Computational analysis of crack opening in photovoltaic solar cells in the presence of multiple interacting cracks

The influence of complex fracture patterns on the Silicon-based photovoltaic (PV) solar cells is investigated. Fracture patterns in solar cells are reported to generate electrically insulated areas in solar cells. Previous studies on cyclic bending tests performed on PV modules composed by solar cells arranged in two rows and encapsulated into polymer have shown the progress of crack growth with the number of applied loading cycles. From these tests, the fracture patterns after a certain number of cycles are identified based on the electroluminescence (EL) images. In this study, computational analysis is performed to assess the level of crack opening of multiple crack patterns, which has been assumed to be the major source for the increased local electrical resistance of cracks. To this aim, a solar cell after 350 cycles along with its fracture pattern and the corresponding boundary conditions are selected for the computational investigation. A solid-shell based computational model combined with the phantom node method (PNM) is herein employed to simulate cracks in Silicon. A hybrid solid-shell finite element is adopted for the continuum discretization. Discontinuity across the crack surfaces is modelled using the phantom node method. Crack opening displacements in the deformed configuration of the selected cracks around the observed electrically inactive area are plotted versus the normalised position. The opening displacements of the cracks close to the insulated area are observed to reach the maximum value, much higher than for the other cracks, supporting the assumption that crack opening is a major quantity to be investigated for electrical power-loss predictions.