Composition for solar cell electrodes and electrode fabricated using the same
A composition for solar cell electrodes includes a conductive powder, a glass frit, an organic vehicle and a thixotropic agent, and has a first thixotropic index (TI I) of about 1.5 to about 4 as represented by the following Equation 1, and a second thixotropic index (TI II) of about 4 to about 8 as represented by the following Equation 2, both the first thixotropic index and the second thixotropic index being measured at 23° C. by a rotary viscometer. [Equation 1] TI I=(viscosity at 1 rpm/viscosity at 10 rpm) [Equation 2] TI II=(viscosity at 10 rpm/viscosity at 100 rpm).
1. A composition for a solar cell electrode, the composition comprising:
a conductive powder;
a glass frit;
an organic vehicle; and
a thixotropic agent, wherein the thixotropic agent includes at least one selected from an amine compound, a castor oil compound, a carbon black compound, a fumed silica compound, and an organo-clay compound,
wherein a combination of the organic vehicle and the thixotropic agent, and amounts thereof, are selected such that the composition-has a first thixotropic index (TI I) of 1.5 to 2 as represented by the following Equation 1, and a second thixotropic index (TI II) of about 4 to about 8 as represented by the following Equation 2, such that the first thixotropic index is lower than the second thixotropic index, both the first thixotropic index and the second thixotropic index being measured at 23° C. by a rotary viscometer
TI I=(viscosity at 1 rpm/viscosity at 10 rpm) [Equation 1]
TI II=(viscosity at 10 rpm/viscosity at 100 rpm) [Equation 2].
2. The composition according as claimed in claim 1 , wherein the composition includes:
about 50 wt % to about 90 wt % of the conductive powder;
about 1 wt % to about 15 wt % of the glass frit;
about 5 wt % to about 40 wt % of the organic vehicle; and
about 0.01 wt % to about 2 wt % of the thixotropic agent.
3. The composition as claimed in claim 1 , wherein the conductive powder includes at least one selected from silver (Ag), gold (Au), palladium (Pd), platinum (Pt), copper (Cu), chromium (Cr), cobalt (Co), aluminum (Al), tin (Sn), lead (Pb), zinc (Zn), iron (Fe), iridium (Ir), osmium (Os), rhodium (Rh), tungsten (W), molybdenum (Mo), nickel (Ni), and indium tin oxide (ITO).
4. The composition as claimed in claim 1 , wherein the glass frit includes a leaded glass frit, a lead-free glass frit, or a mixture thereof.
5. The composition as claimed in claim 1 , wherein the glass frit has an average particle diameter (D50) of about 0.1 μm to about 5 μm.
6. The composition as claimed in claim 1 , wherein the composition includes at least one additive selected from a dispersant, a plasticizer, a viscosity stabilizer, an anti-foaming agent, a UV stabilizer, an antioxidant, and a coupling agent.
7. A solar cell electrode produced from the composition for solar cell electrodes according to claim 1 .