Composition for forming solar cell electrodes and electrodes fabricated using the same
The present invention relates to a composition for forming solar cell electrodes which includes a conductive powder, a glass frit and an organic vehicle, and has a tackiness of about 60% to about 90% represented by Expression 1.
1. A composition for forming solar cell electrodes, the composition comprising a conductive powder, a glass frit, an organic vehicle, and a surface tension modifier having a surface tension of 40 to 60 mN/m, the composition for forming solar cell electrodes having a tackiness of 60% to 90% represented by the following Expression 1:
Tackiness
(
%
)
=
A
-
B
A
×
100
[
Expression
1
]
wherein, in Expression 1, A represents a minimum shear stress value of shear stress measured while detaching a pair of circular plates, from each other, which have a diameter of 25 mm and have been laminated in parallel to each other by a medium of the composition for forming solar cell electrodes, by applying an external force, and B represents a shear stress value at a point at which an instantaneous rate of change of shear stress with respect to a gap between the plates (d (shear stress)/d (gap)) is 0.05.
2. The composition of claim 1 , wherein the composition includes:
50 wt % to 90 wt % of the conductive powder;
1 wt % to 15 wt % of the glass frit;
0.1 to 40 wt % of the surface tension modifier; and
5 wt % to 40 wt % of the organic vehicle.
3. The composition of claim 1 , wherein the surface tension modifier includes one or more of ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, propylene carbonate, formamide, glycerol, and furfural.
4. The composition of claim 1 , wherein the conductive powder includes one or more of 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).
5. The composition of claim 1 , wherein the glass frit includes a leaded glass frit, a lead-free glass frit or mixtures thereof.
6. The composition of claim 1 , wherein the glass fit has an average particle diameter D50 of 0.1 to 5 μm.
7. The composition of claim 1 , further comprising one or more of a dispersant, a plasticizer, a viscosity stabilizer, an anti-foaming agent, a pigment, a UV stabilizer, an antioxidant, and a coupling agent.
8. The composition of claim 1 , wherein the tackiness represented by Expression 1 is in a range of 65% to 90%.
9. A solar cell electrode fabricated using the composition of claim 1 .
10. The composition of claim 1 , to wherein the organic vehicle is a solvent and the solvent includes hexane, toluene, ethyl cellosolve, cyclohexanone, butyl cellosolve, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether, hexylene glycol, terpineol, methyl ethyl ketone, benzyl alcohol, gamma butyrolactone, or ethyl lactate.
11. The composition of claim 1 , wherein the surface tension modifier is included in the composition in an amount of 0.1 wt % to less than 1 wt %.