Highly efficient crystalline silicon solar cells using a novel shallow angle metallization (SAM) technique

Based on mechanically V-grooved silicon substrates, a novel fine-line mask-free metallization technique-shallow angle metallization (SAM)-has been developed. One SAM method-shallow angle photolithography (SAP)-relies on V-grooved single side photoresist-coated specimen, which is illuminated under a shallow angle perpendicular to the groove direction. In this case the previous groove serves the following one as a shadowing mask. Applying lift-off or metal plating techniques, a fine-line contact grid with a minimum finger width of 10 μm has been obtained without reflection loss due to finger metallization. Details of the optimization of the SAM technique are given. The local point contact and shallow angle evaporation (LOPE) technique is based on the mechanical formation of local openings at the V-groove tops through dielectric layers (SiO₂, and/or Si₃N₄) and the cell emitter followed by a selective and heavy diffusion. The point contacts are interconnected in a subsequent step by metal evaporation under a shallow angle. First results of this simple high efficiency metallization technique are discussed