Method of manufacturing nano-scale LED electrode assembly comprising selective metal ohmic layer
A method of manufacturing a nano-scale LED electrode assembly including a selective metal ohmic layer is disclosed. Specifically, the method can be useful in increasing conductivity between a nano-scale LED device and electrodes and also reducing contact resistance therebetween by depositing a conductive material in a region in which the nano-scale LED device comes in contact with the electrodes so as to improve the contact between the nano-scale LED device and the electrodes, thereby further improving light extraction efficiency of the nano-scale LED device.
1. A method of manufacturing a nano-scale LED electrode assembly comprising a selective metal ohmic layer, comprising:
(1) manufacturing a nano-scale LED electrode assembly by self-aligning nano-scale LED devices on an electrode line comprising first and second electrodes which are formed on a base substrate to be spaced apart from each other;
(2) forming a metal ohmic layer on the nano-scale LED electrode assembly at least including a contact region between nano-scale LED device and electrode line by immersing the nano-scale LED electrode assembly in an electroplating solution and applying a power source to one of the first and second electrodes of the nano-scale LED electrode assembly to perform an electroplating process for a plating time (T 1 ) of 1 to 300 minutes; and
(3) forming a metal ohmic layer on the nano-scale LED electrode assembly by applying a power source to the other electrode, to which the power source is not applied in operation 2, to perform an electroplating process for a plating time T2 satisfying the following Mathematical Expression 1:
1 Minute≤plating time ( T 2 )≤ T 1 [Mathematical Expression 1]
wherein T 1 represents a plating time required for the electroplating process in operation 2.
2. The method of claim 1 , wherein the power source in operation 2 is applied in the form of pulse waves having a voltage of −0.2 to −1.0 V, and the power source of the pulse waves is applied for 0.05 to 30 seconds and paused for 0.05 to 30 seconds.
3. The method of claim 2 , wherein the power source in operation 3 is applied in the form of pulse waves having a voltage of −0.2 to −1.0 V, and the power source of the pulse waves is applied for 0.05 to 30 seconds and paused for 0.05 to 30 seconds.
4. The method of claim 1 , wherein the electroplating solution comprises at least one metal precursor selected from the group consisting of a gold precursor, a silver precursor, a copper precursor, and a platinum precursor metal precursor selected from the group consisting of a gold precursor, a silver precursor, a copper precursor, and a platinum precursor.
5. The method of claim 4 , wherein the electroplating solution comprises the metal precursor at a concentration of 0.001 to 100 mM.
6. The method of claim 1 , wherein operation 1 comprises:
1-1) injecting a dispersion solution comprising a dispersion solvent and nano-scale LED devices toward one surface of the base substrate on which the electrode line comprising the first and second electrodes spaced apart from each other is formed; and
1-2) manufacturing the nano-scale LED electrode assembly by applying the power source to the electrode line to self-align the nano-scale LED devices, wherein the manufactured nano-scale LED electrode assembly is thermally annealed at 600° C. to 1,000° C. for 0.5 to 10 minutes.
7. The method of claim 1 , wherein operation 1 includes either spirally or interdigitatedly disposing the first and second electrodes to be spaced apart from each other.
8. The method of claim 1 , wherein each of the nano-scale LED devices comprises a first electrode layer; a first conductive semiconductor layer formed on the first electrode layer; an active layer formed on the first conductive semiconductor layer; a second conductive semiconductor layer formed on the active layer; and a second electrode layer formed on the second conductive semiconductor layer, and
each of the nano-scale LED devices further comprises an insulating coating film which coats an outer surface thereof.
9. The method of claim 8 , wherein the insulating coating film is applied to cover the entire outer surface of the active layer.
10. The method of claim 9 , wherein outer surfaces of the first and second electrode layers of the nano-scale LED devices are not coated with the insulating coating film.
11. The method of claim 1 , wherein the plating time (T1) in operation 2 is in a range of 10 to 55 minutes.
12. The method of claim 8 , wherein a width X of the first electrode, a width Y of the second electrode, a distance Z between the first electrode and the second electrode adjacent to the first electrode, and a height H of the nano-scale LED devices satisfy the following Relation 1:
0.5 Z≤H<X+Y+ 2 Z [Relation 1]
wherein 100 nm<X≤10 μm, 100 nm<Y≤10 μm, and 100 nm<Z≤10 μm.
13. The method of claim 1 , wherein operation 1 further comprises forming an insulating barrier on the base substrate to surround a region of the electrode line on which the plurality of nano-scale LED devices are positioned.
14. The method of claim 1 , wherein, after operation 3, the manufactured nano-scale LED electrode assembly is thermally re-annealed at 600° C. to 1,000° C. for 0.5 to 10 minutes.