Light Trapping in Thin-Film Silicon Solar Cells with periodic Nano-Structures

This article is presented with the courtesy and permission of Hasse, C. and Stiebig, H. , Forschungszentrum Juelich who gave a presentation of their work at the CST European User group Meeting at Boppard, Germany, 9-10th March 2006.

The current developments in solar cell technology show a clear tendency from the wafer based silicon cell technology to a low cost thin-film solar cell approach. Efficient thin-film silicon solar cells based on microcrystalline silicon (μc-Si:H) with an absorber layer in the micrometer range require effective light trapping and enhanced light incoupling for the entire sun spectrum. The established approach to increase the light path within thin-film silicon solar cells is the application of randomly textured transparent conductive oxides. Previous investigations of light trapping in thin-film devices have been conducted with often misleading far field measurements. As an alternative to randomly textured substrates light incoupling and light trapping in diodes with periodically textured substrates were investigated by an experimental and numerical study.

Optical simulations based on the Finite Integration Technique (FIT) are a sophisticated approach to analyze the light propagation in thin-film devices and study the optical properties of nano-textured interfaces in 3-dimensions. The geometry of the device with a typical power  loss plot is shown in Figure 1. The good agreement between the experimental data and solar cell simulations shows the reliability and versatility of the performed FIT simulations to investigate nano-optics of thin-film solar cell devices in 3 dimensions. More information is available on request.