Understanding the Movement of Cracked Solar Cell Parts in PV-modules during Mechanical Loading

Abstract

We measure the three dimensional movement of cracked solar cell parts in standard sized PV-modules during a four line bending test. We develop a model which explains this movement assuming that the centers of mass of the solar cells or cell parts are fixed to the module glass. The widening of all cell gap widths is proportional to the bending roll displacement until a cell cracks in parallel to the bending rolls due to the tensile stress in the cells. At this point, the crack opens abruptly while the two parallel cell gaps next to the cracked cell close simultaneously by the same distance in sum. From here on, the cell gaps and the cell crack increases proportionally to the bending roll displacement. Since the distance between the centers of mass of both cracked cell parts is independent of the crack position, the crack width is also independent of the crack position for single cracks. Multiple parallel cracks in solar cells have smaller crack widths according to this model. Laminates without a backsheet show about 30% larger crack widths.