Optimization-based design of surface textures for thin-film Si solar cells Citation

We numerically investigate the light-absorption behavior of thinfilm silicon for normal-incident light, using surface textures to enhance absorption. We consider a variety of texture designs, such as simple periodic gratings and commercial random textures, and examine arbitrary irregular periodic textures designed by multi-parameter optimization. Deep and high-index-contrast textures exhibit strong anisotropic scattering that is outside the regime of validity of the Lambertian models commonly used to describe texture-induced absorption enhancement for normal incidence. Over a 900–1100 nm wavelength range, our optimized surface texture in two dimensions (2D) enhances absorption by a factor of 2.7πn, considerably larger than the original πn Lambertian result and exceeding by almost 50% a recent generalization of Lambertian model for periodic structures in finite spectral range. 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