Fundamental optical simulations of light trapping in microcrystalline silicon thin-film solar cells

Abstract

Thin-film silicon solar cells require an effective light trapping and a low reflectivity over the entire sun spectrum. As the optics in thin-film devices is not understood in detail optical simulations can be a useful tool to investigate the wave propagation in textured layer stacks. For microcrystalline (µc-Si:H) and amorphous (a-Si:H) silicon solar cells transparent conductive oxides (ZnO) with randomly rough textured interfaces are commonly used to achieve an improved light in-coupling into the cell and light scattering at the rough interfaces. Since periodically textured substrates offer the possibility to design the solar cell in accordance to a waveguide, the solar cells with integrated grating coupler and Bragg reflector gain more and more in importance. To get more insight into light propagation a detailed computational study focusing on the relation of the incoming light wave and the structure size and structure shape of the interface texture is extremely valuable.