KR100990451B1 - High Efficiency Phosphorescent Organic Light Emitting Diodes using Sandwich-Mixed Double Emission Hosts and their Fabrication Methods - Google Patents

Abstract

The present invention relates to a highly efficient phosphorescent organic light emitting diode using a sandwich-mixed dual light emitting host and a method of manufacturing the same. The phosphorescent organic light emitting device includes a first electrode formed on a substrate, a second electrode facing the first electrode, and a light emitting layer positioned between the first electrode and the second electrode, wherein the light emitting layer is a hole transporting light emitting host. And a dual light emitting host having a sandwich mixture structure consisting of a hole transfer light emitting host and an electron transfer light emitting host.

According to the present invention, problems such as low efficiency and short lifespan of existing organic light emitting devices can be solved, and there is an effect of providing a phosphorescent organic light emitting device having a large improvement in light emitting efficiency by a simple process.

PhOLED, Phosphorescent Organic Light Emitting Diode, Luminous Efficiency, Sandwich Mixing, Dual Luminous Host

Description

High Efficiency Phosphorescent Organic Light Emitting Diodes Using Sandwich-Mixed Double Emission Hosts and Their Fabrication Methods

The present invention relates to a highly efficient phosphorescent organic light emitting diode using a sandwich-mixed dual light emitting host and a method of manufacturing the same. Phosphorescence that can greatly improve the luminous efficiency of the phosphorescent device by a simple method, including a light emitting layer structure composed of a host and an electron transfer light emitting host (hereinafter, referred to as a sandwich-mixed double emission hosts structure). An organic light emitting diode and a method of manufacturing the same.

Phosphorescent Organic Light Emitting Diodes (PHOLED) have basically a structure in which organic material is inserted between a substrate (glass, plastic, etc.), upper and lower electrodes (anode and cathode), and two electrodes. Organic materials are usually multi-layered and consist of a hole transport layer (HTL, hole transport layer) / light emitting layer (hereinafter EML, emissive layer) / hole blocking layer (HBL, hole blocking layer) / electron transport layer (ETL, electron transport layer) do. That is, PhOLEDs are formed of a first electrode (anode electrode) 11 / hole injection layer (HIL) 12 / hole transport layer (HTL) 13 / light emitting layer (EML) 14 / as shown in FIG. A hole blocking layer (HBL) 15 / electron transport layer (ETL) 16 / second electrode (cathode electrode) 17 is provided.

In this case, the organic material of the EML 14 generally uses a host-dopant structure rather than a single material. In such a structure, carriers are not injected directly from the electrode to the light emitting layer, but are gradually transmitted through the carrier transport layer, thereby lowering the driving voltage. In the multilayer structure, when electrons and holes injected into the light emitting layer move to the neighboring electrode, the movement is limited by the carrier transport layer of opposite polarity near the edge of the light emitting layer, so that excitons are bound to the light emitting layer and the light emission efficiency is increased. In addition, PhOLEDs can shine from both singlet and triplet excitons, and the internal quantum efficiency is theoretically 100%, but in real devices, carrier injection losses, non-luminescent excitons are formed, triple-triplet extinction, etc. As a result, the luminous efficiency is greatly reduced. In addition, the triplet excitons formed in the light emitting layer of the phosphorescent device have a relatively long lifespan and may diffuse through the EML region to other regions. Diffusion of triplet excitons causes energy transfer or non-luminescent extinction outside the EML region, resulting in poor luminous efficiency and color purity. Therefore, in order to fabricate a high-efficiency phosphorescent device, the composition of the light emitting layer (material, thickness, doping concentration, etc.) must be well designed, and an exciton protection layer must be installed to prevent diffusion loss of triplet excitons. .

Accordingly, a method of using a single host in the light emitting layer of PhOLEDs is known as a method for preventing diffusion loss of triplet excitons. According to the method, excitons are generated at the edges of the EML region, as the host usually selectively transports carriers of either type, either electrons or holes. However, when the exciton generation is generated at the edge of the EML, the luminous efficiency and color purity of the device are reduced.

Accordingly, recently, PhOLEDs having a light emitting layer using a mixture of a host having excellent electron transfer and a hole having good hole transfer or using a stacked structure thereof have been studied. 2 shows a light emitting layer having a simple mixed structure, and FIG. 3 shows a light emitting layer having a double stacked structure. In FIG. 2, the light emitting host layer 20 is an organic layer made by simply mixing a hole transporting light emitting host and an electron transporting light emitting host. In FIG. It is a structure made by stacking hosts sequentially.

