Solderable polymer thick film conductive electrode composition for use in thin-film photovoltaic cells and other applications
View Patent ↗The invention is directed to a polymer thick film conductive composition comprising (a) a conductive silver-coated copper powder; and (b) an organic medium comprising two different resins and organic solvent, wherein the ratio of the weight of the conductive silver-coated copper powder to the total weight of the two different resins is between 5:1 and 45:1. The invention is further directed to a method of electrode grid and/or bus bar formation on thin-film photovoltaic cells using the composition and to cells formed from the method and the composition.
1. A method of forming a conductive grid on a thin-film photovoltaic cell, comprising the steps of:
(a) applying to the front-side of said thin-film photovoltaic cell a solderable polymer thick film conductive composition comprising:
(i) a conductive silver-coated copper powder; and
(ii) an organic medium comprising two different resins and organic solvent,
wherein the ratio of the weight of said conductive silver-coated copper powder to the total weight of said two different resins is between 5:1 and 45:1 and said two different resins are a phenoxy resin and a phenolic resin; and
(b) drying said composition.
2. The method of claim 1 , wherein said conductive silver-coated copper powder is silver-coated copper flakes.
3. The method of claim 2 , wherein said organic solvent comprises one or more components selected from the group consisting of: diethylene glycol ethyl ether acetate and butyl carbitol.
4. The method of claim 1 , wherein, based on the total weight of the composition, said silver-coated copper powder is 60 to 93 weight percent, the total weight of said two resins is 0.3 to 6 weight percent and said organic medium is 7 to 40 weight percent of said solderable polymer thick film conductive composition.
5. The method of claim 4 , the solderable polymer thick film conductive composition of claim 4 , wherein, based on the total weight of the composition, said silver-coated copper powder is 75 to 93 weight percent, the total weight of said two resins is 0.3 to 6 weight percent and said organic medium is 7 to 25 weight percent of said solderable polymer thick film conductive composition.
6. The method of claim 1 , wherein the front-side of said thin-film photovoltaic cell is sputtered with indium tin oxide.
7. A thin-film photovoltaic cell formed by the method of claim 1 .
8. A thin-film photovoltaic cell formed by the method of claim 2 .
9. A thin-film photovoltaic cell formed by the method of claim 3 .
10. A thin-film photovoltaic cell formed by the method of claim 4 .
11. A thin-film photovoltaic cell formed by the method of claim 5 .
12. A thin-film photovoltaic cell formed by the method of claim 6 .