Progress in the metallisation of n-type multicrystalline silicon solar cells

A study on the optimisation of front contacts of n-type multicrystalline silicon solar cells is presented. In this study the same cell processing was applied to two types of wafers: electronic grade (EG-Si) and metallurgic grade (MG-Si) silicon. The contact firing temperature was optimised, by measuring the contact resistivity of the front and back contacts for different firing temperatures. The front contacts were improved by deposing silver using an electrochemical process. The solar cells were characterised before and after the silver deposition. For all cells processed the line resistance was reduced by over 90% after the silver deposition. After the contact improvement, EG-Si cells showed an absolute efficiency improvement of 2.6%, but MG-Si cells suffered a reduction on the cell efficiency, an effect related to parasitic shunting existent in these cells.

► Optimisation of front contacts in n-type mc-silicon solar cells.
► Performance of electronic (EG) and metallurgic grade (MG) cells compared.
► For both EG and MG cells the optimal contact firing temperature is 850 °C.
► Front contact line resistance is significantly reduced after electroplating.
► Plating process increased EG cells' efficiency and reduced MG cells' efficiency.