The multi-busbar design : an overview

Abstract

The demand for highly efficient photovoltaic modules at low costs leads to new solar cell designs. For enhanced module efficiency the cell efficiency has to be optimized regarding later operation under module conditions. This implies that the interconnected solar cell structure has to be assessed. Commonly the solar cell itself is optimized separately.In this work an easy to implement cell design was investigated where the number of busbars was varied to decrease the total series resistance of the interconnected solar cell. For this study a simulation program based on the two-diode model was applied to determine the optimal efficiency of the device. Furthermore, the simulations revealed that a device with multiple busbars has a high potential in cost savings due to a reduction in metal consumption for the front side metallization. For an optimized cell structure the amount of Ag paste needed for a sufficient front side metallization could be reduced to 7 mg Ag paste for a 6 inch solar cell. In the same time the efficiency can be increased. A detailed simulation of a screen printed and stringed rear side of a multi-busbar solar cell revealed the amount of rear side pads necessary for a sufficient interconnection leading to low series resistances.