Aluminum-boron solar cell contacts
View Patent ↗Formulations and methods of making solar cells are disclosed. In general, the invention provides a solar cell comprising a contact made from a mixture wherein, prior to firing, the mixture comprises at least one aluminum source, at least one boron source, and about 0.1 to about 10 wt % of a glass component. Within the mixture, the overall content of aluminum is about 50 wt % to about 85 wt % of the mixture, and the overall content of boron is about 0.05 to about 20 wt % of the mixture.
1. A solar cell comprising two separate layers, a silicon layer and a contact layer deposited over a surface of the silicon layer and made from a mixture,
wherein, prior to firing, the mixture comprises:
a. at least one aluminum source,
b. at least one boron source, and
c. about 0.1 to about 10 wt % of a glass component, wherein the glass component is devoid of intentionally added lead in any form, and wherein the glass component comprises:
(i) about 12 to about 50 mole % Bi 2 O 3 ,
(ii) about 25 to about 65 mole % SiO 2 ,
(iii) about 5 to about 15 mole % B 2 O 3 , and
(iv) about 4 to about 26 mole % K 2 O,
wherein the content of aluminum is about 50 wt% to about 85 wt % of the mixture, and
wherein the content of boron is about 0.05 to about 20 wt % of the mixture.
2. The solar cell of claim 1 wherein the aluminum source is selected from the group consisting of aluminum metal powder, an alloy of aluminum, an aluminum salt, organometallic aluminum, an oxide of aluminum, and an aluminum-containing glass.
3. The solar cell of claim 1 wherein the boron source is selected from the group consisting of boron metal powder, a alloy of boron, a salt of boron, boric acid, organometallic boron, an oxide of boron, and boron-containing glass.
4. The solar cell of claim 1 , wherein the aluminum source comprises an alloy of aluminum with a metal selected from the group consisting of boron, silicon, gallium, indium, antimony, tin, zinc, and magnesium.
5. The solar cell of claim 4 , wherein the aluminum alloy comprises about 60 to about 99.9 wt % aluminum and about 0.1 to about 40 wt % boron.
6. The solar cell of claim 1 , wherein the glass component further comprises ZnO, wherein the content of ZnO does not exceed about 55 mole %.
7. The solar cell of claim 1 , wherein the glass component further comprises a trivalent oxide of an element selected from the group consisting of an element having an atomic number of from 57 to 71, Al, Ga, In, Sc, and Y, and combinations thereof, provided that the combined total content of such trivalent oxides does not exceed about 25 mol %.
8. The solar cell of claim 7 , wherein the glass component further comprises an oxide of an element selected from the group Li, Na, Sb and combinations thereof, provided the combined total of such oxides together with K, does not exceed about 40 mol %.
9. The solar cell of claim 1 wherein the mixture further comprises an additive selected from the group consisting of SiO 2 , Sb 2 O 3 , In 2 O 3 , Ga 2 O 3 , SnO, ZnO, ZrO 2 , Al 2 O 3 , B 2 O 3 , Na 0.3 (Mg,Li) 3 Si 4 O 10 (OH) 2 , boric acid and combinations thereof.
10. A solar panel comprising the solar cell of claim 1 .
11. A process for making a solar cell contact, comprising applying an aluminum- and boron-containing paste to a silicon wafer, and firing the paste wherein, prior to firing, the mixture comprises
a. at least one aluminum source,
b. at least one boron source, and
c. about 0.1 to about 10 wt % of a glass component, wherein the glass component is devoid of intentionally added lead in any form, and wherein the glass component comprises:
(i) about 12 to about 50 mole % Bi 2 O 3 ,
(ii) about 25 to about 65 mole % SiO 2 ,
(iii) about 5 to about 15 mole % B 2 O 3 , and
(iv) about 4 to about 26 mole % K 2 O,
wherein the content of aluminum is about 50 wt % to about 85 wt % of the mixture,
wherein the content of boron is about 0.05 to about 20 wt % of the mixture.