KR20010057124A - Organic light emitting device having double barrier quantum well structure - Google Patents

Abstract

PURPOSE: An organic luminescent element using a double barrier quantum well structure is provided to promote efficiency by accelerating injection of electrons by employing a double barrier quantum well structure. CONSTITUTION: A transparent anode(103) is formed on a substrate(101). A luminescent layer(105) is formed on the anode and emits light according to application of a voltage. The first insulation layer(110) is formed on the luminescent layer and forms an energy barrier. A metallic layer(112) is formed on the first insulation layer and forms a quantum well. The second insulation layer(114) is formed on the metallic layer and forms an energy barrier. A cathode(107) is formed on the second insulation layer. The anode is ITO(Induim tin Oxide). The insulation layer and the metallic layer are formed between the luminescent layer and the cathode to form a double barrier quantum well structure, whereby efficiency is improved and an operation voltage is decreased.

Description

ORGANIC LIGHT EMITTING DEVICE HAVING DOUBLE BARRIER QUANTUM WELL STRUCTURE}

The present invention relates to an organic light emitting device, and in particular, to form a multi-barrier quantum well structure between the light emitting layer and the cathode to improve the injection of electrons from the cathode to the light emitting layer to reduce the operating voltage and improve the efficiency of the double barrier quantum well It relates to an organic light emitting device having a structure.

Recently, since organic light emitting devices using poly (p-phenylinvinyline) (PPV), which is one of conjugated polymers, have been developed, research on organic materials such as conjugated polymers with conductivity has been actively conducted. Research on applying such organic materials to thin film transistors, sensors, lasers, photoelectric devices, and the like continues, and among them, researches on organic light emitting devices are most actively conducted.

Electroluminescent devices made of phosphor-based inorganic materials require an operating voltage of 200V or more and the manufacturing process of the device is made by vacuum deposition, which makes it difficult to enlarge the size, in particular, it is difficult to emit blue light and the manufacturing cost is high. have. However, the light emitting device made of organic material has the advantages of excellent luminous efficiency, large area, ease of process, especially blue light emission, and the development of a light emitting device that can bend. As the spotlight.

1 illustrates a conventional organic light emitting diode, and FIG. 2 is a band diagram of the organic light emitting diode. As shown in FIG. 1, the organic light emitting diode has a structure in which a light emitting material is inserted between a metal electrode having a high work function and a low metal electrode. The metal electrode having a high work function is used as an anode (3) for injecting holes and the metal electrode having a low work function is used as a cathode (7) for injecting electrons.

In order to emit the emitted light to the outside of the light emitting device, the substrate and one electrode are made of a transparent material having almost no light absorption in the light emitting wavelength region. Indium Tin Oxide (ITO) is most commonly used as the transparent electrode, and this metal is usually used as the anode 3 into which holes are injected. As the cathode 7, a metal having a low work function is generally used to facilitate the injection of electrons.

The principle of light emission of the organic light emitting device is as follows. When holes and electrons are injected into the light emitting layer 5 in the anode 3 and the cathode 7 having a high work function, excitons are generated in the light emitting layer 5, and the excitons decay. As a result, light corresponding to the energy difference between the low unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) of the light emitting layer 15 shown in FIG. 2 is generated.

At present, the research of the organic light emitting device is mainly focused on improving the efficiency (efficiency) and life of the device. The charge injection characteristic at the interface between the organic light emitting material and the electrode has the greatest influence on the quantum efficiency and operating voltage of the light emitting device and plays a significant role in the lifetime. Research is mainly focused on improving interfacial properties.

Carrier mobility in organic materials generally moves holes more easily than electrons due to ionization potential and electron affinity. That is, excitons are generated near the cathode because electrons are not easily moved within the organic material, but the quantum efficiency of the organic light emitting device is degraded because the non-light emission is large near the electrode.