In the simple mixed structure and the stacked structure using the dual host according to FIGS. 2 and 3, the exciton is mainly formed in the entire region of the light emitting layer and in the central region having the heterogeneous boundary of the light emitting layer, respectively, and thus, the injection loss of the carrier and the diffusion loss of the triplet exciton are different. There is an advantage that can be prevented to some extent. However, in the simple mixed structure, it is difficult to completely prevent the diffusion loss of triplet excitons occurring at the edge of the light emitting layer, and in the stacked structure, the exciton formation is limited near the heterojunction of the light emitting layer. That is, as shown in FIG. 4, excitons in the mixed light emitting layer may be concentrated at the edge 41 of the light emitting layer according to the hole and electron transfer characteristics, and in this case, insufficient formation of excitons in the light emitting layer and diffusion into neighboring regions ( 42) may cause exciton loss. In addition, in the dual stack structure of FIG. 5, excitons are mainly generated near the interface 50 between the hole-transmitting light emitting host and the electron-transmitting host, so that an exciton formation region is very limited in the vicinity of the junction. Exciton formation in the phosphorescent device is limited in the vicinity of the junction, so that the density of triplet excitons increases, resulting in a decrease in luminous efficiency due to triplet-triple extinction. 4 is an energy diagram of HTL / EML / ETL of a simple mixed structure, and FIG. 5 is an energy diagram of HTL / EML / ETL of a double stacked structure.

As described above, the conventional phosphorescent device has a problem in that it is difficult to completely prevent the carrier injection loss and the diffusion loss of triplet excitons occurring at the edge of the light emitting layer, thereby reducing the luminous efficiency of the device.

Therefore, in order to improve the above problems, the present invention provides a phosphorescent organic light emitting device having a sandwich mixed dual light emitting host structure consisting of a hole transporting light emitting host / mixed light emitting host / electron transporting light emitting host having excellent electroluminescent properties and a method of manufacturing the same. It is to provide.

In order to achieve the above object, the present invention is a first electrode formed on a substrate,

A second electrode facing the first electrode, and

A light emitting layer positioned between the first electrode and the second electrode,

The light emitting layer provides a phosphorescent organic light emitting diode, characterized in that it comprises a dual light emitting host having a sandwich mixture structure consisting of a hole transporting light emitting host, a hole transporting light emitting host and an electron transporting light emitting host.

In addition, the present invention comprises the steps of forming a first electrode on the substrate;

Forming a light emitting layer on the first electrode; And

Forming a second electrode on the light emitting layer

Including,

The forming of the light emitting layer may include sequentially stacking a hole transporting light emitting host layer, a hole transporting light emitting host layer, and an electron transporting light emitting host layer on a first electrode.

It provides a method for producing a phosphorescent organic light emitting diode comprising a.

Hereinafter, the present invention will be described in more detail.

In the present invention, in order to develop a new light emitting structure that can solve the problems of the low efficiency, short life, etc. of the existing PhOLEDs, we originally proposed a sandwich-mixed double emission hosts structure as a light emitting layer. As a result of comparing the device fabricated with this new structure with the existing structures, it was confirmed that the PhOLEDs having the above structure exhibited significantly improved luminous efficiency and exhibited a high lifespan. That is, the maximum luminous efficiency of the device including the sandwich-mixed dual luminous host of the present invention as a light emitting layer is evaluated as one of the highest values among the efficiency of PhOLED reported so far. In addition, the sandwich mixed dual light emitting host technology of the present invention improves the luminous efficiency of phosphorescent devices without introducing a new material or complicated process than PhOLEDs having a conventional single host structure, a simple mixed light emitting host structure, and a double stacked host structure. It can be greatly improved.

Such phosphorescent organic light emitting diodes (PhOLEDs) according to the present invention will be described in more detail with reference to the accompanying drawings.

The phosphorescent organic light emitting diode of the present invention basically includes a first electrode formed on a substrate, a second electrode facing the first electrode, and a light emitting layer positioned between the first electrode and the second electrode. In the present invention, the first electrode means an anode, and the second electrode means a cathode. The phosphorescent organic light emitting diode may further include at least one of a hole transport layer positioned between the first electrode and the light emitting layer, and an electron transport layer positioned between the second electrode and the light emitting layer. In addition, if necessary, the structure may further include a hole blocking layer positioned between the electron transport layer and the light emitting layer, and a hole injection layer positioned between the hole transport layer and the first electrode.

At this time, the present invention is a structure of the light emitting layer is not a simple mixed structure or a stacked structure of a hole transporting light emitting host and an electron transporting light emitting host as in the prior art, but a hole transporting light emitting host, a hole transporting light emitting host and It characterized in that it comprises a dual light emitting host having a sandwich mixture structure consisting of an electron transfer light emitting host.

