Printability and profile control of screen-printed gridlines by rheological manipulation
A conductive composition is disclosed. The conductive composition includes a plurality of silver particles and one or more cellulose-based binders. The composition also includes an amount of glass frit, an organic solvent and a plurality of carbon nanotubes, where the conductive composition is formed into a cross-sectional triangular shape, which may include a top cross-sectional dimension and a bottom cross-sectional dimension, where a ratio of the top cross-sectional dimension to the bottom cross-sectional dimension is 0.8 or less. A screen-printed gridline and a method of printing gridlines is also disclosed where the gridlines may be incorporated into a solar cell device.
1 . A conductive composition, comprising:
a plurality of silver particles;
one or more cellulose-based binders;
an amount of glass frit;
an organic solvent; and
a plurality of carbon nanotubes; and wherein:
a viscosity of the conductive composition is from about 300,000 cP to about 50,000 cP at a shear rate of from about 10/sec to about 40/sec.
2 . The conductive composition of claim 1 , wherein the cross-sectional triangular shape comprises a cross-sectional height of from about 15 μm to about 40 μm.
3 . The conductive composition of claim 1 , wherein the silver particles are present in an amount of from about 10% to about 99% by a total weight of the conductive composition.
4 . The conductive composition of claim 1 , wherein the amount of glass frit has a particle size of 5 μm or less.
5 . The conductive composition of claim 1 , wherein the carbon nanotubes are present in an amount of from about 0.01% to about 20% by a total weight of the conductive composition.
6 . The conductive composition of claim 1 , wherein the carbon nanotubes comprise multi-walled carbon nanotubes having a length of 2 μm or less.
7 . The conductive composition of claim 1 , wherein the carbon nanotubes comprise multi-walled carbon nanotubes having a length of from about 2 μm to about 30 μm.
8 . The conductive composition of claim 1 , wherein the carbon nanotubes comprise single-walled carbon nanotubes having a length of from about 1 μm to about 30 μm.
9 . The conductive composition of claim 1 , wherein the carbon nanotubes comprise a mixture of multi-walled carbon nanotubes and single-walled carbon nanotubes wherein:
the multi-walled carbon nanotubes have a length of 2 μm or less; and
the single-walled carbon nanotubes have a length of from about 1 μm to about 30 μm.
10 . The conductive composition of claim 9 , wherein a ratio of multi-walled carbon nanotubes to single-walled carbon nanotubes is from 1:1 to approximately 9:1.
11 . The conductive composition of claim 1 , having an increased fracture toughness by as much as approximately 600%, as compared to a conductive composition without carbon nanotubes.
12 . A screen-printed gridline, comprising:
a cross-sectional triangular shape, comprising:
a top cross-sectional dimension;
a bottom cross-sectional dimension; and wherein:
a ratio of the top cross-sectional dimension to the bottom cross-sectional dimension is 0.8 or less; and
the conductive composition of claim 1 .
13 . A solar cell device, comprising one or more gridlines having the conductive composition of claim 1 .
14 . A screen-printed gridline, comprising:
a cross-sectional triangular shape, comprising:
a top cross-sectional dimension; and
a bottom cross-sectional dimension; and
a conductive composition; and wherein:
a ratio of the top cross-sectional dimension to the bottom cross-sectional dimension is 0.8 or less; and
the conductive composition comprises:
silver particles;
one or more cellulose-based binders;
glass frit;
an organic solvent; and
carbon nanotubes.
15 . The screen-printed gridline of claim 14 , further comprising a cross-sectional height of the screen-printed gridline of from about 15 μm to about 40 μm.
16 . A method of printing gridlines, comprising:
screen-printing one or more gridlines onto a substrate with a conductive composition comprising silver particles, one or more cellulose-based binders, glass frit, organic solvent, carbon nanotubes; and
sintering the gridlines at an elevated temperature.
17 . The method of claim 16 , wherein the substrate is incorporated into a solar cell device.
18 . The method of claim 16 , wherein a viscosity of the conductive composition prior to sintering is from about 300,000 cP to about 50,000 cP at a shear rate of from about 10/sec to about 40/sec.
19 . The method of claim 16 , wherein the carbon nanotubes are present in an amount of from about 0.01% to about 20% by a total weight of the conductive composition.
20 . The method of claim 16 , wherein the carbon nanotubes comprise multi-walled carbon nanotubes having a length of from about 2 μm to about 30 μm.
21 . The method of claim 16 , wherein the carbon nanotubes comprise a mixture of multi-walled carbon nanotubes and single-walled carbon nanotubes wherein:
the multi-walled carbon nanotubes have a length of 2 micron or less; and
the single-walled carbon nanotubes have a length of from about 1 μm to about 30 μm.
22 . The method of claim 21 , wherein a ratio of multi-walled carbon nanotubes to single-walled carbon nanotubes is from 1:1 to approximately 9:1.
23 . The method of claim 21 , wherein a height of the one or more gridlines is from about 15 to about 40 μm.
24 . The method of claim 16 , wherein the one or more gridlines comprises:
a cross-sectional triangular shape, comprising:
a top cross-sectional dimension; and
a bottom cross-sectional dimension; and
a ratio of the top cross-sectional dimension to the bottom cross-sectional dimension is 0.8 or less.