Experimental optimization of solar cells edge junction passivation

We have developed in this study a simple procedure to determine the optimal etching time to passivate the parasitic edge junction of solar cells. The principle of the technique is based on the control of cells electrical characteristics evolution during the gradual elimination of this edge junction. Using plasma technique, the experiments were conducted on monocrystalline and multicrystalline 4in silicon solar cells round and square in shape respectively. For monocrystalline silicon, the edge junction etch rates of 55.5nm/min and 90.0–96.5nm/min has been found for a batch of 20 cells with chemically phosphorus silica glass (PSG) etched and non-etched respectively. The deduced selectivity S=Si/PSG is about 10. For a batch of 100 multicrystalline silicon solar cells, 34min were sufficient to remove 0.4μm parasitic junction depth. For the three batches, the difference between the etch rates is explained by the phosphorus concentration and silicon loading effect. As well as for etching uniformities, they are considered good to acceptable.