Thin and uniform silver nanowires, method of synthesis and transparent conductive films formed from the nanowires
Highly uniform and thin silver nanowires are described having average diameters below 20 nm and a small standard deviation of the diameters. The silver nanowires have a high aspect ratio. The silver nanowires can be characterized by a small number of nanowires having a diameter greater than 18 nm as well as with a blue shifted narrow absorption spectrum in a dilute solution. Methods are described to allow for the synthesis of the narrow uniform silver nanowires. Transparent conductive films formed from the thin, uniform silver nanowires can have very low levels of haze and low values of ΔL*, the diffusive luminosity, such that the transparent conductive films can provide little alteration of the appearance of a black background.
1. A transparent electrically conductive structure comprising:
a transparent substrate and a first sparse metal conductive layer over a first surface of the transparent substrate wherein the first sparse metal conductive layer comprises fused metal nanostructured network and a polysaccharide and wherein the sparse metal conductive layer is formed form an ink comprising about 0.01 to about 1 weight percent metal nanowires and from about 0.1 to about 2.5 weight percent polysaccharide,
wherein the transparent electrically conductive structure has a sheet resistance of no more than about 100 ohms/sq, a total transmittance of visible light of at least about 90% and a haze of no more than about 0.60%, and
wherein the value of ΔL* obtained in a diffuse reflection configuration on a substrate with a black surface is no more than a value of 2.0, ΔL*=L* of the electrically conductive structure minus L* of the structure without the sparse metal conductive layer.
2. The transparent electrically conductive structure of claim 1 wherein the polysaccharide comprises a cellulose-based polymer.
3. The transparent electrically conductive structure of claim 1 further comprising a polymer overcoat on the first sparse metal conductive layer.
4. The transparent electrically conductive structure of claim 3 wherein the transparent electrically conductive structure has a sheet resistance of no more than about 75 ohms/sq, a total transmittance of visible light of at least about 91% and a haze of no more than about 0.35%.
5. The transparent electrically conductive structure of claim 4 having a haze of no more than 0.40% and a ΔL* associated with the first sparse metal conductive layer and the polymer overcoat of no more than 1.5.
6. The transparent electrically conductive structure of claim 4 wherein the polymer overcoat comprises an acrylate polymer.
7. The transparent electrically conductive structure of claim 1 wherein the transparent electrically conductive structure has a sheet resistance of no more than about 75 ohms/sq, a total transmittance of visible light of at least about 91% and a haze of no more than about 0.40%.
8. The transparent electrically conductive structure of claim 1 further comprising:
a second sparse metal conductive layer over a second surface of the substrate opposite the first surface,
wherein the second surface of the transparent electrically conductive structure has a sheet resistance of no more than about 100 ohms/sq.
9. The transparent electrically conductive structure of claim 8 wherein each surface of the transparent electrically conductive structure has a sheet resistance from about 60 to about 90 ohms/sq.
10. The transparent electrically conductive structure of claim 8 wherein each surface of the transparent electrically conductive structure has a sheet resistance from about 40 to about 60 ohms/sq.
11. The transparent electrically conductive structure of claim 1 wherein the fused metal nanostructured network comprises nanowire segments having an average diameter of no more than about 20 nm and a standard deviation of the diameter of no more than about 2.5 nm.
12. The transparent electrically conductive structure of claim 11 wherein the nanowire segments have an average diameter of no more than about 18 nm.
13. The transparent electrically conductive structure of claim 11 wherein the nanowire segments have an average diameter of no more than about 16 nm.
14. The transparent electrically conductive structure of claim 11 wherein the nanowire segments have a standard deviation of the diameter of no more than about 2.25 nm.
15. The transparent electrically conductive structure of claim 11 wherein the nanowire segments have a standard deviation of the diameter of no more than about 2.0 nm.
16. The transparent electrically conductive structure of claim 11 wherein no more than 25% of the nanowire segments have a diameter greater than 18 nm.
17. The transparent electrically conductive structure of claim 11 wherein no more than about 10% of the nanowire segments have a diameter greater than 18 nm.
18. The transparent electrically conductive structure of claim 11 wherein the nanowire segments have a noble metal coating.
19. The transparent electrically conductive structure of claim 1 having a b* value of no more than about 1.0.
20. A transparent electrically conductive structure comprising:
a transparent substrate and a first sparse metal conductive layer over a first surface of the transparent substrate,
wherein the transparent electrically conductive structure has a sheet resistance of no more than about 100 ohms/sq, a total transmittance of visible light of at least about 90%, a b* value of no more than about 1.0, and a haze of no more than about 0.60%, and
wherein the value of ΔL* obtained in a diffuse reflection configuration on a substrate with a black surface is no more than a value of 2.0, ΔL*=L* of the electrically conductive structure minus L* of the structure without the sparse metal conductive layer.