Metal substrate for dye-sensitized solar cell

1. A metal substrate made of only metal for a dye-sensitized solar cell, comprising a three-layer clad material consisting of:

a nonporous first metal layer, arranged on an anode side of a dye-sensitized solar cell element, made of a metal having corrosion resistance against an electrolyte of said dye-sensitized solar cell element, a thickness of said nonporous first metal layer is at least 20 μm,

a second metal layer made of a metal having lower electrical resistance than said nonporous first metal layer and bonded to a side of said nonporous first metal layer opposite to said dye-sensitized solar cell element, and

a third metal layer bonded to a side opposite to said nonporous first metal layer being in direct contact with said second metal layer, wherein

said nonporous first metal layer is made of Ti,

said second metal layer is made of Cu,

said third metal layer is made of ferritic stainless steel containing at least about 16% and not more than about 18% of Cr,

wherein the metal substrate further comprises a catalyst layer formed on a substrate surface of said nonporous first metal layer closer to said dye-sensitized solar cell element,

the thickness of said nonporous first metal layer and a thickness of said third metal layer are substantially identical to each other, and

a ratio of a surface area to a plane area on said substrate surface of said nonporous first metal layer closer to said dye-sensitized solar cell element is at least 1.05.

2. The metal substrate made of only metal for a dye-sensitized solar cell according to claim 1 , wherein said nonporous first metal layer and said second metal layer constitute an anode of said dye-sensitized solar cell element.

3. The metal substrate made of only metal for a dye-sensitized solar cell according to claim 1 , wherein

a thickness of said second metal layer is at least 20% of a total thickness at least including the thickness of said nonporous first metal layer and the thickness of said second metal layer.

4. The metal substrate made of only metal for a dye-sensitized solar cell according to claim 3 , wherein the thickness of said second metal layer is at least 50% of said total thickness at least including the thickness of said nonporous first metal layer and the thickness of said second metal layer.

5. The metal substrate made of only metal for a dye-sensitized solar cell according to claim 1 , wherein

the thickness of said nonporous first metal layer is at least 15% of a total thickness at least including the thickness of said nonporous first metal layer, and a thickness of said second metal layer.

6. The metal substrate made of only metal for a dye-sensitized solar cell according to claim 1 , wherein said third metal layer is made of a metal having higher corrosion resistance than said metal constituting said second metal layer.

7. The metal substrate made of only metal for a dye-sensitized solar cell according to claim 1 , wherein

a thickness of said second metal layer is at least 20% and not more than 70% of a total thickness at least including the thickness of said nonporous first metal layer, the thickness of said second metal layer and a thickness of said third metal layer.

8. The metal substrate made of only metal for a dye-sensitized solar cell according to claim 7 , wherein the thickness of said second metal layer is at least 30% and not more than 60% of said total thickness at least including the thickness of said nonporous first metal layer, the thickness of said second metal layer and the thickness of said third metal layer.

9. The metal substrate made of only metal for a dye-sensitized solar cell according to claim 1 , wherein the electrical resistance of said second metal layer is not more than 1/20 of the electrical resistance of said nonporous first metal layer.

10. The metal substrate made of only metal for a dye-sensitized solar cell according to claim 1 , wherein arithmetic mean roughness Ra is at least 0.10 μm and ten point height of irregularities Rzjis is at least 0.50 μm on said substrate surface of said nonporous first metal layer closer to said dye-sensitized solar cell element.

11. The metal substrate made of only metal for a dye-sensitized solar cell according to claim 10 , wherein said arithmetic mean roughness Ra is at least 0.22 μm and said ten point height of irregularities Rzjis is at least 1.20 μm on said substrate surface of said nonporous first metal layer closer to said dye-sensitized solar cell element.

12. The metal substrate made of only metal for a dye-sensitized solar cell according to claim 1 , wherein the difference between the thermal expansion coefficient of said third metal layer and the thermal expansion coefficient of said nonporous first metal layer is smaller than the difference between the thermal expansion coefficient of said second metal layer and the thermal expansion coefficient of said nonporous first metal layer.