NOVELTY - The element (40) has a substrate (10) provided with electrical insulation layer (16) formed on surface (14a) of metallic substrate. A diffusion prevention layer (52) is formed on electrical insulation layer. An alkali supply layer (50) is electrically conductive and formed on prevention layer. A photoelectric conversion layer (34) comprising compound semiconductor layer and formed on lower electrode. The electrodes are formed on conversion layer and alkali layer. The prevention layer prevents diffusion of alkali metal from alkali layer to substrate within insulation layer.    USE - Photoelectric conversion element used in thin-film solar cell (claimed) used as power source for building e.g. residence housing.    ADVANTAGE - The photoelectric conversion element having high insulation properties is enabled to sufficiently maintaining and controlling the precision and reproducibility of amount of alkali metal supplied to photoelectric conversion layer, so as to increase the photoelectric conversion efficiency. The productivity of the photoelectric conversion element can be improved. The diffusion prevention layer can be enabled to form electrical insulation layer of substrate, and to form conductive alkali supply layer, so that the diffused amount of alkali metal element ions or alkali earth metal element ions provided into the photoelectric conversion layer can be increased and supplied quantity of conversion element can be controlled with good reproducibility. Thus the high photoelectric conversion efficiency of photoelectric conversion element can be achieved. The thermal expansion coefficients of diffusion prevention layer, metallic substrate, and photoelectric conversion layer can be enabled to make uniform, so that the adhesion between diffusion prevention layer, metallic substrate and photoelectric conversion layer can be maintained and improved. Thus the delamination of metallic substrate and photoelectric conversion layer can be prevented. The alkali metal content of the alkali supply layer can be enabled to increase sufficiently, the alkali metal can be supplied to photoelectric conversion layer so as to improve the conversion efficiency. The thin-film solar cell sub-module and solar cell module can be achieved, so that the durability and storage life of the thin-film solar cell can be extended and improved. The copper-indium-gallium-selenide CIGS crystal quality of photoelectric conversion layer can be improved and hence the conversion efficiency of conversion layer can be enhanced. The weight of the photo electric conversion element is reduced while improving flexibility.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for the method of manufacturing a photoelectric conversion element.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the photoelectric conversion element.    Substrate (10)    Surface (14a)    Electrical insulation layer (16)    Photoelectric conversion layer (34)    Photoelectric conversion element (40)    Alkali supply layer (50)    Diffusion prevention layer (52)