Reflection optimization of a multicrystalline solar cell embedded in a photovoltaic module

Abstract

In this paper we study the surface reflection of a photovoltaic module. The antireflection layer based on silicon nitride SiNx, is deposited by PECVD technique and optimized to a solar cell surface. However, encapsulating the cell in a module (Glass/EVA/SiNx/Silicon) modifies the total reflection of the whole structure. Therefore an optimization of reflection is required to get a good electrical output of the module. In this purpose, we have proceeded by characterizing step by step the optical constants of each layer constituting the module structure: SiNx antireflective layer, EVA layer and glass. We elaborated a specific structure to get those parameters. We measured the total reflection in the UV-VIS-NIR spectra. Reflection curves of EVA and Glass show the same flat shape between 350 and 1100 nm. The mean reflection value of 8.2 % and 7.8 % respectively indicate that the two mediums EVA and glass are quasi similar. Meanwhile the whole structure presents a spectral reflection with a shape similar to that of silicon nitride layer, with a minimum around 600 nm (5.1 % and 2.3 % respectively). After simulating the optical parameters of the layers, we optimized again the reflection of the structure to be minimal. This indicates us that the optimal values of the SiNx layer to be used in the structure are: n = 2.4 and d = 69.18 nm. These values give a minimum reflection of the structure around 0.16 % at 614 nm.