Influence of front and back grating on light trapping in microcrystalline thin-film silicon solar cells

The optics of microcrystalline thin-film silicon solar cells with textured interfaces was investigated. The surface textures lead to scattering and diffraction of the incident light, which increases the effective thickness of the solar cell and results in a higher short circuit current. The aim of this study was to investigate the influence of the frontside and the backside texture on the short circuit current of microcrystalline thin-film silicon solar cells. The interaction of the front and back textures plays a major role in optimizing the overall short circuit current of the solar cell. In this study the front and back textures were approximated by line gratings to simplify the analysis of the wave propagation in the textured solar cell. The influence of the grating period and height on the quantum efficiency and the short circuit current was investigated and optimal grating dimensions were derived. The height of the front and back grating can be used to control the propagation of different diffraction orders in the solar cell. The short circuit current for shorter wavelengths (300-500 nm) is almost independent of the grating dimensions. For intermediate wavelengths (500 nm - 700 nm) the short circuit current is mainly determined by the front grating. For longer wavelength (700 nm to 1100 nm) the short circuit current is a function of the interaction of the front and back grating. An independent adjustment of the grating height of the front and the back grating allows for an increased short circuit current.