Fig. 1. Illustration of reflectance suppression achieved by a metasurface-based silicon antireflective coating, composed of cross-circle meta-atoms, demonstrating approximately an order of magnitude improvement compared with an unstructured silicon solar cell.

Fig. 2. Schematic depiction of the studied setup: (a) ARC as a single layer of Si etched on Si. (b) Hybrid meta-atom that is a superposition of a rectangular cross and cylindrical post geometries. The geometric parameters are the circle radius (R), cross arm width and length (W and L, respectively), height (H), and unit cell period (P).

Fig. 3. Reflectance maps for the cross-circle geometry showed in (a) with R=90nm, W=60nm, L=300nm, H=150nm, and P=380nm, for (b) TE and (c) TM polarized plane waves as a function of incident wavelength and incident angle.

Fig. 4. Reflectance maps for the free-form geometry showed in (a) for (b) TE and (c) TM polarized plane waves as a function of incident wavelength and incident angle.

Fig. 5. Reflectance spectra of the bare silicon substrate (light gray), single-layer antireflective Si3N4 80 nm coating (black), optimal cross-circle (red), and free-form (blue) periodic 150 nm thick arrays under (a) normal incidence and (b) 30 deg oblique incidence. The dashed horizontal line marks reflectance level of 5%. The shaded region marks the AM1.5 solar spectrum.

Fig. 6. (a) and (c) Reflectance boosting factor, ηR [see Eq. (2)] and (b) and (d) power transfer boosting factor PT [see Eq. (3)], averaged over the wavelength and incident angle, respectively, for the single-layer antireflective Si3N4 80 nm coating (black), optimal cross-circle (red), and free-from (blue) periodic 150-nm thick arrays.

Fig. 7. Field profiles for the normally incident 580 nm plane wave for (a) cross-circle and (b) free-form designs.