This analysis presented the light reflection loss about 2 % with the optimum nano- gratings having height of *300 nm and period of *830 nm, which is *28 % lower than that of flat type substrates. The light reflection was calculated using the FDTD method. The simulated results show that the light reflection of a rectangular shaped grating structure is *30 %, however, the light reflection becomes *2 % for a triangular (conical or perfect cone) shaped nano-grating structure, because the refractive index changes gradually in several steps and reduces the light reflection. It is also noticed that for the intermediate structures (such as, trape- zoidal and parabolic shaped nano-gratings), the light reflection is lower than the rectangular shaped nano-grating structure but higher than the triangular shaped nano-grating structure. The simulated results confirm that the reduction of light reflection in solar cell will increase the conversion efficiency of GaAs solar cells. Therefore, it is confirmed that the triangular (or conical) shaped nano-grating structure is an excellent alternative AR coating for the high efficiency GaAs solar cells.
Acknowledgments This research is supported by the Centre for Smart Grid and Sustainable Power Systems, the undergraduate and postgraduate research students who worked with us in this research project, and the Faculty of Science and Engineering, Curtin University, Perth, Australia.