Measurement of internal optical reflection characteristics of solar cell back reflectors

The optimization work of high-efficient solar cells includes light-trapping schemes for the weakly absorbed near-infrared (NIR) photons. The light scattering properties of the back-reflector are here of particular interest. Novel back reflector designs that employ plasmonic and multi-stack interference effects require especially an experimental verification of the numerical simulations. Unfortunately, a good measurement of these scatter properties is nontrivial due to the refractive index of silicon and its resulting angle of total reflection. On planar wafers, light can therefore only be coupled in and out of silicon in a quite narrow angle, impossible to measure wider angles. Therefore we present an experimental setup to measure the angular resolved scatter properties of back-reflectors for IR photons.