DYE-SENSITIZED SOLAR CELL AND METHOD FOR MANUFACTURING THE SAME
A dye-sensitized solar cell comprises a photoelectrode formed by using a stainless steel plate and a counter electrode formed by using a light-transmissive electroconductive material, wherein the photoelectrode comprises, as the substrate thereof, a stainless steel plate having a chemical composition containing Cr: at least 16% by mass and Mo: at least 0.3% by mass and having a roughened surface in which pit-like indentations are formed and which is controlled to have an arithmetic average roughness Ra of at least 0.2 μm, and comprises, as formed on the roughened surface of the substrate, a sensitizing dye-carrying semiconductor layer, the counter electrode has a catalyst thin-film layer formed on the surface of the light-transmissive electroconductive material and has visible light tansmissiveness, and the semiconductor layer of the photoelectrode and the catalyst thin-film layer of the counter electrode face each other via an electrolytic solution.
1 . A dye-sensitized solar cell comprising a photoelectrode formed by using a stainless steel plate and a counter electrode formed by using a light-transmissive electroconductive material, wherein:
the photoelectrode comprises, as the substrate thereof, a stainless steel plate having a chemical composition corresponding to a ferritic stainless steel containing Cr: at least 16% by mass and Mo: at least 0.3% by mass and defined by JIS G4305:2005, and having a roughened surface in which pit-like indentations are formed and which is controlled to have an arithmetic average roughness Ra of at least 0.2 μm, and comprises, as formed on the roughened surface of the substrate, a sensitizing dye-carrying semiconductor layer;
the counter electrode has a catalyst thin-film layer formed on the surface of the light-transmissive electroconductive material and has visible light transmissiveness; and
the semiconductor layer of the photoelectrode and the catalyst thin-film layer of the counter electrode face each other via an electrolytic solution.
2 . The dye-sensitized solar cell as claimed in claim 1 , wherein the stainless steel for use in the photoelectrode has a chemical composition corresponding to an austenitic stainless steel containing Cr: at least 16% by mass and Mo: at least 0.3% by mass and defined by JIS G4305:2005.
3 . The dye-sensitized solar cell as claimed in claim 1 , wherein the stainless steel for use in the photoelectrode is a ferritic stainless steel comprising, by mass, C: at most 0.15%, Si: at most 1.2%, Mn: at most 1.2%, P: at most 0.04%, S: at most 0.03%, Ni: at most 0.6%, Cr: from 16 to 32%, Mo: from 0.3 to 3%, Cu: from 0 to 1%, Nb: from 0 to 1%, Ti: from 0 to 1%, Al: from 0 to 0.2%, N: at most 0.025%, B: from 0 to 0.01%, with a balance of Fe and inevitable impurities.
4 . The dye-sensitized solar cell as claimed in claim 1 , wherein the stainless steel for use in the photoelectrode is an austenitic stainless steel comprising, by mass, C: at most 0.15%, Si: at most 4%, Mn: at most 2.5%, P: at most 0.045%, S: at most 0.03%, Ni: from 6 to 28%, Cr: from 16 to 32%, Mo: from 0.3 to 7%, Cu: from 0 to 3.5%, Nb: from 0 to 1%, Ti: from 0 to 1%, Al: from 0 to 0.1%, N: at most 0.3%, B: from 0 to 0.01%, with a balance of Fe and inevitable impurities.
5 . The dye-sensitized solar cell as claimed in claim 1 , wherein the counter electrode has visible light transmissiveness of such that the light transmittance at a wavelength of 500 nm is at least 55%.
6 . The dye-sensitized solar cell as claimed in claim 1 , wherein the catalyst to constitute the catalyst thin-film layer of the counter electrode is platinum, nickel or an electroconductive polymer.
7 . The dye-sensitized solar cell as claimed in claim 6 , wherein the catalyst is platinum or nickel, and the thickness of the catalyst thin-film layer is from 0.5 to 5 nm.
8 . The dye-sensitized solar cell as claimed in claim 6 , wherein the catalyst is an electroconductive polymer, and the thickness of the catalyst thin-film layer is from 1 to 10 nm.
9 . The dye-sensitized solar cell as claimed in claim 1 , wherein the roughened surface of the substrate stainless steel plate for use in the photoelectrode is such that the part thereof at which the neighboring indentations join together has an edged boundary.
10 . A method for producing a dye-sensitized solar cell of claim 1 , which comprises:
a step of etching a stainless steel plate in an aqueous solution with a ferric ion existing therein to form pit-like indentations in the plate, thereby giving a substrate that has a roughened surface with an arithmetic average roughness Ra of at least 0.2 μm,
a step of forming, on the roughened surface, a coating film that contains oxide semiconductor particles,
a step of firing the coating film to form a porous semiconductor layer,
a step of dipping the semiconductor layer in a solvent with a sensitizing dye dispersed therein to make the semiconductor layer carry the sensitizing dye, thereby giving a photoelectrode that comprises the sensitizing dye-carrying semiconductor layer on the roughened surface of the substrate stainless steel plate, and
a step of arranging the photoelectrode and the visible light-transmissive counter electrode with the catalyst thin-film layer formed on the surface of the light-transmissive electroconductive material, in such a manner that the semiconductor layer of the photoelectrode could face the catalyst thin-film layer of the counter electrode, and introducing an electrolytic solution into the space between the two electrodes.
11 . The method for producing a dye-sensitized solar cell as claimed in claim 10 , wherein the aqueous solution with a ferric ion existing therein is an aqueous, ferric chloride-containing solution.