Figure 6 shows a preferred embodiment of the light emitting layer structure portion of the present invention. As shown in FIG. 6, the light emitting layer EML of the present invention is positioned between the hole transport layer HTL and the electron transport layer ETL, wherein the light emitting layer is a hole transporting light emitting host H ₁ 61 and an electron transporting light emission. A mixture (H ₁ + H ₂ ) 62 of the two hosts 61 and 63 is positioned between the hosts H ₂ 63 to form a sandwich structure based on the mixture.

Unlike the conventional light emitting layer having a sandwich-mixed structure, diffusion loss of triplet excitons can be reduced. That is, FIG. 7 shows the energy diagram of the HTL / EML / ETL of the sandwich mixed structure of the present invention. As shown in FIG. 7, holes and electrons are transported through the respective selective transport light emitting layers 71 and 73. Since the combined light emitting layer 72 has a sufficient thickness, the carrier injection efficiency can be improved as compared with the conventional phosphorescent device, and the loss of the light emitting layer excitons due to exciton formation or diffusion in an undesired region can be reduced.

On the other hand, the mixing ratio of the hole-transmissive light emitting host and the electron-transmissive light emitting host to the mixed light emitting host is preferably mixed in a weight ratio of 3: 1 to 1: 3. At this time, if the range of the mixed weight ratio of the hole-transmitting light emitting host and the electron-transmitting light emitting host is out of the range, there is a problem that the function of the mixed layer may be lost.

In the present invention, the hole transfer light emitting host, the mixed light emitting host, and the electron transfer light emitting host may each include a phosphorescent dopant having a uniform concentration. In addition, according to the present invention, the hole-transmitting light emitting host, the mixed light emitting host, and the electron transporting light emitting host may each include a phosphorescent dopant having a non-uniform concentration.

In addition, the hole-transmitting light emitting host, the mixed light-emitting host and the electron-transmitting light-emitting host are each fluorescent material, and the dopant may be a phosphorescent material. In addition, the hole transporting light emitting host, the mixed light emitting host, and the electron transporting light emitting host and the dopant may all be phosphorescent materials.

The hole-transmitting light emitting host can be used as long as it is a light-emitting material excellent in hole transporting properties, the type is not particularly limited. Preferably, for example, at least one selected from the group consisting of an organic light emitting low molecular material, an organic light emitting polymer, and an organic light emitting oligomer may be used. More specifically, the hole-transmitting light emitting host is TCTA [4,4 ', 4' '-tris (N-carbazolyl) -triphenylamine], CBP [4,4'-bis (carba zol-9-yl) biphenyl], NPB [N, N'-bis (1-naphthyl) -N, N'-diphenyl-1,1'-biphenyl-4,4'-diamine] and PPP [poly (para-phenylene)], PPV At least one selected from the group consisting of [poly (para-phenylene vinylene)] can be used.

The electron transporting light emitting host may be used as long as the light emitting material having excellent electron transporting property, and the kind thereof is not particularly limited. For example, at least one selected from the group consisting of an organic light emitting low molecular material, an organic light emitting polymer, and an organic light emitting oligomer may be used. More specifically, the electron transfer light emitting host is TAZ [3-phenyl-4- (1-naphthyl) -5-phenyl-1,2,4-triazole], TPBI [1,3,5-tris (N -phenyl benzimidazole-2-yl) benzene], Balq [bis (8-bydroxyquinaldine) aluminum biphenoxide], PH1 (proprietary material coded by Merck), Bphen [4,7-diphenyl-1,10-phenanthroline], Bebq2 [bis At least one selected from the group consisting of (10-hydroxybenzo [h] quinolinato) beryllium], Alq ₃ [tris (8-hydroxyquinoline) aluminum], PPP and PPV can be used.

The dopant used in the present invention is preferably any one selected from the group consisting of an organic light emitting low molecular material, an organic light emitting polymer and an organic light emitting oligomer. More specifically, the dopant may be Ir (ppy) ₃ , Ir (tpy) ₃ , Ir (thpy) ₃ , Ir (piq) ₃ , Ir (fliq) ₃ , Ir (tiq) ₃ , Ir (flpy) ₃ Iridium compounds such as, Ir (btpy) ₃ , (pq) ₂ Ir (acac), (btp) ₂ Ir (acac), (F ₂ ppy) ₂ Ir (pic), FIr (pic) and PtOEP [2,3 , 7,8,12,13,17,18-octaethyl-21H, 23H-porphineplatinum (∥)] may be included.

