Lithography-Free Method to Synthesize Quasiperiodic Silicon Inverted-Pyramid Arrays: A Broadband Light Trapper for High-Efficiency Thin Silicon Solar Cells

Thin silicon solar cells can be a low-cost effective photo-conversion device, if the device can efficiently absorb the solar spectrum. Herein, a new lithography-free technique is developed for the fabrication of quasiperiodic silicon inverted-pyramids arrays (SiIPAs), which show a high-light-trapping phenomenon in the ultraviolet–visible—near-infrared (300–2000 nm). Fabricated SiIPA samples show a significant reduction of reflectance (3%) in the silicon absorption band (300–1000 nm). A unique additional absorption of 33–44% compared to the planar silicon is observed in the sub-bandgap region of silicon (1100–2000 nm) for these samples. Photocurrent response measurement confirms the generation of additional electron–hole pairs in the sub-bandgap region of silicon for the SiIPA samples in comparison with planar sample. In these results, the effect of field confinement and the creation of optical resonance modes within these structures, qualitatively supported by numerical simulation, are signified. The estimated short-circuit current density using the experimental absorption spectrum of SiIPAs is 55.46 mA cm⁻², which is far higher than the Lambertian limit of ≈43 mA cm⁻². The theoretical efficiency of the solar cell can be achieved up to 35.22%, which surpasses the Shockley–Queisser limit of 33.7%.