Influence of a shunt on the electrical behavior in thin film photovoltaic modules – A 2D finite element simulation study

•We simulated the electrical properties of thin film modules by using a 2D FEM model.•We investigated the effect of a shunt onto the electrical module performance.•The shunt position affects the module performance.•The shunt current makes detours over neighboring cells.•Shunts induce lateral “circular” currents in all cell electrodes in the module.

Despite significant efficiency improvements of thin film photovoltaic modules over the last years, this technology struggles with the same problem – shunts that lower the output power dramatically. In this work, we studied the influence of a single shunt on the module performance by electrical 2D finite element simulations. By varying parameters such as irradiance, shunt resistance, shunt position and shunt size a profound understanding of the shunt’s impact on the module performance was achieved. Most remarkable is the dependence of the module’s output performance on the local shunt position, which can make up to 25% of the losses. Such high losses are caused by “circular” lateral currents in the electrode layers that spread in the shunted as well as into the neighboring cells. We show that the shunt’s position inside the cell determines the geometry of the lateral currents and, consequently, the shunt’s influence region.The finite element model presented here was developed on the basis of CIGS thin film modules, but the results are qualitatively valid for other monolithically series connected thin film module technologies like CdTe or a-Si:H.

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