicrystalline wafers strongly depends on the collecting conditions of the reflected light.