Thick-film pastes containing lead- and tellurium-oxides, and their use in the manufacture of semiconductor devices
The present invention provides a thick-film paste for printing the front-side of a solar cell device having one or more insulating layers. The thick-film paste comprises an electrically conductive metal, and a lead-tellurium-oxide dispersed in an organic medium.
1. A thick-film paste composition for use in forming an electrical connection in a photovoltaic device comprising a semiconductor substrate having at least one insulating layer on a main surface thereof, the composition comprising:
a) 95.5 to 99.5% by weight of an electrically conductive metal or derivative thereof, based on total solids in the composition;
b) 0.5 to 4.5% by weight based on solids of a lead-tellurium-oxide, wherein the mole ratio of lead to tellurium in the lead-tellurium-oxide is between 5/95 and 95/5, the lead-tellurium oxide comprises at most 67.72% of PbO by weight of the lead-tellurium-oxide and comprises at least 32.28% of TeO 2 by weight of the lead-tellurium-oxide, and the lead-tellurium-oxide comprises one or more of P 2 O 5 , Al 2 O 3 , TiO 2 , Cr 2 O 3 , Mn 2 O 3 , Fe 2 O 3 , CoO, Co 2 O 3 , NiO, CuO, Ga 2 O 3 , GeO 2 , Rb 2 O, Cs 2 O, SrO, BaO, In 2 O 3 , SnO 2 , Sb 2 O 3 , and CeO 2 in an amount ranging from greater than 0 to less than 9% by weight of the lead-tellurium oxide, and the lead-tellurium oxide is at least partially crystalline; and
c) an organic medium;
and wherein the thick-film paste, when fired, is capable of penetrating the at least one insulating layer.
2. The thick-film paste composition of claim 1 , wherein the lead-tellurium-oxide comprises at least one oxide of one or more elements selected from the group consisting of Si, Zn, As, Se, Mo, Ag, Nb, Cd, Y, La, Nd, Pr, Gd, Sm, Dy, Eu, Ho, Yb, Lu, Hf, Ta, W, and Bi.
3. The thick-film paste composition of claim 1 , comprising the lead-tellurium-oxide in an amount ranging from 0.5 to 3.45% by weight based on solids.
4. The thick-film paste composition of claim 1 , wherein the lead-tellurium-oxide comprises at most 63.09% of PbO by weight of the lead-tellurium oxide.
5. The thick-film paste composition of claim 1 , wherein the lead-tellurium-oxide comprises at least 36.91% of TeO 2 by weight of the lead-tellurium oxide.
6. The thick-film paste composition of claim 5 , wherein the lead-tellurium-oxide comprises at most 63.09% of PbO by weight of the lead-tellurium oxide.
7. The thick-film paste composition of claim 1 , wherein the lead-tellurium-oxide is Cd-free.
8. The thick-film paste composition of claim 1 , wherein the lead-tellurium-oxide is As-free.
9. The thick-film composition of claim 1 , wherein the lead-tellurium-oxide further comprises Li 2 O in an amount ranging from greater than 0 to 5% by weight of the lead-tellurium oxide.
10. The thick-film composition of claim 1 , wherein the lead-tellurium-oxide further comprises Ag 2 O in an amount ranging from greater than 0 to 29.61% by weight of the lead-tellurium oxide.
11. The thick-film composition of claim 1 , wherein the lead-tellurium-oxide comprises one or more glass frits.
12. The thick-film composition of claim 1 , wherein the electrically conductive metal comprises silver.