In addition, in the formation of the emission layer EML, the total host thickness and the concentration of the phosphorescent dopant may be kept constant. In this case, when the total thickness of the light emitting layer is too thick, the current and the brightness is low, and when the thickness is too thin, the region for forming excitons is insufficient, so that the thickness of the light emitting layer is preferably 10 nm to 100 nm in consideration of appropriate current and brightness. In addition, the concentration of the dopant may be 1 to 20% with respect to the host.

In addition, the phosphorescent organic light emitting diode of the present invention, at least one selected from the group consisting of a green phosphorescent organic light emitting diode, a red phosphorescent organic light emitting diode, a blue phosphorescent organic light emitting diode, a yellow phosphorescent organic light emitting diode, and a white phosphorescent organic light emitting diode. It may include.

The preferred structure of the phosphorescent organic light emitting diode of the present invention as described above is the first electrode (anode electrode) 81 / hole injection layer (HIL) 82 / hole transport layer (HTL) 83 / light emitting layer shown in FIG. (EML) 84 / hole blocking layer (HBL) 85 / electron transport layer (ETL) 86 / second electrode (cathode electrode) 87 may be included.

In this case, holes are injected into the hole injection layer 82 on the first electrode 81 at the level of the highest occupied molecular orbital (HOMO). The hole injection layer is responsible for the function of the intermediate layer for efficiently injecting holes from the anode to the hole transport layer 83. In addition, holes injected into the hole transport layer 83 are transferred to the neighboring light emitting layer 84, and has a blocking function against the flow of electrons. Also, electrons to be combined with the holes are supplied from the second electrode (ie, cathode electrode) 87. Electrons starting from the cathode 87 are injected into the low unoccupied molecular orbital (LUMO) level of the electron transport layer 86, and are transferred to the light emitting layer 84 via the hole blocking layer 85. In most organic materials, a hole blocking layer 85 is provided between the light emitting layer 84 and the electron transport layer 86 to trap the holes in the light emitting layer because the mobility of the holes is faster than the electron mobility. Holes and electrons combine in the emission layer 84 to form excitons, and emit inherent light according to the properties and energy transfer of the excitons formed.

Meanwhile, in the present invention, the anode electrode 81, which is the first electrode, is preferably made of a transparent conductive material used in the manufacture of a general organic light emitting device. For example, the anode may be ITO, IZO or the like.

The cathode 87, which is the second electrode, is made of an opaque and highly conductive metal and reflects incident light. In addition, the cathode is an electrode into which electrons are injected and is made of a conductive material having a low work function and does not affect organic materials. For example, the cathode may be selected from aluminum (Al), calcium (Ca), and barium (Ba). Can be formed.

In addition, the material usable in the hole injection layer is 2-TNATA [4,4 ', 4 "-tris (2-naphthylphenyl-phenylamino) -triphenylamine], NPD [N, N'-di (1-naphthyl) -N , N'-diphenylbenzidine)], TPD [N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-biphenyl-4,4'-diamine], DNTPD [N, N ' -diphenyl-N, N'-bis- [4- (phenyl-m-tolyl-amino) -phenyl] -biphenyl-4,4'-diamine], etc. However, the present invention is not necessarily limited thereto.

Materials usable for the hole transport layer include NPB, TCTA, CBP and the like. However, the present invention is not necessarily limited thereto.

Materials usable for the electron transport layer include SFC137 (proprietary material coded by SFC Co.), Alq ₃ , Balq, Bphen and the like. However, the present invention is not necessarily limited thereto.

In addition, the present invention is to properly control the movement speed of the holes and electrons, and to block the passage through the light emitting layer, it can optionally form a hole blocking layer and / or electron blocking layer. As a material usable for the double hole blocking layer, BCP [2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline], Bphen, TAZ, TPBI, Balq, etc. may be used. In addition, TCTA, CBP, or the like may be used as the electron blocking layer.

On the other hand, the method of manufacturing a phosphorescent organic light emitting diode having a sandwich-mixed dual light emitting host according to the present invention is not particularly limited except for the method of forming the light emitting layer can be made by a conventional method. Preferably, one embodiment of the method of manufacturing the phosphorescent organic light emitting diode of the present invention may be performed according to the process flow diagram shown in FIG.

First, it is preferable to form the 1st electrode 81 on a glass substrate, and to plasma-process the surface of a 1st electrode suitably. Since the plasma process lowers the hole injection barrier from the first electrode (anode), contributes to surface decontamination and improving adhesion between the first electrode and the organic film, prior plasma treatment must be performed before organic material deposition.

In addition, in the high vacuum state after the plasma treatment, the organic thin film and the metal are deposited in an in-situ method, and the hole injection layer 82 and the hole transport layer 83 are sequentially deposited on the first electrode 81. It is preferable to form an organic substance.

