The thin film solar cell which used CuInSe2 (CIS based thin film) which is a semiconductor thin film of chalcopyrite structure composed of a group Ib element, a group IIIb element, and a group VIb element, or Cu(In, Ga)Se2 (CIGS based thin film) which dissolved Ga to the CuInSe2 for an optical absorption layer shows high energy conversion efficiency, and has advantage that there is little degradation of the efficiency by light irradiation etc.
However, film formation by 550 degrees C. from a viewpoint of degradation of film quality and increase of leakage current is general, in formation of the CIS based thin film which is the semiconductor thin film of chalcopyrite structure, or the CIGS based thin film which dissolves Ga to CIS based thin film. When it forms at low temperature rather than 550 degrees C., it has been considered that particle diameter is small composed and dark current characteristics degrade, conventionally. In addition, the heat-resistant limitation of an integrated circuit is about 400 degrees C.
It is already disclosed about a photoelectric conversion device which used a compound semiconductor thin film of chalcopyrite structure to reduce dark current substantially, and a fabrication method for the such photoelectric conversion device (for example, refer to Patent Literature 1 and Patent Literature 2).
Also, it is already disclosed about a formation method by a selenium process of a high quality CIGS based thin film (for example, refer to Patent Literature 3 and Patent Literature 4).
On the other hand, it is already disclosed about: a solid state imaging element characterized by forming a switching device by a thin film transistor on a substrate and composing to laminate a sensor area by an amorphous semiconductor layer via the picture element electrode connected to the above-mentioned switching device; or a solid state imaging element composed to form by an insulating substrate as the above-mentioned substrate (for example, refer to Patent Literature 5).
In the solid state imaging element disclosed in Patent Literature 4, since the amorphous semiconductor layer is applied into the photosensing area, a photoelectric conversion wavelength is mainly a visible light wavelength region.
In such a conventional solid state imaging element, since a low electric field is applied to a photoelectric conversion film and an electric charge is detected, the photoelectric conversion film itself has no multiplication function.
Citation List
Patent Literature 1: Japanese Patent Application Laying-Open Publication No. 2007-123720
Patent Literature 2: Japanese Patent Application Laying-Open Publication No. 2007-123721
Patent Literature 3: U.S. Pat. No. 5,436,204
Patent Literature 4: U.S. Pat. No. 5,441,897
Patent Literature 5: Japanese Patent Application Laying-Open Publication No. 2001-144279