Multilayer transparent electroconductive film and method for manufacturing same, as well as thin-film solar cell and method for manufacturing same

A method for manufacturing a multilayer transparent electroconductive film having a transparent electroconductive film (I) mainly composed of zinc oxide;

• and a transparent electroconductive film (II) mainly composed of zinc oxide, having a composition different from the composition of the transparent electroconductive film (I), which is stacked on the transparent electroconductive film (I), comprising the steps of:
• by using an oxide sintered body target that is mainly composed of zinc oxide and contains one or more added elements selected from aluminum and gallium, with the content of the added elements being in a range represented by the following inequality (3), forming the transparent electroconductive film (I) by using a sputtering method under conditions of a sputtering gas pressure in a range from 0.1 to 0.8 Pa and a substrate temperature in a range from room temperature to 400° C., and
• by using an oxide sintered body target that is mainly composed of zinc oxide and contains one or more added elements selected from aluminum and gallium, with the content of the added elements being in a range represented by the following inequality (4), forming the transparent electroconductive film (II) by using a sputtering method under conditions of a sputtering gas pressure in a range from 2.0 to 15.0 Pa and a substrate temperature in a range from 300 to 600° C.:
• −2.18×[Al]+1.74≦[Ga]≦−1.92×[Al]+6.10 (3)
• —[Al]+0.30≦[Ga]≦−2.68×[Al]+1.74 (4)
• (where [Al] is the aluminum content expressed as the atomic ratio (%) Al/(Zn+Al), and [Ga] is the gallium content expressed as the atomic ratio (%) Ga/(Zn+Ga)).

A thin-film solar cell comprising:

• a multilayer transparent electroconductive film, a photoelectric conversion layer unit and a back electrode layer that are successively stacked on a translucent substrate,
• wherein the multilayer transparent electroconductive film comprises:
• a transparent electroconductive film (I) mainly composed of zinc oxide;
• and a transparent electroconductive film (II) mainly composed of zinc oxide, having a composition different from the composition of the transparent electroconductive film (I), which is stacked on the transparent electroconductive film (I), and
• wherein the transparent electroconductive film (I) contains one or more added elements selected from aluminum and gallium, with the content of the added elements being in a range represented by the following inequality (5), and the transparent electroconductive film (II) contains one or more added elements selected from aluminum and gallium, with the content of the added elements being in a range represented by the following inequality (6):
• −2.18×[Al]+1.74≦[Ga]≦−1.92×[Al]+6.10 (5)
• —[Al]+0.30≦[Ga]≦−2.68×[Al]+1.74 (6)
• (where [Al] is the aluminum content expressed as the atomic ratio (%) Al/(Zn+Al), and [Ga] is the gallium content expressed as the atomic ratio (%) Ga/(Zn+Ga)).

A method for manufacturing a thin-film solar cell comprising:

• a multilayer transparent electroconductive film, a photoelectric conversion layer unit and a back electrode layer that are successively stacked on a translucent substrate, wherein the multilayer transparent electroconductive film comprises:
• a transparent electroconductive film (I) mainly composed of zinc oxide;
• and a transparent electroconductive film (II) mainly composed of zinc oxide, having a composition different from the composition of the transparent electroconductive film (I), which is stacked on the transparent electroconductive film (I), comprising the steps of:
• by using an oxide sintered body target that is mainly composed of zinc oxide and contains one or more added elements selected from aluminum and gallium, with the content of the added elements being in a range represented by the following inequality (7), forming the transparent electroconductive film (I) by using a sputtering method under conditions of a sputtering gas pressure in a range from 0.1 to 0.8 Pa and a substrate temperature in a range from room temperature to 400° C., and
• by using an oxide sintered body target that is mainly composed of zinc oxide and contains one or more added elements selected from aluminum and gallium, with the content of the added elements being in a range represented by the following inequality (8), forming the transparent electroconductive film (II) by using a sputtering method under conditions of a sputtering gas pressure in a range from 2.0 to 15.0 Pa and a substrate temperature in a range from 300 to 600° C.:
• −2.18×[Al]+1.74≦[Ga]≦−1.92×[Al]+6.10 (7)
• —[Al]+0.30≦[Ga]≦−2.68×[Al]+1.74 (8)
• (where [Al] is the aluminum content expressed as the atomic ratio (%) Al/(Zn+Al), and [Ga] is the gallium content expressed as the atomic ratio (%) Ga/(Zn+Ga)).