KR100261538B1 - Organic light emitting device having perylene/polyetherimide layer and the preparation thereof - Google Patents

Abstract

PURPOSE: An organic light-emitting device having perylene/polyetherimide layer and a preparation method thereof are provided to enhance the reliability and be capable of color adjustment by distributing the perylene of light-emitting material into thermally stable soluble polyetherimide to form an organic light-emitting layer. CONSTITUTION: The organic light-emitting device comprises a flat glass(1), a transparent anode(2), an organic light-emitting layer(3), an electron implantation electrode(4), and a DC source(5). The organic light-emitting layer(3) is composed of perylene and polyetherimide. Solution in which the perylene and polyetherimide are solved with the weight ratio of 5:95-60:40 and the concentration of 0.3-10 wt% into solvent is coated on the transparent anode(2), thereby forming the organic light-emitting layer(3).

Description

Organic electroluminescent device having perylene / polyetherimide light emitting layer and manufacturing method thereof

The present invention relates to a colorable organic electroluminescent device having improved reliability and a method for manufacturing the same, and specifically, to form a light emitting layer by dispersing perylene in soluble polyetherimide.

Among the organic light-emitting devices developed in the related art, color-tunable systems include doping about 2% of a monomolecular light emitting material with different colors, and PVK (poly (N-vinylcarbazole)) and There is a method of manufacturing by mixing a light emitting monomolecular material or a light emitting polymer material with the same non-luminescent or low luminous efficiency. However, the monomolecular and polymeric materials attempted to adjust the color in conventional organic light emitting devices are unstable materials having low heat resistance and oxidation resistance, and the reliability problem of the devices has been continuously raised.

Accordingly, an object of the present invention is to produce a color-definable light emitting device having improved reliability by dispersing perylene as a light emitting material in a thermally stable solution-soluble soluble polyetherimide to produce an organic light emitting layer.

1 shows a structure of an organic electroluminescent device according to an embodiment of the present invention;

FIG. 2 is a graph showing a change in current density according to an applied voltage of an organic electroluminescent device having a light emitting layer made of perylene only (FIG. 2A: linear-linear graph, FIG. 2B: linear-log graph);

3 is a graph showing a change in electroluminescence intensity according to an applied voltage of an organic electroluminescent device having a light emitting layer made of perylene only (FIG. 3A: linear-linear graph, FIG. 3B: linear-log graph);

Figure 4 is a graph showing the change in electroluminescence intensity according to the current density of the organic electroluminescent device having a light emitting layer of only perylene (Fig. 4a: linear-linear graph, Fig. 4b: log-log graph);

5 is a graph showing a change in current density according to an applied voltage of an organic electroluminescent device having a perylene / polyetherimide light emitting layer according to an embodiment of the present invention (FIG. 5A: linear-linear graph, FIG. 5B: linear-log Graph);

6 is a graph showing a change in electroluminescence intensity according to an applied voltage of an organic electroluminescent device having a perylene / polyetherimide light emitting layer according to an embodiment of the present invention (FIG. 6A: linear-linear graph, FIG. 6B: linear- Log graph);

7 is a graph showing the change in electroluminescence intensity according to the current density of the organic electroluminescent device having a perylene / polyetherimide light emitting layer according to an embodiment of the present invention (Fig. 7a: linear-linear graph, Fig. 7b: log- Log graph).

* <Explanation of symbols for main part of drawing>

1: flat glass substrate 2: transparent electrode

3: perylene / polyetherimide organic light emitting layer

4 metal electrode 5 DC power

Accordingly, the present invention provides an organic light emitting device comprising an anode transparent electrode, an organic light emitting layer, and an electron injection electrode, wherein the organic light emitting layer is made of perylene and polyetherimide.

Further, according to the present invention, in the method of manufacturing an organic electroluminescent device comprising an anode transparent electrode, an organic light emitting layer and an electron injection electrode, the perylene and soluble polyetherimide solvent in a weight ratio of 5:95 to 60:40 It provides a method for forming an organic light emitting layer by coating a solution dissolved in a concentration of 0.3 to 10% by weight on the transparent electrode.

