Simulation of optical properties of Si wire cells

Abstract

We solve the Maxwell equations to quantify the amount of photo-generation in Si solar cells consisting of arrays of wires instead of bulk thin-films. Published transmission and reflectance measurements suggest that an array of Si wires absorbs sunlight very effectively due to strong diffraction and scattering. However, a detailed theoretical understanding and quantification of the actual photo-generation is only in its initial stage. In our simulations, the geometrical parameters of the wires are synthesized by means of cluster simulations. Applying the finite element method, we are able to compute randomly aligned wires within manageable time limits and affordable computer capacity. We show that Si wires have strong photonic properties. For example, our simulations surpass the Lambertian limit (for isotropically incident light) at λ = 1000 nm, as has been reported in many experiments.