Large-area honeycomb texturing of Si-solar cells via nanoimprint lithography

The highest solar cell efficiencies on mc-Si were realized using photolithographically defined texturing processes. The feasibility of fabricating honeycomb textures using Nanoimprint Lithography (NIL) was already demonstrated and excellent short-circuit current densities of up to 40.7 mA/cm² were achieved on small-area monocrystalline silicon (c-Si) solar cells. In the present work, large-area honeycomb texturing of multicrystalline silicon (mc-Si) substrates based on Roller-NIL and in-line-capable multi-wafer plasma etching using a modified Roth&Rau SiNA system is demonstrated. The realized honeycomb texture shows superior optical properties compared to isotextured mc-Si reference samples and even random pyramids on c-Si substrates, while surface passivation is comparably good. The fabricated 156 x 156 mm² mc-Si solar cells with Al-BSF show an efficiency of 17.8% compared to 17.3% of the isotextured reference. As VOC remains constant for both textures, the efficiency gain of 0.5% absolute results from a Jsc increase of up to 1.3 mA/cm2 (on cut 50 x 50 mm² cells even 2.5 mA/cm2), which confirms the superior optical quality of the honeycomb texture.