Therefore, in order to improve the efficiency of the device, injection of electrons and holes into the light emitting layer is sufficiently performed, and the injected electrons and holes must be balanced. An ideal light emitting device should have the Fermi level of the electrode metal and the HOMO and LUMO levels of the light emitting material.

For the reasons described above, research for improving the efficiency of the offshore organic light emitting device is focused on the following two methods.

The first is efficiency improvement by electrode. When a metal having a small work function, such as Ca, is used as the cathode, the energy barrier between LUMO of the light emitting layer and the Fermi level of the cathode is lowered, so that sufficient electrons are injected into the light emitting layer. However, there is a problem that Ca is extremely unstable in air. In addition, since Ca not only provides electrons to the double bonds in the organic material but also easily diffuses into the organic material to dope the organic material, Ca has a problem of unstable electrical characteristics of the device by flowing a leakage current. In particular, since the metal acts as a quenching site in the organic layer, the efficiency of the single film device where recombination occurs near the metal interface is drastically reduced.

Second, the structure of the light emitting device is formed using a heterojunction using two or more organic materials having different band gaps. Since the structure of the electrons is lower than the mobility of the holes, the structure can suppress the movement of the holes to increase the local charge density, thereby facilitating the injection of electrons by the space charge field, and the ability to transport the electrons. By using this good material, electrons are introduced into the collision radius where they can recombine with the holes, thereby increasing the luminous efficiency.

The heterojunction structure can be made by forming a charge transport layer between the light emitting layer and the electrode. The charge transport layer includes an electron transport layer and a hole transport layer, and the charge transport layer functions as follows.

First, the charge transport layer efficiently transports carriers to the light emitting material, thereby increasing the probability of light emission coupling in the light emitting layer.

Second, the HOMO or LUMO level of the charge transport material is somewhat different from that of the light emitting material, thereby blocking the transport of the carrier. For example, the electron transport layer suppresses the flow of holes at the interface with the light emitting layer to increase the electric field in the electron transport layer, so that the electron injection from the cathode is improved.

Third, in the case where the hole mobility is higher than the electron mobility in the light emitting layer, luminescence recombination mainly occurs near the cathode to form singlet exciton, and near the cathode, the metal defect diffused from the metal electrode is non-existent. It acts as a source of luminescence decay, reducing the probability of luminescence recombination. When the electron transport layer is formed, the light emitting recombination occurs at the interface between the light emitting layer and the transport layer, so that there is a certain distance from the metal electrode, thereby reducing exciton.

However, the organic light emitting device in which the charge transport layer, in particular the electron transport layer, is formed has the following problems. For example, in the organic light emitting device including the electron transport layer proposed by Hosokawa et al., Since tris (8-hydroxyquinoline) aluminum (Alq) is used as the electron transport layer, the organic light emitting device is doped from a cathode composed of Mg: Ag. The electron injection is facilitated by the distriry arylene light emitting layer to obtain sufficient blue light emission (C. Hosokawa, H.Higashi, H.Nakamura, and T.Kusumoto, Appl. Phys. Lett. 67. 3853 ( 1995)). However, in the organic light emitting device having the above structure, part of the recombination region extends to Alq, so that a green region occurs on the emission spectrum. Therefore, there exists a problem that the efficiency as a blue light emitting element falls.

An object of the present invention is to provide an organic light emitting device capable of improving efficiency by introducing a double barrier quantum well structure between a light emitting layer and a cathode to promote electron injection.

In order to achieve the above object, the organic light emitting device according to the present invention comprises a substrate, an anode formed on the substrate, a light emitting layer formed on the anode to emit light upon application of voltage, and formed on the light emitting layer into the light emitting layer A double barrier quantum well structure for promoting the injection of electrons, and a cathode formed on the double barrier quantum well structure.

