Nano-structuring the surfaces of solar cells presents the opportunity to engineer the optical response with more degrees of freedom than using only flat layers. Particularly, it allows to exploit diffraction effects not present in conventional antireflective coatings (ARCs) based on destructive interference [1] and gradual index matching [2]. Diffraction does not occur if the grating period is smaller than the light wavelength. But the wavelength is much shorter inside the solar cell than in air or glass, thus by placing the grating at an interface with a high refractive index contrast, and choosing the grating period to be slightly smaller than the shortest wavelength of interest, all the light diffracted by the grating (by addition of a reciprocal lattice wave-vector) propagates forward into the solar cell, reducing reflection [3,4]. The intensity of the effect depends on the scattering efficiency of the grating, which in turn depends on the refractive index contrast, among other factors. A viable approach to overcome the difficulty of finding materials with the appropriate refractive indexes is based on porous or mixed layers, but the maximum usable refractive index is still limited by the choice of materials with low absorption in the wavelength range of interest.

Trabajo presentado en el 13th International Conference on Concentrator Photovoltaics (CPV-13), celebrado en Ottawa (Canadá), del 1 al 3 de mayo de 2017

We acknowledge financial support by MINECO (TEC2015-64189-C3-2-R) and CAM (S2013/MAE-2780).

Peer reviewed