Lock-in thermography - A universal tool for local analysis of solar cells

This contribution gives an overview about the present state of the art of Lock-in Thermography (LIT) applied in solar cell research. Originally introduced as a shunt imaging technique working without light irradiation, recently a number of new LIT techniques have been proposed using light irradiation to the cell. These techniques allow to image the lifetime distribution and Joule heat losses under illumination, and they allow to detect noncontacted regions in the cell. Moreover, shunts can be imaged already before contacts are made. All presently known LIT techniqes applied to solar cells are reviewed and their physical bases are explained. With these new techniques, LIT has become a universal tool for characterizing solar cells.