FIG. 18A is a plan view of a photovoltaic element as seen from its light-receivingsurface, and FIG. 18B is a sectional view of the photovoltaic element shown in FIG. 18A, which is taken along the line 18B--18B in FIG. 18A. In addition, FIG. 19A is a plan view of two photovoltaic elements connected in series as seen from theirlight-receiving surface, FIG. 19B is an enlarged view of the series-conne