Estimation of local built-in potential of amorphous silicon thin-film solar cells by Kelvin force microscopy

The local surface potential of pin-type hydrogenated amorphous silicon (a-Si:H) thin-film solar cells has been evaluated by Kelvin force microscopy (KFM). We have also estimated the local built-in potential of the solar cells by KFM. In the surface morphology image of the solar cells, large convex grains related to the textured structure of the substrate were found. The surface potential distribution related to the surface morphology was observed in the solar cells. A similar surface potential distribution was also found in an n-type hydrogenated microcrystalline Si (µc-Si:H) film. The surface potential of the solar cells was not the same as that of the n-type film. The difference in average surface potential between the n-type hydrogenated microcrystalline Si (µc-Si:H) film and the solar cells increased with increasing built-in potential. The difference in local surface potential on large convex grains was smaller than that in the region between the large convex grains.