Method of tuning work function of metal nanostructure-based transparent conductor
View Patent ↗The present disclosure relates to methods for tuning the work function of a metal nanostructure-based conductive film by forming a dipole surface layer on individual metal nanostructures.
1. A method for adjusting work function of a metal nanostructure-based conductive film, the method comprising:
providing a plurality of metal nanostructures, each metal nanostructure having an outer surface; and
forming a dipole surface layer on the outer surface of the metal nanostructure, wherein the dipole surface layer includes a plurality of dipole ligands, and wherein the dipole ligands are present at about 10 −6 to 10 −4 moles per m 2 surface area of the metal nanostructures.
2. The method of claim 1 wherein forming the dipole surface layer on the outer surface of the metal nanostructure includes:
forming an ink composition that comprises the plurality of metal nanostructures and the plurality of dipole ligand, and
coating the ink composition on a substrate to provide the conductive film.
3. The method of claim 1 , wherein adjusting work function includes increasing the work function by about 0.8-1.2 eV as compared to a conductive film form of metal nanostructures without a dipole surface layer.
4. The method of claim 1 , wherein the dipole ligand is a polar molecule.
5. The method of claim 4 wherein the polar molecule is a surfactant.
6. The method of claim 5 wherein the surfactant is an anionic fluorosurfactant.
7. The method of claim 1 wherein the dipole ligand is lithium carboxylate anionic fluorosurfactant.
8. An ink composition comprising:
a plurality of metal nanowires, and
a plurality of dipole ligands, wherein the dipole ligands are present at about 10 −6 to 10 −4 moles per m 2 surface area of the metal nanostructures.
9. The ink composition of claim 8 wherein the dipole ligands are present at about 10 −5 to 10 −4 moles per m 2 surface area of the metal nanostructures.
10. The ink composition of claim 8 wherein the metal nanostructures are silver nanowires.
11. The ink composition of claim 8 wherein the dipole ligand is an anionic fluorosurfactant.
12. The ink composition of claim 11 wherein the anionic fluorosurfactant is a lithium carboxylate anionic fluorosurfactant.
13. The ink composition of claim 8 , further comprising: a surfactant, wherein a weight ratio of the plurality of the metal nanowires and the surfactant is in a range of 560:1 to 5:1.
14. The ink composition of claim 8 , further comprising a viscosity modifier.
15. The ink composition of claim 14 wherein the viscosity modifier is HPMC.
16. An organic light emitting diode (OLED) device comprising:
a cathode,
an anode, and
an organic emissive stack disposed between the cathode and the anode,
wherein the anode includes a conductive film of a plurality of metal nanostructures, each metal nanostructure having an outer surface and a dipole surface layer disposed on the outer surface, and wherein the dipole surface layer includes a plurality of dipole ligands, and wherein the dipole ligands are present at about 10 −6 to 10 −4 moles per m 2 surface area of the metal nanostructures.
17. The OLED device of claim 16 , wherein the dipole ligands are present at 10 −5 to 10 −4 moles per m 2 surface area of the metal nanostructures.
18. The OLED device of claim 16 , wherein the dipole ligands are anionic surfactants.
19. The OLED device of claim 16 , wherein the anode has a work function of 5.2-5.7 eV.
20. A method for adjusting work function of a metal nanostructure-based conductive film, the method comprising:
providing a plurality of metal nanostructures, each metal nanostructure having an outer surface; and
forming a dipole surface layer on the outer surface of the metal nanostructure, wherein the dipole surface layer includes a plurality of dipole ligands, wherein adjusting work function includes increasing the work function by about 0.8-1.2 eV as compared to a conductive film form of metal nanostructures without a dipole surface layer.
21. The method of claim 20 wherein the dipole ligand is a fluorosurfactant.
22. A transparent electrode comprising: a conductive film having a plurality of metal nanostructures, each metal nanostructure having an outer surface and a dipole surface layer disposed on the outer surface, wherein the dipole surface layer includes a plurality of dipole ligands and wherein the transparent electrode has a work function of 5.2-5.7 eV.
23. An organic light emitting diode (OLED) device comprising the transparent electrode of claim 22 .