High-Efficiency Silicon Solar Cells With Boron Doping in the Back Surface Field via Silicon Paste

In this study, silicon (Si) paste formed by 25-wt% p-type Si nanoparticles and 75-wt% organic solvent is used as a boron (B) source. After conducting a laser opening in the back surface, the preprocessed Si wafers are used as the substrate. The Si paste is then screen-printed above the openings. Finally, B atoms diffuse into Si wafers after being cofired with aluminum paste. The voids in rear local contacts are located by scanning acoustic microscopy. The successful B doping is demonstrated by secondary ion mass spectroscopy. Cells with an average efficiency of over 20% are fabricated on China sunergy's production line, especially with a 0.7% improvement of the fill factor values for passivated emitter and rear contact cells.