Laser processing for back-contacted silicon solar cells

Abstract

We use laser ablation of Si and laser ablation of organic coatings on Si wafers for locally processing solar cells. We present experimental investigations of a variety of pulsed lasers, such as Nd:YAG laser and frequency-converted solid state lasers concerning their applicability of laser structuring silicon solar cells. The laser-induced Si crystal damage is investigated by means of contact-less minority carrier lifetime measurements. With our optimized laser parameters for structuring monocristalline Si we find the depth of the laser-induced damage to be 3 µm for the frequency-tripled (λ = 355 nm), 4 µm for the frequency-doubled (λ = 532 nm), and above 20 µm for the Nd:YAG (λ = 1064 nm) laser. One-dimensional simulation results show the influence of a lowered minority carrier lifetime in the silicon absorber on the performance of a back junction solar cell. With an optimized laser process we fabricate solar cells with a Rear Interdigitated contact scheme that is metallized by one Single vacuum Evaporation step (RISE). The so-called RISE process aims at highest efficiencies in combination with low process complexity.We use laser ablation of Si and laser ablation of organic coatings on Si wafers for locally processing solar cells. We present experimental investigations of a variety of pulsed lasers, such as Nd:YAG laser and frequency-converted solid state lasers concerning their applicability of laser structuring silicon solar cells. The laser-induced Si crystal damage is investigated by means of contact-less minority carrier lifetime measurements. With our optimized laser parameters for structuring monocristalline Si we find the depth of the laser-induced damage to be 3 µm for the frequency-tripled (λ = 355 nm), 4 µm for the frequency-doubled (λ = 532 nm), and above 20 µm for the Nd:YAG (λ = 1064 nm) laser. One-dimensional simulation results show the influence of a lowered minority carrier lifetime in the silicon absorber on the performance of a back junction solar cell. With an optimized laser process we fabricate solar cells with a Rear Interdigitated contact scheme that is metallized by one Single vacuum Evaporati...