Optimization of plasma deposition and etching processes for commercial multicrystalline silicon solar cells

We conducted an investigation of plasma deposition and etching processes on full-size multicrystalline (mc-Si) cells processed in commercial production lines, so that any improvements obtained would be immediately relevant to the PV industry. In one case, we performed a statistically designed multiparameter experiment to determine the optimum PECVD-nitride deposition conditions specific to EFG silicon from ASE Americas, Inc. In a related effort, we studied whether plasma-etching techniques can use standard screen-printed gridlines as etch masks to form self-aligned, patterned-emitter profiles on mc-Si cells from Solarex Corp. Our initial results found a statistically significant improvement of about half an absolute percentage point in cell efficiency when the self-aligned emitter etchback was combined with the PECVD-nitride surface passivation treatment. Additional improvement is expected when the successful bulk passivation treatment is also added to the process.