Transparent electrode comprising doped graphene, process of preparing the same, and display device and solar cell comprising the electrode

1. A transparent electrode comprising graphene on at least one surface of a transparent substrate, the graphene doped with a p-dopant,

wherein the p-dopant is an acid having a molecular weight of about 120 or more,

wherein a transmittance variation rate of the doped graphene from before and after the graphene is doped with the p-dopant is about 0.5% or less,

wherein the acid is an inorganic acid or an organic acid,

wherein the organic acid includes at least one of oxalic acid-based organic acid, lactic acid-based organic acid, propionic acid-based organic acid, acetic acid-based organic acid, citric-based organic acid and trifluoroacetate-based organic acid,

wherein the inorganic acid includes at least one of triflate-based inorganic acid, trifluorosulfonimide-based inorganic acid, tetrafluoroborate-based inorganic acid, perchlorate-based inorganic acid, hexafluorophosphate-based inorganic acid, fluoroantimonate-based inorganic acid, silver-based inorganic acid, and tellurium-based inorganic acid, and

wherein the silver-based inorganic acid includes at least one of silver bis(trifluoromethane sulfonimide), silver sulfate, silver thiocyanate, silver hexafluorophosphate, silver hexafluoroantimonate, silver hexafluoroarcenate, silver cyanide, silver tetrafluoroborate, and silver perchlorate.

2. The transparent electrode of claim 1 , wherein

the acid is the inorganic acid, and

carbon atoms contained in the inorganic acid are saturated carbon atoms bonded to each other by single bonds.

3. The transparent electrode of claim 1 , wherein the one of triflate-based inorganic acid, trifluorosulfonimide-based inorganic acid, tetrafluoroborate-based inorganic acid, perchlorate-based inorganic acid, hexafluorophosphate-based inorganic acid, fluoroantimonate-based inorganic acid, and tellurium-based inorganic acid includes at least one of scandium (III) triflate, trifluoromethane sulfonic acid anhydride, bis(trifluoromethane)sulfonimide, bis(trifluoromethane)sulfonimide lithium, bis(pentafluoroethylsulfonyl)imide, nitrosyl bis(trifluoromethane)sulfonimide, trifluoromethanesulfonamide, 2,2,2-trichloroethoxysulfonamide, nitrosyl tetrafluoroborate, nitronium tetrafluoroborate, potassium hexafluorophosphate, hexafluorophosphoric acid, lithium hexafluorophosphate, fluoroantimonate, nitronium hexafluoroantimonate, nitrosodium hexafluoroantimonate, potassium hexafluoroantimonate, fluorosulfuric acid-antimony pentafluoride, teflic acid, and telluric acid.

4. The transparent electrode of claim 1 , wherein

the acid is the organic acid, and

carbon atoms contained in the organic acid are bonded to each other by single bonds.

5. The transparent electrode of claim 1 , wherein

the acid is the organic acid, and

the organic acid includes at least one of oxalic acid-based organic acid, lactic acid-based organic acid, propionic acid-based organic acid, acetic acid-based organic acid, citric acid-based organic acid and trifluoroacetate-based organic acid.

6. The transparent electrode of claim 1 , wherein

the acid is the organic acid, and

the organic acid includes at least one of oxalyl chloride, oxalyl bromide, silver lactate, silver pentafluoropionate, methyl chlorooxoacetate, ethyl chlorooxoacetate, citric acid, lithium citrate, potassium citrate, zinc citrate, cesium trifluoroacetate, ethyl trifluoroacetate, trifluoroacetate anhydride, and silver trifluoroacetate.

7. The transparent electrode of claim 1 , wherein

the acid is the inorganic acid, and

the inorganic acid comprises a metal ion having d-orbitals filled with electrons.

8. The transparent electrode of claim 1 , wherein the molecular weight of the acid is in a range of about 120 to 400.

9. The transparent electrode of claim 1 , wherein the graphene is treated with an acid different from the p-dopant.

10. The transparent electrode of claim 1 , wherein light transmittance of the graphene doped with the p-dopant is about 75% or greater.

11. The transparent electrode of claim 1 , wherein a sheet resistance variation rate after 14 days from the doping of the graphene with the p-dopant is about 20% or less.

12. The transparent electrode of claim 1 , wherein the doped graphene has a sheet resistance reduction rate of about 20% or less, and

wherein the sheet resistance reduction rate is calculated by using the following equation:

Sheet resistance reduction rate (%)=absolute value of {(sheet resistance of graphene right after the graphene is doped with the p -dopant−sheet resistance of graphene before the graphene is doped with the p -dopant)/100}.

