Binary glass frits used in n-type solar cell production

Patent metadata

Field	Value
Publication number	US-10141459-B2
Application number	US-201314655301-A
Country	US
Kind code	B2
Filing date	Dec 23, 2013
Priority date	Dec 28, 2012
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

In general, the invention relates to electro-conductive pastes containing binary glass frits and photovoltaic solar cells, preferably n-type photovoltaic solar cells. More specifically, the invention relates to solar cell precursors, processes for preparation of solar cells, solar cells and solar modules.
The invention relates to a solar cell precursor comprising as precursor parts
i. a wafer with a back face and a front face, wherein the front face comprises a p-doped layer ii. a first paste comprising
Ag particles; Al particles in a range from about 0.01 to about 5 wt. %, based on the total weight of the paste; a vehicle; a glass frit in a range from about 0.1 to about 5 wt. %, based on the total weight of the paste, wherein the glass frit comprises a first glass frit with a glass transition temperature T gl and a further glass frit with a glass transition temperature T gf , wherein T gf differs from T gl by at least about 10° C.; an additive;
superimposed on a first area on said p-doped layer.

First claim

The invention claimed is:

1. A solar cell precursor comprising as precursor parts
i. a wafer with a back face and a front face, wherein the front face comprises a p-doped layer;
ii. a first paste comprising
Ag particles;
Al particles in a range from about 0.01 to about 5 wt. %, based on the total weight of the paste;
a vehicle;
a glass frit in a range from about 0.1 to about 5 wt. %, based on the total weight of the paste, wherein the glass frit comprises a first glass frit with a glass transition temperature T gl and a further glass frit with a glass transition temperature T gf , wherein both T gl and T gf are in a range from 320 to 500° C., and wherein T gf differs from T gl by at least 50° C.; and
an additive, wherein the first paste is superimposed on a first area on said p-doped layer.

2. The solar cell precursor according to claim 1 , wherein the first glass frit and the further glass frit are present in a weight ratio in a range from about 1:5 to about 5:1.

3. The solar cell precursor according to claim 1 , wherein the first paste satisfies at least one of the following criteria:
the viscosity of the first paste is in a range from about 5 to about 35 Pa·s;
the vehicle comprises one or more solvents, and all solvents present in the paste have a boiling point in a range from about 90 to about 300° C.

4. The solar cell precursor according to claim 1 , wherein the first paste satisfies at least one of the following criteria:
the Al particles have a d 50 , in a range from about 1 to about 5 μm;
the Ag particles have a d 50 in a range from about 1 to about 4 μm; and
the glass frit particles have a d 50 , in a range from about 0.1 to about 3 μm.

5. The solar cell precursor according to claim 1 , wherein the Ag particles are spherical.

6. The solar cell precursor according to claim 1 , wherein the solar cell precursor further comprises a further paste superimposed on a further area on the back face.

7. The solar cell precursor according to claim 6 , wherein the first area is smaller than the further area.

8. The solar cell precursor according to claim 6 , wherein the further paste comprises
Ag particles;
a vehicle
a glass frit; and
an additive.

9. The solar cell precursor according to claim 1 , wherein the thickness of the p-doped layer is in a range from about 10 nm to about 4 μm.

10. The solar cell precursor according to claim 1 , wherein the back face comprises an n-doped layer, wherein the n-doped layer has a greater thickness than the p-doped layer.

11. The solar cell precursor according to claim 1 , wherein the p-doped layer comprises B as a dopant.

12. The solar cell precursor according to claim 1 , wherein the back face comprises an n-doped layer comprising P as a dopant.

13. The solar cell precursor according to claim 1 , wherein one or more layers which act as anti-reflection layer and/or passivation layer are present between the p-doped layer and the superimposed first paste.

14. The solar cell precursor according to claim 13 , wherein at least one of the layers which function as anti-reflection layer and/or passivation layer comprises SiN x , wherein x stands for a positive but not necessarily whole number.

15. The solar cell precursor according to claim 1 , wherein the first paste is superimposed on the first area in a grid pattern.

