Two-Dimensional Modeling of the Metallization-Induced Recombination Losses of Screen-Printed Solar Cells

摘要

We present an approach of implementing the experimental microscopic observations at metal–Si emitter interface into a 2-D simulation model to investigate the metallization-induced recombination losses of crystalline Si solar cells with firing through metallization. This metal–Si interface is typically characterized by few Ag crystallites grown into Si, whereas the main part of the interface area is covered by a glass layer. By using this simulation model, we were able to disentangle the effect that each of these microscopic features has on solar cell performance. The model assumes the metal–Si interface to be either Ohmic or Schottky, with current extraction occurring only through the direct Ag crystallites–Si interface. The simulation results show negligible degradation in open-circuit voltage () and pseudo-fill factor ( ) if the metal–Si interface comprises the sole presence of Ag crystallites, as long as these crystallites grow only superficially and are not penetrating the p-n junction. A more detrimental effect is observed if the emitter area beneath the glass layer is affected by etching. For more aggressive metallization pastes or for overfiring scenarios where larger in-grown crystallites are observed that are protruding through the p-n junction, the model assuming a Schottky contact qualitatively explains the shunting behavior observed experimentally.