Broadband antireflection and hydrophobic CaF2 film prepared with magnetron sputtering

The main aim of the work was to develop an effective antireflective and hydrophobic film, which could have potential application in outdoor environment. Here, a facile magnetron sputtering method was proposed to prepare micro-nano structured CaF2 film on the glass substrate, of which morphology and properties could be controlled with the flow ratio of SF6/Ar during the process of sputtering. The surface of the film was transformed into porous morphology composed of nano-sized particles when the flow ratio of SF6/Ar reached 10%, and the roughness got the maximum value of 144 nm. Moreover, the 10% CaF2 film showed a low refractive index of 1.33–1.31, and the average transmittance in the wavelength range of 300–1100 nm of coated glass was 95.2%. Apart from the broadband antireflective property, 10% CaF2 film also exhibited a lower incidence angle dependence, and the average reflectance remained below 6% as the θ varied from 45° to 90°. Besides, the water contact angle of the film reached 139.4°, demonstrating its good self-cleaning capability. Furthermore, when 10% CaF2 film was used as the cover glass, the short-current density of the solar cell was 5.77, 11.21, and 15.50 mA/cm2, respectively, corresponding to 30°, 60°, and 90° incident angle. Meanwhile, the solar cell’s photoelectric conversion efficiency was as high as 9.13%, 19.35%, and 28.45%, respectively.