Next, in order to deposit the light emitting layer 84, a hole transporting light emitting host is deposited together with a dopant on the hole transport layer 83, and then a hole transporting light emitting host and an electron transporting light emitting host are mixed at an appropriate ratio. After the deposition, the electron-transmitting light emitting host is sequentially deposited with the dopant. In this case, the light emitting layer is preferably formed by any one method selected from the group consisting of vacuum deposition, spin coating and inkjet printing.

Thereafter, the hole blocking layer 85 and the electron transporting layer 86 are sequentially deposited on the electron transfer light emitting host, and finally, a second electrode is formed to complete a device manufacturing process.

In the phosphorescent organic light emitting diode according to the present invention as described above, when a predetermined voltage is applied to the first electrode and the second electrode, holes injected into the first electrode and electrons injected from the second electrode are recombined at the center of the emission layer to generate energy. Emission causes light emission to occur. In this case, it is preferable to apply a voltage higher than the potential of the first electrode.

Phosphorescent organic light emitting diodes comprising a sandwich mixed dual light emitting host structure according to the present invention as a light emitting layer are compared with a conventional simple mixed light emitting host structure or a double layered host structure, and simply form organic materials without adding new materials or introducing complicated processes. Only by adjusting the deposition programming can the device be fabricated. In addition, the device of the present invention has an effect that the electroluminescence characteristics of various flat panel display devices can be greatly improved by sufficiently securing an exciton generating region near the center of the light emitting layer.

Hereinafter, preferred embodiments of the present invention will be described. However, the following examples are only illustrated to aid the understanding of the present invention, but the content of the present invention is not limited by the following examples.

Example 1

In the fabrication of the device, the basic structure was designed as ITO / 2-TNATA (500Å) / NPB (300Å) / EML / BCP (50Å) / SFC-137 (500Å) / LiF (10Å) / Al.

The EML layer has a sandwiched dual host structure of a hole transporting light emitting host / hole transporting light emitting host / electron transporting light emitting host, and the host layer is formed of TCTA (80 TC) / TCTA _1/3 TAZ _2/3 ( 90 GHz) / TAZ (130 GHz) to produce a green phosphorescent organic light emitting diode having a structure shown in FIG. 8. That is, the total host thickness of the emission layer (EML, Emissive Layer) is 300 Å. Ir (ppy) ₃ doping of the light emitting layer in all the samples by controlling the deposition rate by co-evaporation (co-evaporation), the doping concentration was uniformly maintained at 10%. At this time, TCTA [4,4,4 "-tris (2-naphthylphenyl-phenylamino) -triphenylamine] was used as a hole transporting light emitting host, and TAZ [3-phenyl-4- (1'-naphthyl) -5-phenyl -1,2,4-triazole] was used as the electron transport light emitting host, and Ir (ppy) ₃ was used as the phosphorescent dopant.

In addition, in the device structure of FIG. 8, indium tin oxide (IT0) 81 and LiF / Al 87 were used as the first electrode (anode electrode) and the second electrode (cathode electrode), respectively. In addition, 2-TNATA 83 was used as a hole injection layer and a hole transport layer, and BCP 85 and SFC137 (86) were used as hole blocking layers and electron transport layers, respectively.

At this time, the method of manufacturing a phosphorescent organic light emitting diode having a sandwich mixed dual light emitting host according to the present invention was performed according to the process flow diagram shown in FIG.

First, the ITO electrode 81 was formed on the glass substrate, and the surface of the ITO electrode was appropriately plasma-processed. After plasma treatment, the organic thin film and the metal were deposited in-situ at high vacuum. That is, the organic material was formed by depositing 2-TNATA (82) 500 Å with a hole injection layer and NPB (83) 300 Å with a hole transport layer on the ITO electrode.

Next, in order to deposit the light emitting layer, TCTA 93 was deposited on the hole transport layer NPB 84 at an 80% Ir (ppy) ₃ concentration of 80%, and then, TCTA and TAZ were mixed at a ratio of 1: 2 (94). ) to 90Å it was deposited to a 10% Ir (ppy) ₃ of concentration, and sequentially deposited in a thickness of 130Å since TAZ (95) in 10% Ir (ppy) ₃ concentrations.

Subsequently, 50 nm of BCP 85 was deposited on the TAZ 95 as a hole blocking layer, and 500 nm of SFC-137 (86) was deposited as an electron transport layer, and then a cathode was formed using LiF / Al. The manufacturing process is complete.