The double barrier quantum well structure includes a first energy barrier formed between the light emitting layer and the cathode, a second energy barrier adjacent to the first energy barrier, and a quantum well formed between the first energy barrier and the second energy barrier. Is done. The first energy barrier and the second energy barrier are each an insulating layer made of LiF, and the quantum well is a metal layer made of aluminum.

A polymer electrode and a mixed electrode or a hole transport layer may be formed between the light emitting layer and the anode to improve injection of holes into the light emitting layer, and an electron transport layer may be formed between the light emitting layer and the cathode. The polymer electrode mainly uses PANI or PEDT, and the mixed electrode uses PANI: PVK. In addition, PVK or TPD is used as the hole transport layer, and Alq or PBD is used as the electron transport layer.

1 is a view showing the structure of a conventional organic light emitting device.

Figure 2 is a band diagram of a conventional organic light emitting device.

3 is a band diagram of the organic light emitting device according to the present invention.

4 is a view showing the structure of an organic light emitting device according to the present invention.

5 is a graph showing a characteristic curve of voltage versus current of an organic light emitting diode according to the first and second embodiments of the present invention.

6 is a graph showing characteristic curves of voltage versus luminance of organic light emitting diodes according to the first and second exemplary embodiments of the present invention;

-Brief description of the symbols for the main parts of the drawing.

103: ITO 105: light emitting layer

110: first insulating layer 112: metal layer

114: second insulating layer 107: cathode

In the present invention, a double barrier quantum well structure is introduced between the light emitting layer and the cathode to improve the efficiency of the organic light emitting device. The double-barrier quantum well structure is a structure in which quantum wells exist between two energy barriers, causing a resonant tunneling effect.

The double barrier quantum well structure is illustrated in FIG. 3, and the physical action thereof is as follows. Electrons emitted from the electrode E and passing through the two energy barriers B1 and B2 pass through the second energy barrier B2 and pass through the low energy quantum well W to pass the next first energy barrier B1. Meet. At this time, since two energy barriers B1 and B2 and the quantum well W interact with each other, resonance tunneling occurs. Electrons that initially pass through the second energy barrier B2 do not pass through the first energy barrier B1 and are reflected.

Therefore, in the quantum well W, electrons passing through the second energy barrier B2 and electrons reflected from the first energy barrier B1 are present together, so that constructive or destructive interference occurs between the two electrons depending on the energy. This happens. Therefore, at the energy level where offset interference occurs, electrons rarely pass through the energy barrier, and at the level where constructive interference occurs, all electrons can pass through the energy barrier. This phenomenon is called resonant tunneling, and this phenomenon can improve the injection of electrons from the cathode.

An organic light emitting diode to which the double barrier quantum well structure is applied is illustrated in FIG. 4. As shown in the figure, the organic light emitting device of the present invention is made of a transparent metal such as ITO on the glass substrate 101 is laminated a positive electrode 103, the voltage is applied, the application of the voltage on the anode 103 The light emitting layer 105 which emits light is stacked.

The light emitting layer 105 mainly consists of an organic light emitting material, and the organic light emitting material is HP (Para-Hexaphenyl) or DPVBi (4,4'-bis (2,2-diphenylvinyl) -1,1'-iphenyl), Alternatively, BCzVBi (4,4'-bis [2- (3-N-ethylcarbazoryl) vinyl] biphenyl) may be used, but the present invention mainly uses para-hexaphenyl having a maximum wavelength of 425 nm. Of course, the light emitting material does not need to be limited. The reason for using the PHP is an example of the present invention is not limited to the organic light emitting material of the present invention. That is, all the light emitting materials used in the general organic light emitting device can be used excellently.

The first insulating layer 110 is stacked on the light emitting layer 105, and the metal layer 112 and the second insulating layer 114 are stacked thereon, respectively. The first insulating layer 110, the metal layer 112, and the second insulating layer 114 are for forming a double barrier quantum well structure in the organic light emitting diode, and the first insulating layer 110 and the second insulating layer ( 114 is made of LiF, MgF ₂ , SiO, SiO ₂ or Al ₂ O ₃ and the metal layer 112 is made of aluminum, silver, or indium. That is, the first energy barrier B1 and the second energy barrier B2 shown in FIG. 3 are formed by the first insulating layer 110 and the second insulating layer 114, and the quantum well is formed by the metal layer 112. (W) is formed.

