5.1. Antireflection coating (ARC)
As discussed above, ARC is used to reduce the reflection from the front surface. This reduction is based on the destructive interference at the interface [29] and [30]. It consists of a layer of a dielectric material deposited on the surface of the active material of solar cell having a particular thickness. This layer should be transparent and is a quarter wavelength thick (thickness, d=λ/4n, where n is refractive index). The light wave reflected from the antireflection coating is 180° out of phase with the reflected wave from the semiconductor surface. This causes destructive interference, resulting in zero net reflected energy [31].
The refractive index of ARC should be between the materials on either side. Glass and Si have refractive index of 1.5 and 3.7 and for minimum reflection antireflection coating should have refractive index of ~2.4. Structure with ARC is shown in Fig. 6[32] and [33].