Silicon solar cell with nanocrystalline silicon down shifter: experiment and modelling

Materials used as luminescent down shifters (LDS) have to absorb light effectively in the spectral area where solar cells have poor internal quantum efficiency. At the same time these materials have to emit most of the absorbed spectral powers at lower energies where the internal quantum efficiency of the solar cell is close to the maximum. The effects of silicon nanocrystals prepared by thermal treatment of a silicon-rich-oxide (SRO) layer on the efficiency of c-Si cells are investigated in this paper. The SRO layer is characterized by a high photoluminescence peak at around 800 nm. Influence of the active layer on light transmission and on the modification of the optical spectra due to photoluminescence generation has been determined with the help of optical measurements and transfer matrix simulations. The solar cell efficiency for cells with and without down-shifting layer were measured under illumination with AM1.5G solar spectrum and compared with the simulations. Finally, we model the behavior of cells with and without LDS layer showing that a cell with LDS suffers less from bad surface passivation