Low Haze Transparent Conductive Electrodes and Method of Making the Same
A transparent conductive electrode comprising metal nanowires and method of making is described, wherein the transparent conductive electrode has a pencil hardness more than 1 H, nanoporous surface having pore sizes less than 25 nm and surface roughness less than 50 nm. The transparent conductive electrode further comprises an index matching layer, having a refractive index between 1.1-1.5 and a thickness between 100-200 nm.
1 . A method of making a conductive film, comprising:
synthesizing and purifying metal nanowires;
suspending purified metal nanowires in a binder free solvent to form dispersion;
coating a thin layer of metal nanowire above a substrate;
heating the substrate with coated layer of nanowire at a temperature 55-150 C to remove the solvent;
applying a layer of sol-gel solution comprising at least one inorganic material above the substrate; and
annealing the film at a temperature between 55-150° C. and releasing the residual solvent and stress in the film.
2 . The method of claim 1 , wherein the metal nanowire is silver nanowire.
3 . The method of claim 1 , wherein the metal nanowire having a length longer than 20 um and a diameter smaller than 60 nm.
4 . The method of claim 1 , wherein the binder free solvent is ethanol, methanol, and isopropanol, or a combination of them.
5 . The method of claim 2 , wherein the concentration of the dispersion is about 0.3% w/v.
6 . The method of claim 1 , wherein the solution comprises an index matching material is a silica sol gel solution.
7 . The method of claim 1 , wherein the substrate is a PET, PET, PEN, COP or glass.
8 . The method of claim 1 , wherein the conductive has a nanoporous surface with pore size less than 25 nm.
9 . The method of claim 1 , wherein the conductive film has pencil hardness more than 1 H.
10 . The method of claim 1 , wherein the conductive film comprises an index matching layer.
11 . The method of claim 10 , further comprising a step of
determining the thickness of the index matching layer by the concentration of the sol gel solution.
12 . The method of claim 1 , further comprising
a process of making nanowires having aspect ratios higher than 500:1, comprising:
heating a solvent at 100-150 degree C.;
adding a nucleating precursor at a (controlled amount and speed, replace with numbers) to the solvent;
reducing metal ions into metal by redox reaction in the solvent;
heating the reaction mixture to allow the reaction to proceed for 4-8 hours;
adding additional metal ions at a controlled rate to maintain the desired ionic concentration; and
quenching the redox reaction with cold water.
13 . The method of claim 12 , wherein the metal nanowires are longer than 50 microns.
14 . The method of claim 12 , wherein the metal nanowires have diameters less than 50 nm.
15 . The method of claim 12 , wherein the solvent is selected from the group of propanol, isopropanol, ethylene glycol, propylene glycol and glycerol, or any combinations thereof.
16 . The method of claim 12 , wherein the nucleating precursor is selected from the group of polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA) and polyethylene oxide (PEO), or any combinations thereof.
17 . The method of claim 12 , wherein the metal nanowires are silver nano wires.
18 . The method of claim 12 , further comprising
precipitating the soluble metal salt with counter ions to form insoluble metal salts, wherein the insoluble metal salt can establish an equilibrium with the soluble metal salt in the solvent.
19 . The method of claim 12 , further comprising
filtering the nanowire solution under pressure.
20 . The method of claim 12 , wherein controlled rate is a rate of less than 1% of total reaction volume/min.