Optically induced magnetic field of polycrystalline solar cell

Abstract

A laser-SQUID microscope can measure the local magnetic field induced by laser excitation. We obtained four magnetic images over a polycrystalline Si solar cell sample with a needle probe, playing a role as a flux guide from the sample surface to the SQUID, symmetrically shifted in four directions around the laser spot. Then, we converted the photocurrent density image showing the constant background contrast from the measured four magnetic images, although the magnetic images had the gradually inclined contrast due to the top electrode influence. The fine contrast changes corresponding to the defects were clearly observed in the converted current image.