Prospects for high efficiency silicon solar cells in thin Czochralski wafers using industrial processes

Lower PV systems cost can be achieved if less silicon material is used in modules and if higher solar cell efficiencies can be achieved cost effectively. In this study the efficiency limits of mass production high efficiency laser grooved buried grid solar cells have been modelled for thinner and thinner wafers. PC1D modelling has been coupled with a 3D ray tracing simulation RAYN to predict cells performance. Given suitable surface passivation, light trapping and minority carrier lifetime, solar cell efficiency can actually increase with decreasing wafer thickness. Cells were made by the RP-PERC process, using thinned industrial grade Czochralski silicon wafers. Cells (4cm2) of over 20% efficiency were fabricated in wafers with a final thickness of 115 µm. Standard production LGBG cells had poor BSFs but on process optimisation nearly 17% efficiency were made in 140 µm micron wafers on an industrial production line.