20% efficient screen printed LBSF cell fabricated using UV laser for rear dielectric removal

Low-cost high efficiency solar cells are the key to achieving grid parity with photovoltaic devices. Laser processing in silicon photovoltaics is being incorporated at various stages to achieve this target. This paper details the fabrication, characterization and analysis of 4 cm² screen printed cells with efficiency over 20% achieved using a UV laser ablation for selective opening of rear dielectric. These cells are compared to cells fabricated using a screen printed etching paste for opening vias through the rear dielectric. Microscopy was used to examine the impact of laser pulses on the silicon surface and quality of the BSF and compare it with vias opened using etching paste. Characterization and analysis of these cells is performed using IQE measurements and supported by PC1D modeling. It was found that while laser ablation had an effect on the morphology of the silicon surface, the overall quality of the local back surface field and dielectric rear passivation were maintained, resulting in high cell efficiencies and V_OC.