Two step Ni/Cu metallization for commercial c-Si solar cells: 1 to 10 suns

A new metallization scheme as an alternative to screen printed metallization for crystalline Si (c-Si) solar cells is studied with an objective to reduce the series resistance. The reduction in series resistance of solar cells results in an improved efficiency at one-sun as well as at low concentration levels (less than 10 suns). Commercially processed c-Si solar cells without front contacts are used as a starting point. A new technique of polymer sheet masking and laser engraving is used to open the Si_xN_y antireflective coating (ARC) followed by two step metallization consisting of electrodeposited Ni and Cu for the front contact. The deposited Ni layer on Si substrate is then annealed (to obtain nickel silicide (NiSi)). This is followed by Cu electroplating on the silicide layer. An optimum temperature and time for Ni annealing to obtain NiSi is investigated based on the solar cells parameters such as η, I_sc, V_oc and FF at one sun. It is observed that the optimum result of the solar cell is obtained for annealing temperature 420°C with efficiency levels within 13-14%. These solar cells are then used to fabricate a low concentrator c-Si solar cell whose performance is tested between the concentration levels of two to four suns..