Light trapping effects in thin film silicon solar cells
We present advanced light trapping concepts for thin film silicon solar cells. When an amorphous and a microcrystalline absorber layers are combined into a micromorph tandem cell, light trapping becomes a challenge because it should combine the spectral region from 600 to 750 nm for the amorphous top cell and from 800 to 1100 for the microcrystalline bottom cell. Because light trapping is typically achieved by growing on textured substrates, the effect of interface textures on the material and electric properties has to be taken into account, and importantly, how the surface textures evolve with the thickness of the overgrowing layers. We present different scenarios for the n-i-p configuration on flexible polymer substrates and p-i-n cells on glass substrate, and we present our latest stabilized efficiencies of 9.8% and 11.1%, respectively.