Efficiency enhancement mechanisms in ultra thin silicon solar cells

A possible way today to reduce the costs of solar cells is to make them thinner. Thinner films as active layers means less material and thus less efficiency. A way to keep efficiency comparable to a thick cell is to nanostructure the surface of the thin solar cells. A structured front surface of the solar cell with nanospheres will generally increase the efficiency of the solar cell [1]. In this talk, I will present the basic effects behind the efficiency enhancement in nanostructured ultrathin silicon solar cells. We investigated theoretically solar cell structures textured at the front side with cylinders, spheres and triangles. In case of cylinders and spheres, we found that resonances inside and outside of the nanostructures increase the electric field inside the active material. This can lead to efficiency enhancement. In case of tringle nanostructures, we found chaotic behavior in the simulated system and chaotic wave patterns inside the active layer. I will present in details these resonances and I will show the mechanism of the efficiency increase in the various solar cell configurations. In this investigation, we used different simulation techniques such as ray-techniques, Green function methods and Finite Difference Time Domain simulations.