Fig. 1. (a) Schematic view of the proposed structure. (b) Optical constants of a-Si (180 nm) under different experimental conditions. (c) Optical constants of a-Si in the design. (d) Optical constants of SiO.

Fig. 2. Optical admittance diagrams of the structure without and with the AR layers at 400 nm (first row), 500 nm (second row), and 600 nm (third row). The intersection of the two black dashed lines represents the point (1,0).

Fig. 3. (a) Calculated (red) and measured (blue) reflection spectra of the proposed device at normal incidence. (b) Calculated spectral reflectance curves with (red line) and without (blue line) the AR layers. (c), (d) Illustration of color coordinates calculated from the reflection spectra in (a) on the CIE 1931 chromaticity diagram.

Fig. 4. (a) Absorption spectrum of Ag (black), a-Si (red), and SiO (blue). (b) Absorption spectrum of whole device. (c) Reflection spectra at different incidence angles. (d), (e) Simulated and measured angle-insensitive reflection spectrum. (f) Pictures of the sample observed from different angles.