For single-layer antireflection (AR) on glass, a low refractive index (n) AR layer is required to achieve high AR efficiency, which limits the selection of materials. The double-layered AR structure has a lower requirement on materials' n but is typically used for narrow waveband AR, and photovoltaic glass covers require broadband AR to increase the whole-spectrum solar energy transmittance. With the help of a multilayered optical simulation, we optimized the n and thickness of the single and double layered AR structure and found that, for broadband AR, double-layered structure only showed AR efficiency advantages in very high or low top layers' n compared to single AR layer structure. For a n = 1.45 top layer of the double layer structure, the optimized reflectance is 2.57% (single side), while the optimized reflectance of a single AR layer with n = 1.45 is 2.87%, which is a negligible AR efficiency advantage (0.30%) when considering production costs. Moreover, in our experiment, using SiO_2 and SiO_2 and TiO_2 composite layers, the absorption of short wavelengths by TiO_2 ostensibly cancelled this advantage out (92.87% compare to the single layer's 92.98% for single side AR).
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