Metal versus dielectric back reflector for thin-film Si solar cells with impact of front electrode surface texture
Thin-film Si solar cells employ a back reflector (BR) for a more efficient use of the long wavelength light. Here, we have carried out a cross evaluation of metal (Ag-based) and dielectric (white paint-based) BR designs. Conclusive results have been reached regarding the most suitable BR type depending on the front electrode morphology, both with crater-like and pyramidal texture. The ZnO/Ag BR is found to be optically more efficient because of improved light trapping, although the gain tends to vanish for rougher front electrodes. Thanks to non-conventional Raman intensity measurements, this dependence on the front texture has been linked to the different weight of front and back interfaces in the light trapping process for the different morphologies. With rougher substrates, because the minor optical gain is accompanied by sputter-induced electronic deterioration of the solar cell during the ZnO buffer layer deposition, the white paint-based BR design is preferred. Copyright (c) 2016 John Wiley & Sons, Ltd.