Fabrication of antireflective nanostructures for crystalline silicon solar cells by reactive ion etching

In this study we have fabricated large-area (15 × 15 cm²) subwavelength antireflection structure on poly-Si substrates to reduce their solar reflectivity. A reactive ion etching system was used to fabricate nanostructures on the poly-silicon surface. Reactive gases, composed of chlorine (Cl₂), sulfur hexafluoride (SF₆) and oxygen (O ₂), were activated to fabricate nanoscale pyramids by RF plasma. The poly-Si substrates were etched in various gas compositions for 6-10 min to form nano-pyramids. The sizes of pyramids were about 200-300 nm in heights and about 100 nm in width. Besides the nanoscale features, the high pyramid density on the poly-Si surface is another important factor to reduce the reflectivity. Low-reflectivity surface was fabricated with reflectivity significantly reduced down to < 2% for photons in a wavelength range of 500-900 nm.