A new approach: low cost masking material and efficient copper metallization for higher efficiency silicon solar cells

A new approach based on the development of a new low-cost masking material and a new technique for performing fast wet processes (i. e. chemical etching and electroplating processes) are presented, back side silver removal is proposed allowing in combination with a multi-bus bar module assembly technique to boost standard silicon solar cells towards higher efficiencies at low cost. The new masking material based on a low-cost wax is able to withstand wet hot chemical treatment up to 100 degrees C. The developed wax composition that costs 10 times less than photoresist can be taken into consideration as an industrial masking process for solar cell for the front copper metallization process. However, the industrial applicability of the copper plating processes foresees several issues concerning the cell throughput for the plating technique at industrial level, which is directly connected to the plating speed. In this work, it is shown how using the new concept of coalescent dynamic liquid drop/meniscus is possible to plate 35 mu m thick copper fingers on wax masked solar cell with a deposition speed as high as 1 mu m/s. Combining the proposed technique with the back side selective plating, a silver-free silicon solar cell fabrication process is developed allowing to reach efficiencies higher than 18 % for monocrystalline silicon solar cell.