Enhanced carrier collection at grain-boundary barriers in solar cells made from large grain polycrystalline material

The case of the solar cell in polycrystalline material is investigated specifically in view of the electronic properties of grain-boundaries. Material in thin film form, ribbons or cast ingots display a preponderance of vertically oriented grains. This and the fact that grain-boundaries are excellent photo-electric converters, when correctly contacted, is the basis for a new diffusion- and contacting scheme. It makes use of the grain-boundaries as vertical junctions, enhancing the photo-current. The argument is substantiated by a discussion of the electronic features of grain-boundaries under these conditions and the enhancement of the photovoltage due to the frequency extension of the photoresponse.