Optimized grid design for thin film solar panels

• Efficiency gap between cell and panel can be partially compensated by grids.
• Solar panel efficiency of improves up to 17% relative by front contact metallization.
• Modeling gives insight of best design with different boundary conditions.

There is a gap in efficiency between record thin film cells and mass produced thin film solar panels. In this paper we quantify the effect of monolithic integration on power output for various configurations by modeling and present metallization as a way to improve efficiency of solar panels. Grid design and finger dimension optimization was performed monolithically integrated solar panels by modeling under standard conditions and with variation of boundary conditions such as transparent conductor used, conductivity of the metallic pattern and low light intensity. For each, the optimal cell and grid dimensions as well as the power output is presented. In contrast to previous studies that focus on 100 μm wide grid lines, our grid finger width was varied between over a wide range and a finger width of 20 μm was shown to give optimal results. We included mapping the power output for 20 μm, 60 μm and 100 μm wide grid lines as function of cell length, finger spacing and TCO sheet resistance and show that also for wide fingers efficiency improvement of more than 15% is possible. This provides not only optimization of grid dimensions, but also the sensitivity of the power output with respect to the finger dimensions, TCO sheet resistance and the cell length. These results indicate that the application of a grid is a robust solution which allows for a considerable variation (>25%) in the parameter window around the optimum configuration with only small impact (<2%) on the power output.

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