Metal nanostructured networks and transparent conductive material
Metal nanowires, such as silver nanowires coated on a substrate were sintered together to form fused metal nanowire networks that have greatly improved conductivity while maintaining good transparency and low haze. The method of forming such a fused metal nanowire networks are disclosed that involves exposure of metal nanowires to various fusing agents on a short timescale. The resulting sintered network can have a core-shell structure in which metal halide forms the shell. Additionally, effective methods are described for forming patterned structure with areas of sintered metal nanowire network with high conductivity and areas of un-sintered metal nanowires with low conductivity. The corresponding patterned films are also described. When formed into a film, materials comprising the metal nanowire network demonstrate low sheet resistance while maintaining desirably high levels of optical transparency with low haze, making them suitable for transparent electrode, touch sensors, and other electronic/optical device formation.
1. A precursor ink comprising a solvent, at least about 0.01 weight percent metal nanowires and from about 0.5 mM to about 50 mM halide anions.
2. The precursor ink of claim 1 having from about 0.025 to about 2 weight percent metal nanowires.
3. The precursor ink of claim 1 having from about 0.25 mM to about 10 mM halide anions.
4. The precursor ink of claim 1 wherein the metal nanowires are silver nanowires.
5. The precursor ink of claim 4 wherein the silver nanowires have an average diameter of no more than about 75 nm and a length of at least about 5 microns.
6. The precursor ink of claim 1 wherein the solvent comprises alcohol.
7. The precursor ink of claim 1 wherein the solvent comprises water.
8. The precursor ink of claim 1 wherein the halide ions comprise fluoride ions.
9. The precursor ink of claim 8 further comprising silver ions (Ag + ).
10. The precursor ink of claim 1 further comprising from about 0.5 mM to about 50 mM silver ions (Ag + ).
11. The precursor ink of claim 1 wherein the halide anions are fluoride ions with a concentration from about 1 mM to about 25 mM.
12. A method for forming a transparent conductive film, the method comprising:
depositing a precursor ink of claim 1 ; and
drying the deposited ink to form the transparent conductive film.
13. The method of claim 12 wherein the depositing comprises slot-die coating.
14. The method of claim 12 wherein the transparent conductive film comprises a fused metal nanostructured network.
15. The method of claim 14 wherein the transparent conductive film has a sheet resistance of no more than 100 ohms/sq.
16. The method of claim 14 wherein the transparent conductive film has a transmittance of at least about 90% and a haze of no more than 0.5%.
17. The method of claim 12 wherein the transparent conductive film has a metal loading from about 5 microgram g/cm 2 (μg/cm 2 ) to about 1 mg/cm 2 .
18. The method of claim 12 wherein coating and drying are performed in a roll-to-roll configuration.
19. The method of claim 12 wherein the precursor ink comprises silver fluoride.
20. The method of claim 12 wherein the precursor ink comprises silver nanowires with a fluoride concentration from about 1 mM to about 25 mM and wherein the solvent comprises water.