Spatial and directional distribution of cracks in silicon PV modules after uniform mechanical loads

Abstract

Crystalline silicon photovoltaic (PV) modules are prone to the formation of cracks in the solar cells when subjected to mechanical loads. In extreme cases these cracks lead to an electrical separation of cell parts, thus reducing the power output of the module. We present the analysis of crack distributions in PV modules after being subjected to a uniform mechanical load. A simplified numerical simulation of the strain distribution shows a good agreement with experimentally observed preferred cracking directions in PV modules. The simulation allows for the explanation of position-dependent cracking directions in terms of a principal strain analysis. Cracks parallel to the busbars may lead to exceptionally large cell parts being separated. Such cracks are predicted to occur more often than less critical cracks in other directions. Furthermore, we present a statistical analysis of the spatial and directional distribution of cracks from 27 PV modules with 60 cells each. The PV modules have aluminum frames and were loaded uniformly. In agreement with the numerical analysis we find, that the predominant crack orientation is parallel to the busbar with 50% of the cracked cells. However, cells in the corners of the modules are found to crack diagonally, which can be understood using the numerical strain analysis. We propose how to reduce the potential risk of cracks and thus to avoid the subsequent reduction of the module power.