The insulating layers 110 and 114 forming the energy barrier are stacked to have a thickness of about 5 to 35 각각, respectively. Although the operating voltage of the organic light emitting device is reduced by the formation of the double barrier quantum well structure, when the thickness of the energy barrier (that is, the thickness of the insulating layer) is too large, the luminous efficiency is lowered. Therefore, it is preferable to form an insulating layer in the thickness of about 10-20 micrometers.

The cathode 107 is formed on the second insulating layer 114. Like the metal layer 112, the cathode 107 is made of aluminum, and light is emitted from the light emitting layer 105 as a voltage is applied.

In general, an organic light emitting diode uses a metal having a small work function such as Ca, Mg, Li, etc. as a cathode to improve the efficiency of the device. However, these metals have instabilities that are easily oxidized in the air due to their strong reactivity, and diffusion into the organic material layer (ie, the light emitting layer) occurs, thereby degrading the performance of the device. In the present invention, by introducing the double-barrier quantum well structure, it is possible to use cheap and stable metals such as aluminum (Al), silver, indium, etc. as the cathode instead of the metal having a low work function as described above.

Although not shown in the drawing, a polymer electrode, a mixed electrode, or a hole transport layer may be formed between the ITO 103 and the light emitting layer 105 to improve the injection of holes into the light emitting layer 105.

The polymer electrode is formed by applying on the ITO 103 as a conductive insulating layer. In the present invention, polyaniline (PANI) or polyethylen dioxythiophene (PEDT) is used as the polymer electrode. In general, since PANI or PEDT is an insulating material, dopants such as 10-Camphor-Sulonic Acid (CSA) or polystyrenesulfonic acid (PSS) are used to impart conductivity. Injection is improved.

In addition, in the present invention, a PANI: PVK mixed polymer electrode may be used instead of the polymer electrode made of PANI or PEDT. Since the PANI: PVK polymer electrode is a mixture of a polymer electrode material and a hole transport material, the hole injection from the anode (ITO) to the light emitting layer 105 is improved by improving the interfacial properties between the ITO 103 and the light emitting layer 105. The efficiency of the organic light emitting device can be significantly improved by.

As the hole transport layer, poly (N-vinylcarbazole) (PVK) or TPD (N, N'-diphenyl-N, N'-bis (3-methylphenyl)-(1,1'-biphenyl) -4,4 ' -diamine) and Alq and PBD (2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole) are used as the electron transport layer. Injection of holes into the light emitting layer 105 may be improved by the hole transport layer, thereby improving efficiency of the organic light emitting device, and electron injection into the light emitting layer 105 may be improved by the electron transport layer. This can be improved.

Hereinafter, a method of manufacturing an organic light emitting diode according to the present invention will be described in detail with reference to Examples. The organic light emitting device manufactured in Example is for an organic light emitting device having the above-described structure, but such a structure is not limited. That is, the contents disclosed in the following examples are merely examples of the invention and do not define the scope of the invention.

Conditions exemplified in the following method, for example, concentration, mixing ratio of solution, drying temperature, drying time and the like are one example for describing the invention in detail.

Example 1

① ITO (Indium Tin Oxide) was laminated to a glass substrate laminated in a set thickness in trichloroethylene (trichloroethylene) and then ultrasonically washed, and then washed in the same way in acetone and iso-propyl alcohol (IPA). Drying was carried out with nitrogen between each of the washing procedures described above. The washed ITO is transferred into a glove box. The inside of the glove box was kept in an argon atmosphere to maintain concentrations of oxygen and water at several ppm, and all subsequent processes were performed in the glove box.

