Simulation of optical waves in thin-film solar cells

In order to increase the efficiency of thin-film solar cells, the nanostructure of these cells has to be optimized. To this end, simulations of the optical wave in thin-film solar cells are required. The frequency dependence of the refraction index of materials, like amorphous silicon (a-Si:H), cannot be described by dispersive models like Drude model. Therefore, single frequency simulations for the whole solar spectrum have to be performed. To discretize materials with negative permittivity efficiently, we developed a new finite-difference-frequency-domain method to avoid computationally intensive simulations. To demonstrate the efficiency of our method, we present 3-dimensional simulations for a tandem solar cell including interfaces described by AFM-scans. Plasmonic effects at the silver back-contact show the efficiency of our discretization in case of materials with negative permittivity.