Comparative Example 1

A phosphorescent organic light emitting diode was manufactured in the same manner as in Example 1, except that the light emitting layer was formed of a simple mixed structure as shown in FIG. 2. In this case, as shown in FIG. 9, in the simple mixed structure, the host layer 90 was formed of a TCTA _1/3 TAZ _2/3 (300 mm ₃ ) material in which TCTA: TAZ was mixed 1: 2. Ir (ppy) ₃ doping of the light emitting layer in all the samples by controlling the deposition rate by co-evaporation (co-evaporation), the doping concentration was uniformly maintained at 10%.

Comparative Example 2

A phosphorescent organic light emitting diode was manufactured in the same manner as in Example 1, except that the light emitting layer was formed in a stacked structure as illustrated in FIG. 3. In this case, as shown in FIG. 9, the host layers 91 and 92 have a configuration of TCTA (100 μs) 91 / TAZ (200 μs) 92 in the stacked structure. Ir (ppy) ₃ doping of the light emitting layer in all the samples by controlling the deposition rate by co-evaporation (co-evaporation), the doping concentration was uniformly maintained at 10%.

Experimental Example

The electroluminescent properties of the phosphorescent organic light emitting diodes of Example 1 and Comparative Example 1-2 were compared and analyzed.

As a result, the current density and luminance of the device having the sandwich-mixed dual light emitting host of Example 1 showed 95 A / cm ² and 25000 cd / m ² at an applied voltage of 10V, respectively. As shown in FIG. 11, the maximum current luminous efficiency 111 of the device having the sandwich mixed dual light emitting host of Example 1 was 52 cd / A at a luminance of 400 cd / m ² . For reference, FIG. 11 is a diagram comparing current efficiency-luminance characteristics of the devices.

In addition, when comparing the luminous efficiency of the samples produced under a luminance of 15000 cd / m ² , the sandwich mixed device [34 cd / A 112] of Example 1 is a simple mixed light emitting host device of Comparative Example 1 [ 20 cd / A (113)] showed a light emission efficiency improvement of about 1.7 times, and compared to the double layered host device (27 cd / A (114) of Comparative Example 2), the light emission efficiency improved by about 1.3 times.

On the other hand, the electroluminescence spectrum of the device having a sandwich-mixed dual light emitting host of Example 1 at 10V applied voltage is shown in FIG.

Referring to the results of FIG. 12, the emission peaks in the electroluminescence spectrum of the device having the sandwich mixed dual light emitting host of Example 1 were about 65 nm full width at half maximum (FWHM) 121 and 513 nm center wavelength 122. Typical Ir (ppy) ₃ -triple green luminescent properties are shown.

As a result, the high current efficiency and excellent color purity characteristics of the phosphorescent device having a sandwich mixed dual light emitting host according to the present invention are obtained through the structural improvement of the light emitting layer, and the current efficiency of 52 cd / A is obtained using a pin-structure device ( NOVALED) can be evaluated as one of the highest values in PhOLEDs reported so far.

In addition, the sandwich mixed dual light emitting host of the present invention has a light emission efficiency of a phosphorescent organic light emitting device without adding a new material or a complicated process than PhOLEDs having a conventional single host structure, a simple mixed light emitting host structure, and a double stacked host structure. It can be confirmed that can be greatly improved.

In addition, in the above embodiment, a light emitting layer was formed by a vacuum deposition method using a low molecular host and a dopant to manufacture a green phosphorescent organic light emitting diode. However, the technology for manufacturing a highly efficient PhOLED device having a sandwich-mixed dual light emitting host of the present invention is used as a light emitting layer material as a polymer material or an oligomeric material, and a solution-based technology to form an organic thin film to change the color of the emitted light. The range of applications can be extended from red to blue devices.

Accordingly, while the foregoing has described preferred embodiments of the present invention, the present invention is not limited thereto, and a person of ordinary skill in the art will appreciate from the spirit and scope of the present invention described in the above-described scope and claims. It will be appreciated that various changes and modifications can be made in the present invention without departing from the scope thereof.

1 is a basic structure of a phosphorescent organic transport diode (PhOLED).

2 is a conventional light emitting layer structure in which a dual host is simply mixed.

3 is a conventional light emitting layer structure in which dual hosts are sequentially stacked;

4 is an explanatory diagram of generation of an energy band structure and an exciton of a light emitting layer structure having a conventional simple mixed double host of FIG. 2;

5 is an explanatory diagram of generation of an energy band structure and an exciton of a light emitting layer structure having a conventional sequential stacked dual host of FIG. 3;

Figure 6 is a light emitting layer structure having a sandwich mixed dual light emitting host proposed in the present invention.

Figure 7 is an explanatory view of the energy band structure and excitons of the light emitting layer structure having a sandwich mixture dual light emitting host proposed in the present invention.

