KR20140126842A - Method for forming transparent electrode and the transparent electrode, light-emitting diode and optical device including it - Google Patents

Abstract

The present invention provides a method for forming a metal layer capable of performing a layer-by-layer growth at a thin thickness and forming a transparent electrode by successively stacking a contact layer, a metal layer, and a metal oxide layer on a support substrate or an optical device. According to the present invention, the transparent electrode of high performance, low surface resistance, and high light transmission is formed without additional process installation and steps by the connection of an Ag thin film between domains at a thin thickness by an addictive (dopant) like Mg and Ti. Thereby, an optical device with high performance is manufactured.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of forming a transparent electrode, a transparent electrode, and a light emitting diode and an optical device including the transparent electrode,

The present invention relates to a transparent electrode forming method, a transparent electrode, and a light emitting diode and an optical element including the transparent electrode. More particularly, the present invention relates to a transparent electrode forming a contact layer, a metal layer and a metal oxide layer on a support substrate or an optical element A transparent electrode, and a light emitting diode and an optical element including the same.

White light source GaN (Gallium Nitride) LED has long life, small size, light weight, strong directivity of light, low voltage drive, and it does not require preheating time and complicated drive circuit and is resistant to shock and vibration. System, it is expected to replace incandescent lamps, fluorescent lamps, mercury lamps and conventional white light sources within the next 10 years, and many studies are underway.

In order to replace the conventional mercury lamp or fluorescent lamp as a white light source, the GaN LED needs to increase the amount of light emitted per unit price by improving the luminous efficiency and lowering the manufacturing cost.

One of the ways to solve this problem is to emit light to the outside without loss of light through formation of a transparent electrode having excellent performance.

In addition, high-performance transparent electrodes are indispensable for optical devices in various fields such as organic light emitting diodes and solar cells.

As the transparent electrode, ITO having high transparency and excellent electric conductivity is widely used. However, since ITO is manufactured by a high energy process such as sputtering or electron beam deposition (e-beam), a semiconductor material It may damage the organic layer material.

In order to solve such a problem, Korean Patent Publication No. 2007-0069314 discloses a method of forming a thin film using a Ca / Ag electrode, a Ba / Ag electrode, and a Mg / Ag electrode structure in which an alkali metal and Ag capable of thermal deposition are bonded, Discloses a method of manufacturing a transparent electrode having electrical conductivity characteristics.

However, in the case of such an alkali metal, since it is vulnerable to penetration of moisture and oxygen, lifetime characteristics and stability of the device may be deteriorated.

Korean Patent Laid-Open Publication No. 2009-0105316 discloses a transparent electrode structure of a metal oxide-metal composite structure, which forms a multilayer thin film of a metal oxide / metal / metal oxide by a thermal deposition method, Thereby forming a transparent electrode having conductivity characteristics.

However, since the Fermi level of the metal oxide does not coincide with the level of the semiconductor layer, the charge injection characteristic is lowered, thereby decreasing the efficiency of the device. In this case, .

Further, in order to obtain a transparent electrode having a low sheet resistance together with a high transmittance, an Ag system is mainly used as a metal layer material in a multi-layered metal oxide-metal composite structure.

That is, a high-performance transparent electrode must have a high transmittance and a low sheet resistance at the same time, but there is a problem that a low sheet resistance with a high transmittance has an inverse relationship with a thickness of a metal layer.

As the material of this metal layer, Ag, which is the metal having the lowest sheet resistance, is used, but the Ag-based material has a domain which is lowered due to island growth at a thin thickness and eventually has a high sheet resistance.

More specifically, in order to obtain a transparent electrode having a high transmittance of 80% or more by using the Ag, it is necessary to use the Ag at a thickness of 100 angstroms or less. In this case, the island- There has been a problem of a sudden increase.

Korean Patent Publication No. 2007-0069314 (Jul. 03, 2007) Korean Patent Publication No. 2009-0105316 (October 07, 2009)

The present invention has been researched and developed to solve the above-mentioned problems, and it is an object of the present invention to provide a transparent electrode having a low electrical resistance and high light transmittance and easy charge injection into a light emitting layer by using a multilayer thin film structure of a contact layer / metal layer / A transparent electrode, and a light emitting diode and an optical element including the same.

Another object of the present invention is to provide a method of forming a transparent electrode having a low sheet resistance while maintaining the thickness of a metal layer at 100 Å or less in a multilayer transparent electrode structure, a transparent electrode, and a light emitting diode and an optical element including the same. There is a purpose.