② After mixing 0.5 moles of CSA (or PSS) per mole of PANI repeating units, it was dissolved in m-cresol to form a PANI-CSA solution, and the solution was filtered and used only to dissolve uniformly. PVK was dissolved in chloroform with a solvent, and then filtered to use only the completely dissolved portion. The PANI-CSA solution and the PVK solution were mixed to form a PANI: PVK mixed solution having a concentration of about 10.0%.

The mixed PANI: PVK mixed solution was spin-coated at about 4000 rpm for about 120 seconds, and then dried for about 10 to 14 hours at a temperature of about 50 to 70 ° C. under a vacuum of about 1.0 × 10 ⁻⁵ Torr or less and then PANI: PVK A mixed electrode was formed.

③ A hole transport layer was formed on the PANI: PVK mixed electrode by depositing TPD, which is a hole material, at about 450 to 550 Pa at a rate of about 2 to 3 Pa / s under a vacuum of about 1.0 × 10 ⁻⁶ Torr or less.

(4) The light emitting layer was formed by depositing PHP as a light emitting material on the hole transport layer at a rate of about 2 to 3 mW / s at about 450 × 550 m / s under a vacuum of about 1.0 × 10 ⁻⁶ Torr or less.

(5) LiF was deposited on the light emitting layer under a vacuum of about 1.0 x 10 ^-6 Torr or less at a rate of about 0.2 kPa / s, and then aluminum was deposited about 10 to 20 kPa. Subsequently, LiF was further deposited on the aluminum layer to a thickness of about 10 to 20 microns to form a double barrier quantum well structure including a LiF layer, an aluminum layer, and a LiF layer.

(6) A cathode was formed on the double barrier quantum well structure by laminating a metal having a high work function such as aluminum and inexpensive metal by vacuum deposition or sputtering. At this time, the cathode was deposited at a rate of about 5.0 kW / s under a vacuum of about 1.0 × 10 ⁻⁶ Torr or less to form a thickness of about 500 to 1500 kW.

⑦ wire bonding was performed on the LiF: PVK composite electrode and the cathode using silver paste.

Example 2

Example 5 of Example 1 and LiF deposited on the light emitting layer in a vacuum of about 1.0 × 10 ^-6 Torr or less at a rate of about 0.2 kW / s to about 10 to 20 kW and then about 25 to 35 kW of aluminum Fabricated organic light emitting diodes with different sized quantum well structures.

Comparative example

① ITO (Indium Tin Oxide) was laminated to a glass substrate laminated in a set thickness in trichloroethylene (trichloroethylene) and then ultrasonically washed, and then washed in the same way in acetone and iso-propyl alcohol (IPA). Nitrogen was dried between each of the above washing procedures. The washed ITO is transferred into a glove box. The inside of the glove box was kept in an argon atmosphere to maintain concentrations of oxygen and water at several ppm, and all subsequent processes were performed in the glove box.

② After mixing 0.5 moles of CSA (or PSS) per mole of PANI repeating units, it was dissolved in m-cresol to form a PANI-CSA solution, and the solution was filtered and used only to dissolve uniformly. PVK was dissolved in chloroform with a solvent, and then filtered to use only the completely dissolved portion. The PANI-CSA solution and the PVK solution were mixed to form a PANI: PVK mixed solution having a concentration of about 10.0%.

The mixed PANI: PVK mixed solution was spin-coated at about 4000 rpm for about 120 seconds, and then dried for about 10 to 14 hours at a temperature of about 50 to 70 ° C. under a vacuum of about 1.0 × 10 ⁻⁵ Torr or less and then PANI: PVK A mixed electrode was formed.

③ A hole transport layer was formed on the PANI: PVK mixed electrode by depositing TPD, which is a hole material, at about 450 to 550 Pa at a rate of about 2 to 3 Pa / s under a vacuum of about 1.0 × 10 ⁻⁶ Torr or less.

