Solar cell comprising a p-doped silicon wafer and an aluminum electrode

1. A solar cell comprising:

a p-doped silicon wafer, wherein the p-doped silicon wafer comprises a light-receiving side and a back side; and

an aluminum electrode formed on the back side of the silicon wafer;

wherein the aluminum electrode comprises an aluminum base layer formed adjacently on the back side of the silicon wafer and an aluminum cover layer formed on the aluminum base layer, and

wherein the aluminum cover layer comprises aluminum and boron oxide (B 2 O 3 ).

2. A solar cell of claim 1 , wherein the weight ratio (aluminum/B 2 O 3 ) in the aluminum cover layer is 100/192-100/3.2

3. A solar cell of claim 2 , wherein the weight ratio (aluminum/B 2 O 3 ) in the aluminum cover layer is 100/80-100/3.2.

4. A solar cell of claim 1 , wherein thickness of the aluminum electrode is equal to or more than 10.0 μm.

5. A solar cell of claim 1 , wherein a passivation layer is formed on the silicon layer between the p-doped silicon wafer and the aluminum electrode.

6. A solar cell of claim 1 , wherein the aluminum base layer is substantially free of boron oxide.

7. A method for manufacturing a solar cell, comprising the steps of:

preparing a p-doped silicon wafer, wherein the p-doped silicon wafer comprises a light-receiving side and a back side;

applying a first aluminum paste comprising aluminum on the back side of the p-doped wafer;

applying a second aluminum paste comprising aluminum and boron compound; and

firing the first aluminum paste and the second aluminum paste to form an aluminum electrode comprising an aluminum base layer and an aluminum cover layer that derives from the first aluminum paste and the second aluminum paste respectively,

wherein the boron compound is oxidized to boron oxide (B 2 O 3 ) during the firing.

8. A method of claim 7 , wherein the boron compound is selected from the group consisting of boron, boric acid (B(OH) 3 ), boron trioxide (B 2 O 3 ), borax (Na 2 B 4 O 5 ), borate ester, boronic acid, and organic boron compound.

9. A method of claim 7 , the first aluminum paste and the second aluminum paste are fired at the same time.

10. A method of claim 7 , the first aluminum paste is fired prior to the firing of the second aluminum paste.

11. A method of claim 7 , the first aluminum paste and the second aluminum paste are fired at 600-900° C.

12. A method of claim 7 , wherein the weight ratio (aluminum/B 2 O 3 ) in the aluminum cover layer is 100/192-10013.2

13. A method of claim 12 , wherein the weight ratio (aluminum/B 2 O 3 ) in the aluminum cover layer is 100/80-100/3.2.

14. A method of claim 7 , wherein thickness of the aluminum electrode is equal to or more than 10.0 μm.

15. A method of claim 7 , further comprising a step of forming a passivation layer on the silicon layer between the p-doped silicon wafer and the aluminum electrode.

16. A method of claim 7 , wherein the first aluminum paste is substantially free of boron.