A Review of Laser Processes Used in Solar Cell Fabrication

Back surface field and laser-fired contacts

The technology which usually used for rear contact passivation in solar cells is that highly doped region near the back contact. This is called back surface field. Normally aluminium is applied to it by evaporation, following by sintering to make aluminium atoms diffuse into the silicon. For reducing the cost per watts generated by solar cell, some different methods were tested for the feasibility analysis.

One of the ways for reducing the cost is doping aluminium locally (Meemongkolkiat et al. 2006). It is obviously that doping less metal could reduce the cost, however the efficiency should not be diminish too much. In this process the oxide on the back surface is partially etched prior to aluminium were screen-printed on it. In their research, with choosing the aluminium screen-printing pastes properly (the composition is not provided in their paper), the efficiency of the solar cells are adequately (16%) compared to the normally full back surface