Optical Properties of CaF2 Thin Film Deposited on Borosilicate Glass and Its Electrical Performance in PV Module Applications

Calcium fluoride (CaF2) is deposited via vacuum thermal evaporation on borosilicate glass to produce an anti-reflection coating for use in solar modules. Macleod’s essential simulation is used to optimize the thickness of the CaF2 coating on the glass. Experimentally, a 120 ± 4 nm-thin CaF2 film on glass shows an average increase of ~4% in transmittance and a decrease of ~3.2% in reflectance, respectively, when compared to that of uncoated glass (Un CG), within the wavelength spectrum of approximately 350 to 1100 nm. The electrical PV performance of CaF2-coated glass (CaF2-CG) was analyzed for conventional and lightweight photovoltaic module applications. An improvement in the short-circuit current (Jsc) from 38.13 to 39.07 mA/cm2 and an increase of 2.40% in the efficiency (η) was obtained when CaF2-CG glass was used instead of Un CG in a conventional module. Furthermore, Jsc enhancement from 35.63 to 36.44 mA/cm2 and η improvement of 2.32% was observed when a very thin CaF2-CG was placed between the polymethyl methacrylate (PMMA) and solar cell in a lightweight module.