Increased Front Surface Recombination by Rear-Side Laser Processing on Thin Silicon Solar Cells

We show the degradation of the front surface passivation by rear-side laser processing of thin silicon solar cells when using a laser with a pulse length of 8 ps. 45-μm-thick back-contact back-junction monocrystalline silicon solar cells show an energy conversion efficiency of 18.8% without rear-side laser processing, whereas they show only 7.5% with an additional rear-side laser process step for contact separation. This low efficiency is due to the degradation of the front surface passivation, which is confirmed by quantum efficiency measurements. The internal quantum efficiency at short wavelength is 0.88 without laser processing, whereas it is only 0.33 with the rear-side laser process step.