Nanostructure network and method of fabricating the same
Provided are a nanostructure network and a method of fabricating the same. The nanostructure network includes nanostructures having a poly-crystalline structure formed by self-assembly of the nanostructures. The method includes preparing a nanostructure solution in which nanostructures are dispersed in a first solvent, forming a nanostructure ink by adding the nanostructure solution into a second solvent having a viscosity higher than that of the first solvent, coating a surface of a substrate with the nanostructure ink, and forming a nanostructure network by evaporating the first solvent and the second solvent included in the nanostructure ink coated on the substrate.
1. A method of fabricating a nanostructure network, the method comprising:
preparing a nanostructure solution in which nanostructures are dispersed in a first solvent;
forming a nanostructure ink by adding the nanostructure solution into a second solvent having a viscosity higher than that of the first solvent and an admixture for mixing the first solvent and the second solvent;
coating a surface of a substrate with the nanostructure ink; and
forming a nanostructure network by evaporating the first solvent and the second solvent included in the nanostructure ink coated on the substrate,
wherein the coating of the surface of the substrate with the nanostructure ink comprises:
generating a coating layer in a liquid state on the substrate; and
dividing the coating layer into a plurality of first droplets spaced apart from each other, and
wherein the forming of the nanostructure network comprises:
evaporating the admixture prior to the first solvent and the second solvent from the first droplet to form a second droplet;
evaporating the first solvent prior to the second solvent from the second droplet to form a third droplet; and
evaporating the second solvent from the third droplet.
2. The method of claim 1 , wherein a vapor pressure of the first solvent is higher than a vapor pressure of the second solvent.
3. The method of claim 1 ,
wherein a vapor pressure of the admixture is higher than vapor pressures of the first solvent and the second solvent.
4. The method of claim 1 , wherein the second droplet includes a central portion and a peripheral portion,
wherein a concentration of the first solvent is lower than a concentration of the second solvent in the central portion,
wherein a concentration of the first solvent is higher than a concentration of the second solvent in the peripheral portion, and
wherein a concentration of the nanostructures in the peripheral portion is higher than a concentration of the nanostructures in the central portion.
5. The method of claim 1 , wherein an affinity between the first solvent and the nanostructures is higher than an affinity between the second solvent and the nanostructures.
6. The method of claim 5 , wherein the evaporating of the admixture prior to the first solvent and the second solvent from the first droplet to form the second droplet comprises:
concentrating the nanostructures to an edge of the second droplet by a difference in affinity between the first solvent and the second solvent for the nanostructures.
7. The method of claim 1 , wherein the nanostructures are self-assembled into a poly-crystalline structure while forming a plurality of cell shapes, thereby forming the nanostructure network, and
wherein an average size of the plurality of cells is adjusted by a content or the viscosity of the second solvent.
8. The method of claim 7 , wherein the average size of the plurality of cells increases as the content of the second solvent increases, and the average size of the plurality of cells decreases as the content of the second solvent decreases.
9. The method of claim 7 , wherein the average size of the plurality of cells decreases as the viscosity of the second solvent increases, and the average size of the plurality of cells increases as the viscosity of the second solvent decreases.
10. The method of claim 1 , further comprising:
pretreating the surface of the substrate to convert the surface into a hydrophilic surface, before the coating of the surface of the substrate with the nanostructure ink.
11. The method of claim 10 , wherein the surface of the substrate is pretreated with oxygen plasma.
12. The method of claim 1 , wherein the second solvent includes α-terpineol, cyclohexanol, or 1-dodecanol.
13. The method of claim 1 , wherein the coating of the surface of the substrate with the nanostructure ink is performed using a slot die, a Meyer rod, or a doctor blade.
14. The method of claim 1 , wherein the nanostructures are formed of silver, copper, gold, ITO, ATO, or FTO.
15. The method of claim 1 , wherein the nanostructures have a nanowire structure or a core-shell structure.
16. The method of claim 1 , wherein the nanostructures comprise silver nanowires.
17. The method of claim 1 , wherein the substrate is transparent.