Hereinafter, the present invention will be described in detail.

In the organic electroluminescent device of the present invention, the anode transparent electrode may be manufactured by coating ITO (indium titanium oxide) on a glass substrate by a conventional method.

In manufacturing the organic light emitting layer of the organic electroluminescent device of the present invention, a host-guest structure using a polymer as a host is used to maintain stability. The present invention is characterized by using a soluble poly (etherimide) having a repeating unit represented by the following formula (1) as a host in the organic light emitting layer, and using perylene represented by the following formula (2) as an organic light emitting material which is a guest.

It is preferable that the glass transition temperature of the said poly (etherimide) is 210 degreeC or more, and molecular weight is 40,000 or more.

The poly (etherimide) and perylene are mixed in a weight ratio of 95: 5 to 40:60, and the mixture is dispersed in a solvent at a concentration of 0.3 to 10% by weight to prepare a light emitting layer coating solution. In this case, chloroform, dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, or the like may be used as the solvent, and chloroform is preferable.

The luminescent solution dispersed in polyetherimide may be coated on an ITO-glass transparent electrode using any of the usual wet processes such as spin coating, doctor coating and screen printing, for example at 1,000 to 5,000 rpm. Spin coating may be performed for 1 to 5 minutes, and dried at 30 to 100 ° C. for 5 minutes to 1 hour or more to form a light emitting layer.

The organic electroluminescent device according to the present invention may be manufactured by placing the substrate coated with the organic light emitting layer in a vacuum chamber and depositing a cathode metal such as aluminum on the organic thin film.

The present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited only to the following examples.

Reference example: Organic light emitting device having a light emitting layer composed only of perylene

Perylene was thermally deposited on the ITO substrate under a vacuum of about 10 ⁻⁶ Torr. The thickness of the final thin film was about 200 nm and the deposition rate was 0.2 nm / sec. Aluminum was deposited at the same vacuum degree as a cathode on the prepared perylene thin film layer. The final thin film was about 500 nm thick and the deposition rate was 0.5 to 1.0 nm / sec.

The driving characteristics of the organic electroluminescent device fabricated as described above are shown in FIGS. 2, 3 and 4. 2 is a graph showing a change in current density according to an applied voltage of the organic electroluminescent device. 2A shows a linear-linear graph of current density values with respect to an applied voltage, in which charge injection by ohmic or thermonic is observed around 5-6 V, and charge injection by tunneling is dominant above about 10 V. This can be seen from the rise of the slope. A more accurate relationship can be seen when representing the logarithm of the current density on the Y-axis as shown in FIG. 2B, where the start of charge injection is about 2.5V and the boundary voltage between ohmic and tunneling is about 6V.

3 is a graph showing a change in electroluminescence intensity according to the applied voltage of the organic electroluminescent device. Comparing FIG. 3A (linear-linear graph) and FIG. 4B (linear-log graph), when the ON voltage is about 4.5V and about 12V, the increase in the emission intensity gradually decreases. The color of the electroluminescent light was red.

4 is a graph showing a change in electroluminescence intensity according to the current density of the organic electroluminescent device. Figure 4a is a linear-linear graph showing the light emission intensity value for the current density, Figure 4b is a log-log graph. In FIG. 4A, the slope of the current density is changed around 0.2 mA / cm ² so that the contribution of the current density is divided into two sections (a, b). To be more specific, as shown in FIG. 4B, a step of injecting light but not emitting light (c), a low light emission contribution (dominant ohmicity) (d), and a high light emission contribution (tunneling are dominant) (E) appears in about three sections.

