Can Luminescence Imaging Replace Lock-in Thermography on Solar Cells?

The purpose of this paper is a detailed comparison of selected luminescence and lock-in thermography (LIT) results on one exemplary sample and the drawing of corresponding conclusions. Our focus is on solar cells, but some investigations on wafers will be discussed as well. The comparison will help to decide which characterization tools are needed to solve technological problems. It will be demonstrated that luminescence imaging may widely replace LIT with respect to the analysis of recombination-active bulk defects, cracks, series resistance, and junction breakdown sites. However, some important investigations can be done only by LIT. LIT allows for a quantitative analysis of different kinds of leakage currents both under forward and under reverse bias, enabling a reliable analysis of local I-V characteristics. It is shown that LIT and luminescence imaging are complementary to each other and should be used in combination.