Etching composition and its use in a method of making a photovoltaic cell
View Patent ↗This invention provides a method of making a photovoltaic cell. The method uses an etching composition comprising one or more onium salts selected from the group consisting of iodonium salts and sulfonium and an organic medium to etch the anti-reflection coating. Also provided is a photovoltaic cell made by this method.
1. A method of making a photovoltaic cell, comprising the steps of:
a) providing a silicon substrate with a diffusion layer on the front side of said silicon substrate and an anti-reflection coating superimposed on the surface of said diffusion layer;
b) providing an etching composition, comprising:
i) one or more onium salts selected from the group consisting of iodonium salts and sulfonium salts; and
ii) an organic medium,
wherein said one or more onium salts are dispersed or dissolved in said organic medium;
c) depositing said etching composition onto those portions of said anti-reflection coating that are to be etched; and
d) curing said etching composition to thereby remove said portions of said anti-reflection coating to provide exposed surface of said diffusion layer to serve as the contact for a front side electrode.
2. The method of claim 1 , wherein said iodonium salts are diaryl iodonium salts and said sulfonium salts are triaryl sulfonium salts.
3. The method of claim 2 , said etching composition further comprising a photoinitiator whereby said etching composition is UV curable and wherein said curing is accomplished by exposing said etching composition to UV light.
4. The method of claim 2 , wherein said curing is accomplished by exposing said etching composition to a temperature of from 300° C. to 900° C.
5. The method of claim 1 , further comprising the steps of:
e) depositing a front side electrode-forming paste onto said exposed surface of said diffusion layer; and
f) firing said front side electrode-forming paste to form said front side electrode.
6. The method of claim 5 , wherein said iodonium salts are diaryl iodonium salts and said sulfonium salts are triaryl sulfonium salts.
7. The method of claim 6 , said etching composition further comprising a photoinitiator whereby said etching composition is UV curable and wherein said curing is accomplished by exposing said etching composition to UV light.
8. The method of claim 6 , wherein said curing is accomplished by exposing said etching composition to a temperature of from 300° C. to 900° C.