In this paper we demonstrate the parallel application of light beam induced current (LBIC)and lock-in infrared thermography for the investigation of strong shunting regions inmulticrystalline silicon solar cells. Usually both mappings are not correlated, but in thiscase the shunts could be imaged by both techniques. If for a locally generated photocurrentthe conductance through a shunt lying nearby is comparable to that across the emitter intothe current amplifier, local shunts become visible in the LBIC as dark regions. After therear contact of the cell was removed, the LBIC technique was performed fromthe rear side of the cell. The images point to the existence of inversion layersalong grain boundaries crossing the bulk of the cell. Obviously, these inversionlayers represent the dominant material-induced shunt type in multicrystallinesilicon solar cells. Moreover, it has been shown that cracks may lead to shunts.