The Origin Of Reduced Fill Factors Of Emitter-wrap-through-solar Cells

摘要

Low fill factors generally limit the efficiency of emitter-wrap-through (EWT) solar cells. Until now, a conventional series resistance limitation along the laser-drilled EWT vias has usually been assumed to be responsible for this effect. We demonstrate that the characteristic fill factor loss is caused by a crucial change in the diffusion currents inside the base,rnwhich are influenced by the conductivity along the laser-drilled EWT vias. In addition, we show that the EWT via conductivity influences the fill factor loss caused by an iron contaminated base. This result affects the proposition that the EWT design is suitable for multicrystalline silicon in which interstitial iron is known to be the main contaminant.