In order to accomplish the above object, the present invention provides a method of manufacturing a thin-film solar cell, comprising: laminating a contact layer, a metal layer, and a metal oxide layer on a support substrate or an optical element in sequence, wherein a small amount of dopant is added to the Ag thin film constituting the metal layer, And changes from island growth mode to layer-by-layer (LbL) growth mode.

According to the present invention, since the growth mode of the Ag thin film is changed from the island growth mode to the layer-by-layer (LbL) growth mode through a small amount of additive, The present invention also provides a method of forming a metal layer having a low sheet resistance by connecting the domains to each other in a thick metal layer, thereby achieving high light extraction efficiency and current injection smoothly.

FIGS. 1A to 1C are views showing structures of an inorganic semiconductor light emitting diode, an organic light emitting diode, and a solar cell having a transparent electrode according to the present invention.
2A and 2B are views illustrating a structure of a transparent electrode according to an embodiment of the present invention.
3A and 3B are graphs showing sheet resistance and transmittance according to the thickness of an Ag thin film when Ag is used as a metal layer material in a transparent electrode formed according to an embodiment of the present invention.
FIGS. 4A to 4C show the surface morphology and sheet resistance of the Ag thin film deposited according to the embodiment of the present invention, and show the results of comparison according to the presence or absence of the dopant.
FIG. 5 shows X-ray diffraction results when an Ag thin film is deposited according to an embodiment of the present invention, and shows a result of comparison according to presence or absence of a dopant.
FIG. 6 is a graph showing refractive indexes and absorption coefficients of an Ag thin film according to dopants added according to an embodiment of the present invention. FIG.
FIG. 7 shows the thicknesses of the Ag metal layer and the MoO ₃ metal oxide layer having the highest transmittance at 450 nm according to the present invention, and shows a comparison result according to the presence or absence of the dopant.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Also, when a part is referred to as "including " an element, it does not exclude other elements unless specifically stated otherwise.

In the following figures, the size or thickness of the film (s) or regions is exaggerated for clarity of description.

FIGS. 1A to 1C are views showing structures of an inorganic semiconductor light emitting diode, an organic light emitting diode, and a solar cell having a transparent electrode according to the present invention.

The inorganic semiconductor light emitting diode 10 of FIG. 1A is formed by sequentially stacking an n-type inorganic semiconductor 12, an inorganic light emitting layer 13, a p-type inorganic semiconductor 14 and a transparent electrode 15 on a substrate 11.

The organic light emitting diode 20 of FIG. 1B is formed by sequentially laminating an anode 22, an organic semiconductor layer 23 and a transparent electrode 24 on a substrate 21, An injection layer 23a, a hole transporting layer 23b, an organic light emitting layer 23c, a hole blocking layer 23d and an electron transporting layer 23e are stacked in this order.

The solar cell 30 of FIG. 1C is formed by sequentially stacking a light scattering layer 32, a transparent electrode 33, a photoactive layer 34, and an electrode 35 on a substrate 31.

2A and 2B are views illustrating a structure of a transparent electrode according to an embodiment of the present invention.

2A, a transparent electrode 50 is formed by sequentially laminating a contact layer 52, a metal layer 54, and a metal oxide layer 56 on a support layer 40.

First, a contact layer 52 is formed on the support layer 40 by using a thermal deposition process, or by an electron beam deposition process or a sputter process.

Here, the supporting layer 40 may be the p-type inorganic semiconductor 42 shown in FIG. 1A, the organic semiconductor layer 23 shown in FIG. 1B, and the light scattering layer 32 shown in FIG. 1C.

The contact layer 52 includes at least one selected from the group consisting of Ni, Ti, Pt, and Cr.

If the thickness of the contact layer 52 is less than 1 angstrom, it is difficult to form a contact layer. If the thickness of the contact layer 52 is more than 10 angstroms, the transmittance is drastically lowered, and the thickness of the contact layer 52 is preferably 1 to 10 angstroms.

Next, a metal layer 54 is formed on the contact layer 52 using a thermal deposition process, or is formed using an electron beam deposition process or a sputter process.

At this time, the metal layer 54 is made of Ag, a dopant material such as Mg, Ti, Cu, In, or an alloy thereof.

When the thickness of the metal layer 54 is less than 10 angstroms, it is difficult to have a high transmittance due to the refractive index matching. When the thickness exceeds 100 angstroms, the transmittance of the metal layer 54 is rapidly decreased, and the thickness of the metal layer 54 is preferably 10 to 100 angstroms.

