Photosensitive ink compositions and transparent conductors and method of using the same

1. A method, comprising:

forming a thin film of interconnecting conductive nanostructures on a substrate, wherein the forming comprises:

depositing an ink composition on the substrate, wherein the ink composition comprises a plurality of conductive nanostructures, a binding material, a photosensitive compound, and a polar solvent; and

removing the polar solvent, wherein:

the photosensitive compound is a photoinitiator present at about 0.005% to 0.01% by weight of the ink composition, and

the photoinitiator comprises a mixture of oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester and oxy-phenyl-acetic acid 2-[2-hydroxy-ethoxy]-ethyl ester; and

exposing a first portion of the thin film to an ultra violet (UV) light source to cause the binding material in the first portion of the thin film to crosslink.

2. The method of claim 1 , further comprising placing a mask above the thin film prior to exposing the first portion of the thin film to the UV light source, wherein the mask comprises an opening that overlies the first portion of the thin film.

3. The method of claim 1 , further comprising dissolving a second portion of the thin film that is not exposed to the UV light source.

4. The method of claim 1 , wherein the binding material is a crosslinkable polymer selected from the group consisting of polyvinylpyrrolidone, polyvinyl alcohol, polyacrylamides, polyacrylates, polyethylene oxides, polyethylene imine, anionic and cationic polyelectrolytes, poly (2-ethyl-2-oxazoline), hydroxypropylmethyl cellulose, hydroxypropylmethyl cellulose phthalate, hydroxypropyl cellulose, hydroxybutylmethyl cellulose, ethylhydroxyethyl cellulose, sodium carboxymethyl-hydroxyethyl cellulose, and carboxymethylethyl cellulose.

5. The method of claim 1 , wherein a ratio of the binding material to the conductive nanostructures is about 5 to about 0.000625.

6. The method of claim 1 , wherein a ratio of the binding material to the conductive nanostructures is about 1.

7. The method of claim 1 , wherein the binding material is hydroxypropylmethyl cellulose.

8. The method of claim 1 , wherein:

the polar solvent is a protic solvent having a polarity index of at least 4, and

the polar solvent is about 94.5% to 99.0% by weight of the ink composition.

9. The method of claim 8 , wherein the polar solvent is water, monohydric alcohol or polyhydric alcohol.

10. The method of claim 8 , wherein the polar solvent is polypropylene glycol monomethyl ether.

11. The method of claim 1 , wherein:

the plurality of conductive nanostructures are metal nanowires, and

the metal nanowires are about 0.01% to 10% by weight of the ink composition.

12. The method of claim 11 , wherein the metal nanowires are more than 10 μm in length and less than 100 nm in diameter.

13. The method of claim 1 , wherein a ratio of the photoinitiator to the binding material is about 0.01 to 0.1.

14. The method of claim 1 , wherein the photoinitiator is about 0.01% by weight of the ink composition.

15. The method of claim 1 , wherein:

the ink composition further comprises a surfactant, and

the surfactant is about 0.0025% to 0.1% by weight of the ink composition.

16. The method of claim 1 , further comprising:

applying a second polar solvent after exposing the first portion of the thin film to the UV light source, wherein the second polar solvent dissolves a second portion of the thin film different than the first portion of the thin film; and

drying the thin film after applying the second polar solvent.

17. The method of claim 16 , wherein the polar solvent and the second polar solvent have a same material composition.

18. The method of claim 16 , wherein drying the thin film comprises:

drying the thin film in a nitrogen atmosphere for at a temperature of about 180° C.

19. The method of claim 1 , wherein:

the polar solvent comprises propylene glycol monomethyl ether,

the binding material comprises hydroxypropylmethyl cellulose,

the ink composition comprises a surfactant, and

the surfactant comprises an octylphenol ethoxylate.

20. A method, comprising:

forming a thin film of interconnecting conductive nanostructures on a substrate, wherein the forming comprises:

depositing an ink composition on the substrate, wherein the ink composition comprises a plurality of conductive nanostructures, a binding material, a photosensitive compound, and a polar solvent; and

removing the polar solvent, wherein:

the photosensitive compound is a photoinitiator present at about 0.005% to 1% by weight of the ink composition, and

the photoinitiator is an onium salt that is thermally degradable and is capable of causing structural damage to the conductive nanostructures when heated; and

exposing a first portion of the thin film to an ultra violet (UV) light source to cause the binding material in the first portion of the thin film to crosslink.

21. The method of claim 20 , wherein:

the binding material is a crosslinkable polymer, and

the polar solvent has a polarity index of at least 4.

22. The method of claim 21 , wherein:

the plurality of conductive nanostructures are metal nanowires, and

the metal nanowires are about 0.01% to 10% by weight of the ink composition.

23. The method of claim 20 , wherein:

the plurality of conductive nanostructures are metal nanowires, and

the metal nanowires are about 0.01% to 10% by weight of the ink composition.