The application of double-layer silicon nitride films on the solar cell anti-reflection coatings

In this paper, reflectance features, external quantum efficiency, and energy conversion efficiency of mono-crystalline silicon solar cells with double-layer silicon nitride (SiNx) anti-reflection coatings were investigated. The simulated results by the PC1D software showed that the combination in which the bottom SiNx layer had a thickness of 35 nm and refractive index of 2.3, the upper layer had a thickness of 40 nm and refractive index of 1.9 achieved a minimum reflectance. Double-layer SiNx anti-reflection coatings were fabricated by adjusting the ratio of SiH4:NH3 in the PECVD growth. The measurement showed that the double-layer coatings had less reflectance than the single-layer coatings in short wavelength, while they did not show obvious changes in the range of 380 nm to 400 nm for the intensive absorption. Although the combination parameters were not optimum, the energy conversion efficiency of the double-layer SiNx anti-reflection coatings solar cell was improved from 17.88% to 18.03% comparing with the single-layer coatings.