NOVELTY - A thin film polycrystalline solar cell comprises a substrate (1) and three semiconductor layers (3, 4, 5). Crystal grains grown from crystal nuclei generated in the first layer are continuously grown to form the first and second semiconductor layers, and are also horizontally grown to contact neighboring crystal grains, and are also perpendicularly grown to form an interface with the third semiconductor layer.    USE - As a thin film polycrystalline solar cell.    ADVANTAGE - The thin film polycrystalline solar cell has good characteristics regarding the short-circuit current and the fill factor. The charge generated in the crystal grains is transported in the direction perpendicular to the substrate without being affected by grain boundaries and a high-resistance layer of non-doped amorphous silicon, successfully enhancing the fill factor characteristics. The average grain diameter of the crystal grains is not less than 100 nm and the shape of the crystals at the interface is provided with an unevenness of not less than 20 nm, giving a large short-circuit current characteristic.    DETAILED DESCRIPTION - A thin film polycrystalline solar cell comprises:    (i) a substrate (1);    (ii) a first semiconductor layer (3) on the substrate, comprising silicon highly doped with a conductivity type controlling impurity;    (iii) a second semiconductor layer (4) on the first layer, comprising polycrystalline silicon slightly doped with a conductivity-type controlling impurity of the same conductivity type as that of the first layer; and    (iv) a third semiconductor layer (5) on the second layer, highly doped with a conductivity-type controlling impurity of a conductivity type opposite to that of the impurities for the doping of the first and second layers.    Crystal grains grown from crystal nuclei generated in the first layer are continuously grown to form the first and second semiconductor layers, and are also horizontally grown to contact neighboring crystal grains, and are also perpendicularly grown to form an interface with the third semiconductor layer.    INDEPENDENT CLAIMS are also included for the following:    (I) a further thin film polycrystalline solar cell; and    (II) two processes for the production of a thin film polycrystalline solar cell.    DESCRIPTION OF DRAWING(S) - The figure shows a solar cell.    Substrate (1)    Electroconductive metal film (2)    First silicon thin film semiconductor layer (3)    Second silicon thin film semiconductor layer (4)    Third silicon thin film semiconductor layer (5)    Collecting electrodes (6)    Anti-reflection layer (7)