If the amount of the dopant added to the Ag is less than 0.1 wt.%, It is difficult to form a continuous Ag thin film layer by the dopant. When the amount of the dopant is more than 10 wt.%, The refractive index and the absorption coefficient of the Ag- It is difficult to have a high transmittance due to the refractive index matching, and the amount of the dopant added to Ag is preferably 0.1 to 10 wt.%.

The sheet resistance of the metal layer 54 is 10 Ω / sq or less at a thickness of 100 Å or less.

Next, a metal oxide layer 56 is formed on the metal layer 54 using a thermal deposition process, or is formed using an electron beam deposition process or a sputter process.

The metal oxide layer 56 may include at least one selected from the group consisting of MoOx, WOx, VOx, NiOx, and RuOx.

Also, the oxygen content (x) of the metal oxide is 1 to 10.

<Examples>

In the specific embodiment of the transparent electrode forming method described above, a gallium nitride-based semiconductor layer is used as the support layer 40.

In order to fabricate a gallium nitride semiconductor substrate, a gallium nitride semiconductor deposited on a sapphire substrate was dipped in an aqueous hydrochloric acid solution (hydrochloric acid: deionized water = 1: 1) for 10 minutes using metalorganic chemical vapor deposition (MOCVD) Washed, and dried with nitrogen.

Ag, Ag (Mg), and Ag (Ti) are then deposited on the gallium nitride semiconductor layer to a thickness of 100 Å by electron beam evaporation to form the metal layer 54.

At this time, the metal layer 54 is deposited at a degree of vacuum of 10 ^-6 Torr or less and deposited at a rate of 1 Å / s.

The Ag (Mg) and Ag (Ti) alloys are formed by adding 3 wt.% Mg and Ti to Ag in a crucible and then irradiating with electron beam.

Thereafter, a metal oxide layer 56 is formed by depositing MoO ₃ to 35 nm using a thermal deposition method.

At this time, the metal oxide layer 56 is deposited at a vacuum degree of 10 ^-6 Torr or less and is deposited at a rate of 0.8 Å / s.

In FIG. 2B, another metal oxide layer 58 is formed between the contact layer 52 and the metal layer 54 of FIG. 2A using a thermal deposition process, or by an electron beam deposition process or a sputter process.

2A and 2B, the transparent electrode 50 having the metal oxide layer 56 stacked on the metal layer 54 has an impedance value corresponding to a zero reflection condition, Can be improved.

3A and 3B are graphs showing sheet resistance and transmittance according to the thickness of an Ag thin film when Ag is used as a metal layer material in a transparent electrode formed according to an embodiment of the present invention.

In the case of the Ag thin film not containing the dopant in FIG. 3A, since the thin film growth proceeds by the island growth method rather than the LbL growth, the sheet resistance is higher than 10? / Sq at the very thin thickness, .

However, in FIG. 3B, as the thickness of the Ag thin film increases, the light transmittance sharply decreases from about 78% to less than 20% at a wavelength of 450 nm.

FIGS. 4A to 4C show the surface morphology and sheet resistance of the Ag thin film deposited according to the embodiment of the present invention, and show the results of comparison according to the presence or absence of the dopant.

In FIG. 4A, when the Ag thin film is deposited to 100Å, the shape of the Ag thin film is separated from the domain due to the island growth. As a result, it can be seen that the sheet resistance is 0.274kΩ / sq.

On the other hand, as shown in FIGS. 4B and 4C, when the dopant such as Mg and Ti is contained at 3 wt.%, The growth mode of the Ag thin film progresses to LbL growth and the surface is flat.

Also, it can be confirmed that domains are connected to each other with a sheet resistance of 10? / Sq or less.

The metal layer 54 is deposited on the gallium nitride based semiconductor layer to confirm that some holes are formed from the gallium nitride based semiconductor.

FIG. 5 shows X-ray diffraction results when an Ag thin film is deposited according to an embodiment of the present invention, and shows a result of comparison according to presence or absence of a dopant.

In particular, X-ray diffraction results are shown when Ag thin film and Ag thin film doped with 3 wt.% Of Mg and Ti are deposited 100 Å on gallium-based semiconductor layer.

It can be seen that the diffraction peak near 37 ° of the 2θ (theta) position is the Ag (111) peak.

The Ag (111) surface is the lowest surface energy of the poly-crystalline Ag thin film, and it can be confirmed that it is mainly composed of the (111) surface.

However, it can be seen that the position of the Ag (111) diffraction peak is significantly different when Mg and Ti dopants are added.