13. The transparent electrode of claim 1 , wherein an amount of the p-dopant remains on the surface of the graphene.

14. The transparent electrode of claim 1 , wherein the p-dopant not doped into the graphene forms a surface coating layer on the surface of the transparent substrate.

15. The transparent electrode of claim 1 , wherein the graphene is composed of 1 to 10 stacked layers.

16. The transparent electrode of claim 1 , wherein the graphene is composed of 2 to 10 stacked layers, and the p-dopant is between the graphene layers.

17. The transparent electrode of claim 1 , wherein sheet resistance of the graphene doped with the p-dopant is about 500 Ω/sq. or less.

18. The transparent electrode of claim 1 , wherein the graphene is formed as a mono layer having a size of 1 cm×1 cm, and the amount of the p-dopant (in the graphene mono-layer is in a range of about 0.000025 to 0.0175 mmol.

19. The transparent electrode of claim 1 , wherein the transparent electrode is formed of a flexible material.

20. A solar cell comprising the transparent electrode according to claim 1 .

21. A display device comprising the transparent electrode according to claim 1 .

22. A process of preparing a transparent electrode, the process comprising:

forming a transparent electrode by transferring graphene onto a transparent substrate; and

doping the graphene with a p-dopant solution to obtain doped graphene,

wherein the p-dopant solution is an acid having a molecular weight of about 120 or greater, and

wherein a transmittance variation rate of the graphene from before and after the graphene is doped with the p-dopant solution is about 0.5% or less,

wherein the acid is an inorganic acid or an organic acid,

wherein the organic acid includes at least one of oxalic acid-based organic acid, lactic acid-based organic acid, propionic acid-based organic acid, acetic acid-based organic acid, citric acid-based organic acid and trifluoroacetate-based organic acid,

wherein the inorganic acid includes at least one of triflate-based inorganic acid, trifluorosulfonimide-based inorganic acid, tetrafluoroborate-based inorganic acid, perchlorate-based inorganic acid, hexafluorophosphate-based inorganic acid, fluoroantimonate-based inorganic acid, silver-based inorganic acid, and tellurium-based inorganic acid, and

wherein the silver-based inorganic acid includes at least one of silver bis(trifluoromethane sulfonimide), silver sulfate, silver thiocyanate, silver hexafluorophosphate, silver hexafluoroantimonate, silver hexafluoroarcenate, silver cyanide, silver tetrafluoroborate, and silver perchlorate.

23. The process of claim 22 , wherein the graphene is formed as mono-layers, and a concentration of the p-dopant solution is in a range of about 0.001 to 0.1M per graphene mono-layer.

24. The process of claim 22 , wherein the graphene is formed as mono-layers, and a concentration of the p-dopant solution is in a range of about 0.005 to 0.05M per graphene mono-layer.

25. The process of claim 22 , wherein the graphene is formed as mono-layers, and an amount of the p-dopant solution is in a range of about 0.025 ml to 0.175 ml per graphene mono-layer having a size of 1 cm×1 cm.

26. The process of claim 22 , after the forming the transparent electrode and before the doping the graphene, further comprising:

acid-treating the transparent electrode including the graphene.

27. A thin film comprising graphene on at least one surface of a transparent substrate, the graphene doped with a p-dopant,

wherein the p-dopant is an acid having a molecular weight of about 120 or greater, and

wherein a transmittance variation rate of the graphene from before and after the graphene is doped with the p-dopant is about 0.5% or less,

wherein the acid is an inorganic acid or an organic acid,

wherein the organic acid includes at least one of oxalic acid-based organic acid, lactic acid-based organic acid, propionic acid-based organic acid, acetic acid-based organic acid, citric acid-based organic acid and trifluoroacetate-based organic acid,

wherein the inorganic acid includes at least one of triflate-based inorganic acid, trifluorosulfonimide-based inorganic acid, tetrafluoroborate-based inorganic acid, perchlorate-based inorganic acid, hexafluorophosphate-based inorganic acid, fluoroantimonate-based inorganic acid, silver-based inorganic acid, and tellurium-based inorganic acid, and

wherein the silver-based inorganic acid includes at least one of silver bis(trifluoromethane sulfonimide), silver sulfate, silver thiocyanate, silver hexafluorophosphate, silver hexafluoroantimonate, silver hexafluoroarcenate, silver cyanide, silver tetrafluoroborate, and silver perchlorate.

28. The transparent electrode of claim 1 , wherein the organic acid comprises a metal ion having d-orbitals filled with electrons.