(4) The light emitting layer was formed by depositing PHP as a light emitting material on the hole transport layer at a rate of about 2 to 3 mW / s at about 450 × 550 m / s under a vacuum of about 1.0 × 10 ⁻⁶ Torr or less.

⑤ LiF is deposited on the light emitting layer under a vacuum of about 1.0 × 10 ⁻⁶ Torr or less at a rate of about 0.2 to 20 kW / s to form a single barrier structure, and then a metal such as aluminum is deposited by vacuum deposition or sputtering. To form a negative electrode. At this time, the cathode was deposited at a rate of about 5.0 kW / s under a vacuum of about 1.0 × 10 ⁻⁶ Torr or less to form a thickness of about 500 to 1500 kW.

⑥ Wire bonding was performed on the PANI: PVK composite electrode and the cathode using silver paste.

The characteristics of the organic light emitting diodes manufactured by Examples 1 and 2 and Comparative Example 1 are shown in FIGS. 5 and 6.

5 is a graph showing a voltage-current characteristic curve of the fabricated organic light emitting diode, and FIG. 6 is a graph showing a characteristic curve of current-luminance. In the figure, the black circle represents the characteristic curve of the organic light emitting device having a metal layer thickness of about 30 μs and the empty circle represents the characteristic curve of the organic light emitting device having the thickness of about 15 μm of the double barrier quantum well structure. Squares represent the characteristic curves of the organic light-emitting device having a single barrier.

First, as shown in the voltage-current characteristic curve of FIG. 5, as the voltage is applied to the anode (ITO) and the cathode of the organic light emitting diode, the current of each organic light emitting diode increases exponentially. The voltage-current characteristic curve represents the operating voltage of the organic light emitting diode, which is a very important factor that determines the performance of the organic light emitting diode.

As shown in the figure, the operating voltage (voltage at which the current starts to increase exponentially) of the single barrier organic light emitting diode is about 10V, whereas the organic light emitting diode having the double barrier quantum well structure operates about 5.5V. Has a voltage. Therefore, it can be seen that the operating voltage of the organic light emitting device having the double barrier quantum well structure is significantly lower than the operating voltage of the organic light emitting device having the single barrier structure or the conventional organic light emitting device having no energy barrier.

In addition, as shown in the voltage-luminance characteristic curve of FIG. 6, it can be seen that the luminance of the organic light emitting device having the double barrier quantum well structure is significantly improved compared to the organic light emitting device having the single barrier structure. In addition, the efficiency of the organic light emitting diode having a thickness of about 15 GPa is further improved compared to the organic light emitting diode having a thickness of about 30 GPa.

As described above, by forming a double barrier quantum well structure between the light emitting layer and the cathode, it is possible to lower the operating voltage of the organic light emitting device and to improve efficiency.

In the above embodiment, an organic light emitting device having a specific structure is manufactured by a specific method for convenience of description, but the organic light emitting device of the present invention is not limited to the above embodiment. For example, it is also possible to form three or more insulating layers and two or more metal layers between the light emitting layer and the cathode to form a quantum well structure of three or more barriers instead of a double barrier.

Therefore, the scope of the present invention should be determined not by the above-described embodiments, but by the appended claims.

As described above, the organic light emitting device according to the present invention forms an insulating layer and a metal layer forming a double-barrier quantum well structure between the light emitting layer and the cathode, whereby an organic light emitting device having a greatly improved efficiency and a low operating voltage can be obtained. .

