Status and advancement in transferring the laser-fired contact technology to screen-printed silicon solar cells

Silicon solar cells featuring a standard screen-printed front side metallisation as well as a laser-fired contact (LFC) rear side structure were processed on 160 µm thin wafers. The rear structure consists of thermally grown silicon oxide as passivation layer and evaporated aluminium contacted by LFC. On 1 ohm cm FZ silicon efficiencies of up to 18.1 % were achieved. The potential of this cell structure is around 18.9 %. A comparison with the standard Al-BSF cell design shows the high potential of the LFC rear structure. Furthermore, in comparing the cell performance with the one of a very efficient cell structure the different loss mechanisms are pointed out and discussed. Furthermore a simulation on the influence of the back side aluminium metallisation thickness on the solar cell efficiency was performed, indicating that an aluminium layer thickness of 1-2 µm thickness will be sufficient for large solar cells.