Method of production of CIS-based thin film solar cell
A method of production of a CIS-based thin film solar cell comprises the steps of forming an alkali control layer on a high strain point glass substrate, forming a back surface electrode layer on the alkali control layer, forming a CIS-based light absorption layer on the back surface electrode layer, and forming an n-type transparent conductive film on the CIS-based light absorption layer, wherein the alkali control layer is formed to a thickness which allows heat diffusion of the alkali metal which is contained in the high strain point glass substrate to the CIS-based light absorption layer and, furthermore, the CIS-based light absorption layer has an alkali metal added to it from the outside in addition to heat diffusion from the high strain point glass substrate.
1. A method of production of a CIS-based thin film solar cell, comprising the steps of,
forming an alkali control layer on a high strain point glass substrate,
forming a back surface electrode layer on said alkali control layer,
forming a CIS-based light absorption layer on said back surface electrode layer, and
forming an n-type transparent conductive film on said CIS-based light absorption layer,
wherein said alkali control layer is formed to a thickness which allows diffusion by heat treatment of the alkali metal which is contained in said high strain point glass substrate to said CIS-based light absorption layer and, furthermore, said CIS-based light absorption layer has an alkali metal added to it from the outside in addition to diffusion by heat treatment from said high strain point glass substrate.
2. A method of production of a CIS-based thin film solar cell as set forth in claim 1 , characterized in that said alkali control layer is formed of a silica film with a thickness of 3 to 12 nm.
3. A method of production of a CIS-based thin film solar cell as set forth in claim 2 , characterized in that said alkali control layer is formed of a silica film with a refractive index of 1.45 to 1.50 in range.
4. A method of production of a CIS-based thin film solar cell as set forth in claim 1 , characterized in that the amount of addition of said alkali metal is from 0.02 at % to 0.1 at %.
5. A method of production of a CIS-based thin film solar cell as set forth in claim 1 , characterized in that said alkali metal is Na.
6. A method of production of a CIS-based thin film solar cell as set forth in claim 5 , characterized in that said high strain point glass substrate has a thermal expansion coefficient of 8×10 −6 /° C. to 9×10 −6 /° C. in range and includes Na 2 O of 2 to 5 wt % in range.
7. A method of production of a CIS-based thin film solar cell as set forth in claim 1 , characterized in that said CIS-based light absorption layer is formed by forming a metal precursor film which contains said alkali metal on said back surface electrode layer and selenizing/sulfurizing the metal precursor film.
8. A method of production of a CIS-based thin film solar cell as set forth in claim 7 , characterized in that the metal precursor film is formed by sputtering and the alkali metal is added to the CuGa sputter target.
9. A method of production of a CIS-based thin film solar cell as set forth in claim 1 , characterized in that said CIS-based light absorption layer is made of a five component compound having Cu, In, Ga, Se, and S as main ingredients.
10. A method of production of a CIS-based thin film solar cell as set forth in claim 9 , characterized in that said CIS-based light absorption layer is formed by selenization/sulfurization of a multilayer structure which contains Cu, In, and Ga or a metal precursor film of mixed crystals of the same.