16. The solar cell precursor according to claim 15 , wherein the grid pattern of the first paste superimposed on the first area comprises fingers with a width in a range from about 20 to about 100 μm and bus bars at an angle thereto in a range from about 70 to about 90° with a width in a range from about 0.5 to about 2.5 mm.

17. The solar cell precursor according to claim 1 , wherein the solar cell precursor comprises a further paste superimposed on a further area on the back face in a grid.

18. The solar cell precursor according to claim 17 , wherein the grid pattern of the further paste superimposed on the further area comprises fingers with a width in a range from about 20 to about 200 μm and bus bars at an angle thereto in a range from about 70 to about 90° with a width in a range from about 0.5 to about 2.5 mm.

19. The solar cell precursor according to claim 1 , wherein both T gl and T gf are in a range from 320° C. to 420° C.

20. The solar cell precursor according to claim 1 , wherein the d 50 of the Ag particles is in the range from about 1 μm to about 4 μm.

21. The solar cell precursor according to claim 1 , wherein both T gl and T gf are in a range from 320° C. to 450° C.

22. A process for producing a solar cell comprising the steps
providing a solar cell precursor comprising as precursor parts;
i. a wafer with a back face and a front face, wherein the front face comprises a p-doped layer;
ii. a first paste comprising
Ag particles;
Al particles in a range from about 0.01 to about 5 wt. %, based on the total weight of the paste;
a vehicle;
a glass frit in a range from about 0.1 to about 5 wt. %, based on the total weight of the paste, wherein the glass frit comprises a first glass frit with a glass transition temperature T gl and a further glass frit with a glass transition temperature T gf , wherein both T gl and T gf are in a range from 320 to 500° C., and wherein T gf differs from T gl by at least 50° C.; and
an additive, wherein the first paste is superimposed on a first area on said p-doped layer; and

firing the solar cell precursor in order to obtain the solar cell.

23. The process for producing a solar cell according to claim 22 , wherein firing of said solar cell precursor satisfies at least one of the following criteria:
holding temperature in a range from about 700 to about 900° C.;
time at the holding temperature in a range from about 1 to about 10 s.

24. The process according to claim 22 , wherein the first paste is applied to the front face through a screen.

25. The process according to claim 24 , wherein the application through a screen satisfies at least one of the following parameters:
mesh count in a range from about 290 to about 400/inch;
wire thickness in a range from about 10 to about 30 μm;
emulsion over mesh (EoM) thickness in a range from about 5 to about 25 μm;
finger spacing in a range from about 1 to about 3 mm.

26. A solar cell obtainable from a process according to claim 22 .

27. A module comprising at least one solar cell according to claim 26 and at least another solar cell.

28. A solar cell precursor comprising as precursor parts
i. a wafer with a back face and a front face, wherein the front face comprises a p-doped layer;
ii. a first paste comprising
Ag particles;
Al particles in a range from about 0.01 to about 5 wt. %, based on the total weight of the paste;
a vehicle;
a glass frit in a range from about 0.1 to about 5 wt. %, based on the total weight of the paste, wherein the glass frit comprises a first glass frit with a glass transition temperature T gl and a further glass frit with a glass transition temperature T gf , wherein both T gl and T gf are in a range from 320 to 450° C., and wherein T gf differs from T gl by at least 10° C.; and
an additive, wherein the first paste is superimposed on a first area on said p-doped layer.

29. A solar cell precursor comprising as precursor parts
i. a wafer with a back face and a front face, wherein the front face comprises a p-

Assignees

• Heraeus Deutschland Gmbh & Co Kg

Inventors

• König Markus
• Hörteis Matthias
• Zhang Weiming

Classifications

• C03C8/18

  containing free metals · CPC title

• Y02E10/50

  Photovoltaic [PV] energy · CPC title

• C03C8/22

  containing two or more distinct frits having different compositions · CPC title

• H01L31/022425 Primary

  Electricity · mapped topic

• H01L31/18

  Electricity · mapped topic