8 is an overall cross-sectional view of a green phosphor using a sandwich mixed dual light emitting host structure according to an embodiment of the present invention.

Figure 9 is a host separation diagram of the light emitting layer of the prior art and the present invention when fabricating the light emitting layer host sample.

10 is a process flow diagram illustrating a method for manufacturing a highly efficient green phosphorescent organic light emitting device according to the present invention.

11 is a comparison diagram of current efficiency-luminance characteristics of a phosphorescent organic light emitting diode having a light emitting layer and a conventional light emitting layer according to the present invention.

12 is an electroluminescence spectrum at 10V applied voltage for a phosphorescent organic light emitting diode having a sandwich mixed dual light emitting host according to the present invention.

* Description of the symbols for the main parts of the drawings *

11: first electrode (anode electrode)

12: hole injection layer

13: hole transport layer

14: light emitting layer

15: hole blocking layer

16: electron transport layer

17: second electrode (cathode electrode)

20: A light emitting layer in which a hole transporting light emitting host (H ₁ ) and an electron transporting light emitting host (H ₂ ) are simply mixed in an H ₁ + H ₂ structure.

31: light emitting layer having a hole-transmissive light emitting host (H ₁ ) in a double layer structure

32: light emitting layer having an electron transport light emitting host (H ₂ ) in a double layer structure

41: neighboring region where excitons formed at the edge of the light emitting layer diffuse

42: diffusion movement of exciton formed at the edge of the light emitting layer

50: boundary region between hole-transfer light emitting host and electron-transfer light emitting host where excitons are formed in double layer structure

61: light emitting layer having a hole transporting light emitting host (H ₁ ) in a sandwich mixed dual light emitting host structure

62: light emitting layer in which hole transporting light emitting host (H ₁ ) and electron transporting light emitting host (H ₂ ) are mixed in sandwich mixed dual light emitting host structure

63: light emitting layer having an electron transport light emitting host (H ₂ ) in a sandwich mixed dual light emitting host structure

71: hole transfer light emitting host (H ₁ ) in sandwich mixed dual light emitting host structure

72: electron transfer light emitting host (H ₂ ) in sandwich mixed dual light emitting host structure

73: Exciton formation in the light emitting layer in which the hole transporting light emitting host (H ₁ ) and the electron transporting light emitting host (H ₂ ) are mixed in the sandwich-mixed dual light emitting host structure

81: ITO anode layer

82: 500-mm thick 2-TNATA hole injection layer

83: 300 nm thick NPB hole transport layer

84: Light emitting layer doped with 10% Ir (ppy) ₃ in a host having a sandwich mixture structure of TCTA (80 microseconds) / TCTA1 / 3TAZ2 / 3 (90 microseconds) / TAZ (130 microseconds)

85: 50Å thick BCP hole blocking layer

86: SFC-137 electron transport layer 500Å thick

87: 10Å / 1200Å thick LiF / Al cathode layer

90: 300 microns thick TCTA _1/3 TAZ _2/3 host layer in a simple mixed structure

91: 100 microns thick TCTA host layer in a double layer structure

92: 200 micron thick TAZ host layer in a double layer structure

93: 80 Å thick TCTA host layer in sandwich mixed structure

94: 90 Å thick TCTA _1/3 TAZ _2/3 host layer in sandwich mixed structure

95: 130 Å thick TAZ host layer in sandwich mixed structure

111: Maximum current luminous efficiency (52 cd / A at a luminance of 400 cd / m 2) of the sandwich mixed device of Example 1

112: Current luminous efficiency (34 cd / A) of the sandwich mixed device of Example 1 under a luminance of 15000 cd / m 2

113: Current luminous efficiency (20 cd / A) of the simple mixed element of Comparative Example 1 under a luminance of 15000 cd / m 2

114: Current luminous efficiency (27 cd / A) of the double stacked element of Comparative Example 2 under a luminance of 15000 cd / m 2

121: Maximum half-width of the electroluminescent peak of the sandwich mixed device of Example 1 at 10 V applied voltage (FWHM: 65 nm)

122: Center wavelength (λ _c : 513 nm) of the electroluminescent peak of the sandwich-mixed device of Example 1 at 10 V applied voltage

Claims (21)

