Computer Simulation of the Reflection Coefficient of Protective Coatings of Mirrors of Solar Devices
Abstract
In solar technology mirrors are used with an outer and rear coating of a reflective layer. The reflection coefficient of mirrors with an external coating is greater than that of mirrors with a rear coating, but over time it decreases due to the destructive effects of the external environment. Therefore, solar technology began to apply mirrors with an external coating and a protective film to protect them from the effects of the external environment. The paper presents the results of computer simulation of protective films for aluminum mirrors. It is shown that dielectric films with a refractive index from 1.38 to 1.8 have practically no effect on the reflectance of an aluminum mirror if their thickness does not exceed 15 nm. To protect the surface of an aluminum mirror, SiO2 + Al and ZnS + MgF2 mixed films with a thickness from 10 to 15 nm with a SiO2 and ZnS concentration of 10% are recommended. Of interest is a MgF2 + ZnS film with a MgF2 concentration of 43% and a thickness of 10–15 nm. The film reduces the reflection coefficient of the mirror by no more than 2% and has no internal stresses.