Enhanced forward scattering and transmitted light diffraction in low aspect-ratio Si nanopillars for high efficiency Si solar cells

We investigate optical properties of various aspect-ratio Si nauopillar (Si NP) to find its optimal dimension for enhanced light absorption for thin Si solar cell applications. Two different optical modeling techniques, finite-difference time-domain (TDTD) and rigorous coupled wave analysis (RCWA). are used to analyze the scattering properties of incident light and the diffraction behavior of transmitted light, respectively. From the computational study, we find that a low-aspect ratio Si NP is highly effective compared to high aspect-ratio NPs in terms of forward scattering to suppress light reflection loss from the front surface. In addition, low aspect-ratio NPs also significantly diminishes zeroth (0th) order diffraction and increase the fraction of higher order diffraction which can provide increased light path-length and effective light trapping of the transmitted light. Therefore, a low-aspect ratio Si NP is more ideal for highly enhanced light absorption for thin Si solar cell applications.