Ray tracing of inverted pyramids for light-trapping in thin crystalline silicon for solar cells

In this work, ray tracing of inverted pyramids is conducted to investigate different light-trapping schemes in thin crystalline silicon (c-Si) for solar cells. Monocrystalline silicon (mono c-Si) wafer with thickness of 30 μm is used as the substrate. The light-trapping schemes include front inverted pyramids (Scheme I), rear inverted pyramids (Scheme II) and inverted pyramids on both sides of the c-Si (Scheme III). Each light-trapping scheme is equipped with a front silicon nitride (SiNx) anti-reflective coating (ARC). Planar c-Si is used as a reference. The light-trapping performance is investigated within 300-1200 nm wavelength region, utilizing AM1.5 G solar spectrum at normal incidence as the illumination. From the absorption profile, the maximum potential short-circuit current density (Jmax) is calculated throughout the entire region, assuming unity carrier collection. Planar c-Si exhibits Jmax of 22.5 mA/cm2. Light-trapping with Scheme I demonstrates the highest broadband light absorption, owing to superior light scattering by the front pyramids and effective light-coupling by the SiNx ARC. This results in Jmax of 39.1 mA/cm2, which corresponds to 74% enhancement when compared to the planar c-Si reference. The findings from this work demonstrate the potential of the thin c-Si as a promising PV technology for the future.