Claims (25)

Board; A transparent anode formed on the substrate; An emission layer formed on the anode to emit light as a voltage is applied; A first insulating layer formed on the light emitting layer to form an energy barrier; A metal layer formed on the first insulating layer to form a quantum well; A second insulating layer formed on the metal layer to form an energy barrier; And An organic light emitting device consisting of a cathode formed on the second insulating layer. The organic light emitting device of claim 1, wherein the anode is indium tin oxide (ITO). According to claim 1, wherein the light emitting layer is para-hexaphenyl (para-hexaphenyl), DPVBi (4,4'-bis (2,2-diphenylvinyl) -1,1'-iphenyl), BCzVBi (4,4'-bis An organic light emitting device, comprising: a material selected from the group consisting of [2- (3-N-ethylcarbazoryl) vinyl] biphenyl). The organic light emitting diode of claim 1, wherein the first insulating layer is formed of a material selected from the group consisting of LiF, MgF ₂ , SiO, SiO _2, and Al ₂ O ₃ . The organic light emitting device according to claim 5, wherein the LiF has a thickness of 10 to 20 GPa. The organic light emitting device of claim 1, wherein the metal layer is made of a material selected from the group consisting of aluminum, silver, and indium. The organic light emitting device of claim 6, wherein the metal layer has a thickness of about 10 to about 20 microns. The organic light emitting device according to claim 6, wherein the metal layer has a thickness of 25 to 35 GPa. The organic light emitting device of claim 1, wherein the second insulating layer is formed of a material selected from the group consisting of LiF, MgF ₂ , SiO, SiO _2, and Al ₂ O ₃ . 10. The organic light emitting device of claim 9, wherein the second insulating layer has a thickness of about 10 to about 20 microns. The organic light emitting device of claim 1, wherein the cathode is made of a material selected from the group consisting of aluminum, silver, and indium. 12. The organic light emitting device of claim 11, wherein the cathode has a thickness of 500 to 1500 mW. The organic light emitting device of claim 1, further comprising a polymer electrode formed between the anode and the light emitting layer. The organic light emitting diode of claim 13, wherein the polymer electrode is made of a material selected from the group consisting of polyaniline (PANI) and polyethylen dioxythiophene (PEDT). The organic light emitting diode of claim 13, wherein the polymer electrode is a PANI: PVK (poly (N-vinylcarbazole)) mixed electrode. The organic light emitting device of claim 1, further comprising a hole transport layer formed between the anode and the light emitting layer. The method of claim 16, wherein the hole transport layer is poly (N-vinylcarbazole) (PVK) and TPD (N, N'-diphenyl-N, N'-bis (3-methylphenyl)-(1,1'-biphenyl) ) -4,4'-diamine) organic light emitting device, characterized in that consisting of a material selected from the group consisting of. The organic light emitting device of claim 1, further comprising an electron transport layer formed between the light emitting layer and the first insulating layer. The electron transport layer of claim 18, wherein the electron transport layer comprises tris (8-hydroxyquinoline) aluminum (Alq) and PBD (2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole. An organic light emitting device, characterized in that consisting of a material selected from the group consisting of. Board; An anode formed on the substrate; An emission layer formed on the anode and emitting light when voltage is applied; A multi-barrier quantum well structure formed on the light emitting layer to facilitate injection of electrons into the light emitting layer; And An organic light emitting device comprising a cathode formed on the multi-barrier quantum well structure. The method of claim 20, wherein the multi-barrier well structure, At least one first energy barrier formed over the light emitting layer; At least one second energy barrier adjacent the first energy barrier; And And at least one quantum well formed between the first energy barrier and the second energy barrier. The organic light emitting device of claim 21, wherein the first energy barrier is made of a material selected from the group consisting of LiF, MgF ₂ , SiO, SiO _2, and Al ₂ O ₃ . The organic light emitting device of claim 21, wherein the second energy barrier is made of a material selected from the group consisting of LiF, MgF ₂ , SiO, SiO _2, and Al ₂ O ₃ . The organic light emitting device of claim 21, wherein the quantum well is made of a material selected from the group consisting of aluminum, silver, and indium. 22. The organic light emitting device of claim 21, wherein the organic light emitting diode is made of a material selected from the group consisting of aluminum, silver, and indium.