Detection of power losses in busbar solder contacts by electroluminescence imaging of solar cells

Abstract

Soldered contacts between busbar and interconnected ribbon can be missing or defective due to production or exploitation of solar cells. This causes an increase of total series resistance and thus more power losses in soldered solar cells or whole modules. There are many conventional methods for checking missing solder joints such as optical or mechanical; however they are quite complicated for practical application. We present a new method for quantitative and qualitative checking of the solar cell solder contacts. This method is based on analysis of the line-scan diagrams of the electroluminescence images of a solar cell's area by applying the appropriate voltage between front side and backside. As a theoretical justification we have used the equation for calculation of the electroluminescence emission and the equations for calculation of the voltage distribution and of series resistance in the solar cell's busbar.