In the case of Ag deposition, the stress on the formation of the Ag (111) plane was small, but when the dopant was contained, the peak position of the Ag (111) was observed at a significantly high 2Θ position. Which means that compressive stress is present in the Ag thin film.

As shown in FIG. 4, it can be seen that the Ag thin film, which is present as a polycrystalline film when depositing, forms an island-shaped domain due to the migration of atoms to the (111) surface with low surface energy.

However, when the dopant is contained, the atoms can not migrate easily due to the compressive stress inside the Ag thin film and grow LbL.

FIG. 6 is a graph showing refractive indexes and absorption coefficients of an Ag thin film according to dopants added according to an embodiment of the present invention. FIG.

When 3 wt.% Of the dopant is contained in the Ag thin film, the refractive index shown in the left side of FIG. 6 shows a value similar to that of Ag at a wavelength of 500 nm or less, while it has a refractive index of 0.3 lower than that of the Ag thin film at a wavelength of 500 nm or more .

On the other hand, it can be seen that the absorption coefficient (k) shown on the right side of FIG. 6 shows a similar value regardless of the presence or absence of the dopant in all the wavelength ranges.

FIG. 7 shows the thicknesses of the Ag metal layer and the MoO ₃ metal oxide layer having the highest transmittance at 450 nm according to the present invention, and shows a comparison result according to the presence or absence of the dopant.

Based semiconductor layer is used as the support layer 40. When Mg and Ti are added as well as when dopant is not added, an optical effect having a high transmittance of about 98% can be obtained. The transparent electrode 50 having a low surface resistance can be obtained.

As described above, in the present invention, a small amount of dopant (dopant) is used in the Ag thin film to change the growth mode of the Ag thin film.

At this time, the Ag atoms that are deposited with a high energy are moved to the most stable site due to the energy of their own after deposition or adsorption on the substrate.

Particularly, the Ag thin film deposited by the polycrystallization proceeds to the (111) plane having the lowest surface energy and its own energy when it is separated from the source acts as a driving force, ) Phenomenon occurs.

Thus, in the initial stage of the deposition, the (111) plane grows into the island growth mode.

However, when Mg or Ti atoms having a lower oxygen chemical potential than Ag are deposited together, Mg-O or Ti-O chemical bonding is formed during the deposition and the metal- Due to the volume expansion due to oxygen bonding, compressive stress is applied inside the Ag thin film.

For this reason, diffusion of Ag atoms is reduced and Ag-type thin films are grown in LbL mode.

Therefore, the domains of the Ag thin film can be connected even at a low thickness to form a metal layer having a low sheet resistance, and high-performance transparent electrodes and optical elements can be manufactured using the metal layer.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. In addition, it is a matter of course that various modifications and variations are possible without departing from the scope of the technical idea of the present invention by anyone having ordinary skill in the art.

40: support layer 50: transparent electrode
52: contact layer 54: metal layer
56, 58: metal oxide layer

Claims (14)

Forming a metal layer made of Ag and a dopant material such as Mg, Ti, Cu, In, or an alloy thereof on a supporting layer such as a semiconductor layer; And
Forming a first metal oxide layer on the metal layer; And forming a transparent electrode. The method according to claim 1,
Further comprising forming a contact layer on the support layer before forming the metal layer. 3. The method of claim 2,
Further comprising forming a second metal oxide layer on the contact layer prior to forming the metal layer. 3. The method of claim 2,
Wherein the contact layer, the metal layer, and the first metal oxide layer are formed by a thermal evaporation process, an electron beam evaporation process, or a sputter process. 3. The method of claim 2,
Wherein the contact layer includes at least one selected from the group consisting of Ni, Ti, Pt, and Cr. 3. The method of claim 2,
Wherein the thickness of the contact layer is 1 to 10 angstroms. The method according to claim 1,
Wherein the amount of the dopant added to the Ag is 0.1 to 10 wt%. 8. The method of claim 7,
Wherein the metal layer has a sheet resistance of 10 Ω / sq or less at a thickness of 100 Å or less. The method according to claim 1,
Wherein the metal layer has a thickness of 10 to 100 ANGSTROM. The method according to claim 1,
Wherein the first metal oxide layer comprises at least one selected from the group consisting of MoOx, WOx, VOx, NiOx and RuOx. 11. The method of claim 10,
Wherein the first metal oxide has an oxygen content (x) of 1 to 10. A transparent electrode formed by the method according to any one of claims 1 to 11. A light emitting diode comprising a transparent electrode formed by the method according to any one of claims 1 to 11. An optical element comprising a transparent electrode formed by the method according to any one of claims 1 to 11.

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