Rear-side point-contacts by inline thermal evaporation of aluminum

This paper presents a detailed analysis of point-contacted aluminum rear-sides for silicon solar cells that are metalized by inline thermal evaporation. We deposit aluminum layers of 2 μm thickness at dynamic deposition rates of 1.0, 2.9 and 5.0 μm*m/min on partially laser ablated a-Si / SiN passivation layers. The specific contact resistance of aluminum to p-type silicon with a doping density of 1×10¹⁶ cm^-3 is determined to be 7.4 ± 1.2 mΩcm². Using the dynamic infrared lifetime mapping technique we measure effective lifetimes on the metalized samples of 300 cm/s at a metallization fraction of 3%. Simulations show a relative improvement of energy conversion efficiency of 0.6% over silicon solar cells featuring a screen printed aluminum rear-side metallization.