Development of Rear Side Polishing Adapted to Advanced Solar Cell Concepts

Rear side passivated c-Si solar cells are gaining in the last years particular interest by research organisation and industrial solar cell manufacturers. Those devices typically rely on chemically polished rear surfaces before applying dielectric passivation layers. It is the purpose of this work to study the influence of the rear side polishing step on the performance of CZ-Si solar cells that have been textured with in-line alkaline texturing equipment for the formation of random pyramids on the front side of the wafer. Varying the chemical polishing step for the rear surface preparation, the surface roughness and its optical properties have been investigated with respect to the overall solar cell performance of screen printed solar cells with homogeneous emitter and rear side passivated surfaces with local Al BSF contacts. A wide process window was found for the rear side polishing process not requiring for perfectly polished rear surfaces when aiming for efficiencies above 19%. The influence of the resulting solar cell thickness has been looked at independently from the rear surface polishing process.