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Evaluation of cast mono silicon material for thermal oxide passivated solar cells
We study the impact of material quality on the performance of large area industrial thermal oxide passivated solar cells on cast mono silicon (Si). Cell parameters for cast mono Si materials from three different suppliers and for a boron doped Czochralski (Cz) grown reference Si material are presented. The dislocation density of the cast mono Si material strongly affects open circuit voltage and short circuit current density and thus also cell efficiency. Maximum efficiencies up to 19.8% (243 cm2, as processed) are reached for the wafers with the lowest dislocation density, exceeding the 19.7% conversion efficiency of the Cz-Si reference. Compared to the Cz-Si reference, that shows a 0.5%abs efficiency loss after 24 hours of illumination at 600 W/cm2, the cast mono Si shows only 0.3%abs efficiency loss, although the cast mono wafers feature higher doping compared to the Cz-Si reference wafers. The reduced light induced degradation is presumably due to inherently lower oxygen content of the cast Si material, making this material particularly suited for PERC type cells.