Novel front metal contact patterning scheme for C-SI solar cells

An alternative metallization scheme for c-Si solar cells other than Ag screen printing, has gained importance in recent years. Metallization techniques such as two step electroplated contacts of Ni/Cu and Ni/Ag, have shown higher efficiencies in c-Si solar cells. One of the important processes in the electroplated contacts is opening of the dielectric layer (like SiN_x or SiO₂). In this paper a novel contact patterning scheme based on use of a thermally sensitive chemical etching paste Merck, IsishapeTM is presented. Commercially processed c-Si solar cells of area 4 × 4 cm² are used in the experiment. These solar cells are processed for texturization, p-n junction formation, antireflective coating (ARC) deposition and back surface field (BSF), but without front metal contacts. A thermally sensitive paste from Merck, Isishape^TM is used for etching the ARC. A block of stainless steel is micro-machined in order to get extrusion of metal pattern similar to finger and bus bar for the front metal contact. Arrangements for electrical heating of the metal block are made. Using the electrical heaters the metal block can be heated up to 500°C. Using the proposed technique finger lines of width 250 μm are developed on the ARC coated textured c-Si wafers. The proposed patterning technique can be used in industrial environment with high throughput.