Example organic light emitting device having a perylene / polyetherimide light emitting layer

Perylene and soluble polyetherimide were dissolved in chloroform at a weight ratio of 40:60, and stirred at a concentration of about 0.5% by weight for about 24 hours to prepare a coating solution. The prepared solution was spin coated onto a prepared ITO substrate. Spin coating was performed for about 3 minutes at 3,000 rpm. The spin coated thin film was dried at about 45-50 ° C. for at least 1 hour. The thickness of the final thin film was about 60 nm. Aluminum as a cathode was deposited on the organic thin film layer prepared above at a vacuum degree of 10 ⁻⁶ Torr. The thickness of the final thin film was about 500 nm.

The structure of the organic electroluminescent device of the present invention prepared as described above is shown in FIG.

The driving characteristics of the organic electroluminescent device of the present invention manufactured as described above are shown in FIGS. 5, 6 and 7. 5 is a graph showing a change in current density according to an applied voltage of an organic light emitting diode according to an embodiment of the present invention. 5A shows a linear-linear graph of the current density value with respect to the applied voltage, which shows a similar behavior to the diode characteristic, and as soon as voltage is applied as shown in the Y-axis, the logarithm of the current density as shown in FIG. 5B. As the leakage current increased, the current flow increased at a constant slope at about 1 V.

FIG. 6 is a graph illustrating a change in electroluminescence intensity according to an applied voltage of an organic electroluminescent device according to an embodiment of the present invention. As shown in FIG. 6, a turn-on voltage for detecting photons by an electroluminescent process is identified. Can be. In FIG. 6A, the luminous intensity values of the applied voltages are shown in a linear-linear graph. Although photons can be detected at about 5-6 V, the logarithmic intensity of the luminous intensity is represented by the Y axis as shown in FIG. 6B. Since the photon was observed from V, it can be seen that the accurate ON voltage of the light emitting device is about 3 volts. Above about 5 V, bright yellow electroluminescent light was clearly observed even under room light.

7 is a graph showing the change in electroluminescence intensity according to the current density of the organic electroluminescent device according to an embodiment of the present invention. Figure 7a is a linear-linear graph showing the light emission intensity value for the current density, Figure 7b is a log-log graph. In FIG. 7A, four sections are divided according to the contribution of the injected charge. The four sections are sections (a) without luminescent contributions, sections (b) with low luminous contributions, sections (c) with high luminous contributions, and sections (d) where light is gradually decayed. Here, in particular, since the light emission gradually decreases at a current density of about 75 mA / cm ² or more, this current density may be referred to as the critical current density of the present device. However, in FIG. 7B, the divisions of the sections b and c of FIG. 7A are not clearly divided but are divided into three sections as a whole (sections e, f, and g).

The present invention can be used not only for the organic light emitting device but also for the fabrication of FET (Field Effect Transister), photodiode, solar cell, and the like. The present invention is also applicable to the manufacture of fluorescent color filters.

According to the present invention, by dispersing perylene, a red monomolecular luminescent material, on a molecular level in a soluble polyetherimide having excellent thermal stability and processability to form a light emitting layer, the emitted light is shifted toward the blue wavelength and the light emitting color is changed to yellow instead of red. The adjusted organic electroluminescent device can be fabricated, and the light emitting device of the present invention also has excellent reliability of driving characteristics of the device.

Claims (5)

An organic electroluminescent device comprising an anode transparent electrode, an organic light emitting layer, and an electron injection electrode, wherein the organic light emitting layer is made of perylene and soluble polyetherimide. The method of claim 1, The soluble polyetherimide has a repeating unit of the following formula. Formula 1

The method of claim 1, A light emitting device comprising perylene and a soluble polyetherimide in a weight ratio of 5:95 to 60:40. In the method of manufacturing an organic electroluminescent device comprising an anode transparent electrode, an organic light emitting layer and an electron injection electrode, 0.3 to 10% by weight of perylene and soluble polyetherimide in an organic solvent in a weight ratio of 5:95 to 60:40 A method of manufacturing an organic electroluminescent device, comprising forming an organic light emitting layer by coating a solution dissolved at a concentration on the transparent electrode. The method of claim 4, wherein The organic solvent is chloroform.

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