Surface treatment of high performance multicrystalline silicon wafers

Abstract

This master thesis investigates the properties of high performance multicrystalline silicon, and the production line of black multicrystalline silicon solar cells with PERC architecture. Possible solutions to achieve higher efficiency were explored, and different steps in the production route were examined.

Three steps of the production chain were in focus. Decreasing the polishing time by 70 seconds proved to enhance efficiency. Optimizing the emitter doping process by varying parameters in the deposition step, achieved a more uniform doping distribution across the wafers, and improved overall doping homogeneity by reducing standard deviation by 24%.

Further, the rear passivation step was investigated, and it was found that by increasing the thickness of the Al2O3-layer from 14 to 24 nm, efficiency was improved. The final experiments combined the best result in each of the other steps, and optimized parameters were implemented in the production chain for an overall optimization. A champion efficiency above 20% was achieved, which is 0.23% higher than average baseline efficiency for all PERC wafers investigated in this thesis.