Formed on the substrate First electrode, A second electrode facing the first electrode, and A phosphorescent organic light emitting diode comprising a light emitting layer positioned between the first electrode and the second electrode, Each of the light emitting layers includes a light emitting host consisting of a hole transporting light emitting host, a mixed light emitting host, and an electron transporting light emitting host, wherein the light emitting host is a mixed mixture of these hosts between the hole transporting light emitting host and the electron transporting light emitting host. It has a sandwich mixture structure where the light emitting host is located. The hole-transmitting light emitting host includes at least one selected from the group consisting of TCTA, CBP, NPB, PPP and PPV, The electron transmitting light emitting host includes at least one selected from the group consisting of TAZ, TPBI, Balq, PH1, Bphen, Bebq2, PPP, and PPV, The phosphorescent organic light emitting diode further comprises at least one of a hole transport layer between the first electrode and the light emitting layer, and an electron transport layer located between the second electrode and the light emitting layer, and between the electron transport layer and the light emitting layer. A hole blocking layer positioned between the hole blocking layer and a hole injection layer positioned between the hole transport layer and the first electrode, The mixed light emitting host is a phosphorescent organic light emitting diode, characterized in that it comprises a mixture of a hole transfer light emitting host and an electron transfer light emitting host mixed in a weight ratio of 3: 1 to 1: 3. delete The phosphorescent organic light emitting diode of claim 1, wherein each of the hole transporting light emitting host, the mixed light emitting host, and the electron transporting light emitting host comprises a phosphorescent dopant having a uniform concentration. The phosphorescent organic light emitting diode of claim 1, wherein the hole-transmitting light emitting host, the mixed light emitting host, and the electron transporting light emitting host each include a phosphorescent dopant having a non-uniform concentration. The phosphorescent organic light emitting diode of claim 3 or 4, wherein the hole transporting light emitting host, the mixed light emitting host, and the electron transporting light emitting host are fluorescent materials, and the dopant is a phosphorescent material. The phosphorescent organic light emitting diode of claim 3 or 4, wherein the hole transporting light emitting host, the mixed light emitting host, and the electron transporting light emitting host and the dopant are phosphorescent materials, respectively. delete delete The phosphorescent organic light emitting diode of claim 3 or 4, wherein the dopant is any one selected from the group consisting of an organic light emitting low molecular material, an organic light emitting polymer, and an organic light emitting oligomer. The method of claim 9, wherein the dopant is Ir (ppy) ₃ , Ir (tpy) ₃ , Ir (thpy) ₃ , Ir (piq) ₃ , Ir (fliq) ₃ , Ir (tiq) ₃ , Ir (flpy) ₃ At least one selected from the group consisting of Ir (btpy) ₃ , (pq) ₂ Ir (acac), (btp) ₂ Ir (acac), (F ₂ ppy) ₂ Ir (pic), FIr (pic) and PtOEP To include, phosphorescent organic light emitting diode. The phosphorescent organic light emitting diode of claim 1, wherein the light emitting layer has a thickness of 10 nm to 100 nm. The phosphorescent organic light emitting diode of claim 1, wherein the first electrode is an anode and the second electrode is a cathode. The phosphorescent organic light emitting diode of claim 1, which is a green phosphorescent organic light emitting diode. The phosphorescent organic light emitting diode of claim 1, which is a red phosphorescent organic light emitting diode. The phosphorescent organic light emitting diode of claim 1, wherein the phosphorescent organic light emitting diode is a blue phosphorescent organic light emitting diode. A phosphorescent organic light emitting diode according to claim 1, which is a yellow phosphorescent organic light emitting diode. delete Forming a first electrode on the substrate; Forming a light emitting layer on the first electrode; And Forming a second electrode on the light emitting layer; Forming the light emitting layer includes laminating a hole transporting light emitting host layer, a mixed light emitting host layer, and an electron transporting light emitting host layer sequentially on a first electrode, Forming a hole injection layer and a hole transport layer between the step of forming the first electrode and the step of forming the light emitting layer; And forming a hole blocking layer and an electron transporting layer between the forming of the light emitting layer and the forming of the second electrode. The hole-transmitting light emitting host includes at least one selected from the group consisting of TCTA, CBP, NPB, PPP and PPV, The method of manufacturing a phosphorescent organic light emitting diode according to claim 1, wherein the electron transmitting light emitting host comprises at least one selected from the group consisting of TAZ, TPBI, Balq, PH1, Bphen, Bebq2, PPP, and PPV. The method of claim 18, wherein the mixed light emitting host layer comprises a mixture of a hole transporting light emitting host and an electron transporting light emitting host mixed in a weight ratio of 3: 1 to 1: 3. The method of claim 18, wherein the light emitting layer is formed by any one method selected from the group consisting of a vacuum deposition method, a spin coating method and an inkjet printing method. The method of claim 18, wherein the hole transport layer comprises at least one material selected from the group consisting of DNTPD, NPD, NPB, TCTA and CBP, The electron transport layer comprises at least one material selected from the group consisting of SFC137, Alq3, BCP, Balq and Bphen, a method of manufacturing a phosphorescent organic light emitting diode.

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