KR20140043036A - Organic metal compound and organic electroluminescent device comprising the same - Google Patents

Abstract

The present invention relates to an organic electroluminescent device comprising two different kinds of organic metal compounds, represented by the chemical formula 1, in a light emitting layer. The organic electroluminescent device comprising the light emitting layer having the two different kinds of organic metal compounds as a mixed dopant according to the present invention has outstanding luminance and color purity characteristics, thereby can be used for a display or a lighting. [Reference numerals] (AA) Luminous efficiency(cd/A); (BB) Second dopant weight ratio

Description

Organic metal compound and organic electroluminescent device comprising the same

The present invention relates to an organic metal compound and an organic light emitting device comprising the same, and more particularly, to an organic light emitting device having excellent color purity, brightness, and lifetime characteristics by including two different types of organic metal compounds in a light emitting layer. .

Recently, organic light emitting diodes have been spotlighted as next-generation display devices due to their advantages such as thin, wide viewing angle, light weight, small size, fast response speed, and low power consumption compared to cathode ray tubes (CRTs) and liquid crystal devices (LCDs).

However, although the organic light emitting device is gradually expanding its application field to the display and lighting field of various electronic products, the efficiency and lifespan characteristics are restricting the expansion of the application fields. But much research is being done in terms of materials. In particular, in order to maximize the luminous efficiency in terms of materials, a dopant is mainly composed of a structure doped with a host, and a host-dopant system adopts a light emission by transferring electrons and holes to the dopant through the host. Development of a host compound capable of maximizing the light emitting properties of the dopant and the dopant is being actively made.

However, the conventional technology is composed of a light emitting layer of a single host and a single dopant, the inventors of the present invention developed an organic light emitting device having a more improved color purity and luminous efficiency using a mixed dopant.

Accordingly, the present invention provides an organic electroluminescent device employing a light emitting layer of a host-dopant system, wherein the dopant included in the light emitting layer is composed of two different types of organometallic compounds having a light emission peak difference of 50 nm or less. An organic electroluminescent device having further improved luminance characteristics is provided.

In order to solve the above problems,

A first electrode; A second electrode; And a light emitting layer comprising a first dopant and a second dopant between the first electrode and the second electrode, wherein the first dopant and the second dopant are different from each other and are independent of each other. An organic electroluminescent device characterized in that it is an organometallic compound represented by the following [Formula 1].

[Chemical Formula 1]

(Lig) _m M (X) _3-m

In Formula 1, Lig and X are unequal monoionic bidentate ligands, M is a metal forming an octahedral complex, and m is an integer of 0 to 3.

The light emission peak difference between the first dopant and the second dopant organometallic compound is not more than 50 nm.

In addition, the weight ratio of the first dopant and the second dopant may be 50-99: 1-50.

According to the present invention, an organic light emitting display device having a light emitting layer including two different organometallic compounds as a mixed dopant may be usefully used for display and lighting due to its excellent brightness and color purity characteristics. In addition, in manufacturing a large-area organic light emitting display device, it is possible to manufacture by using a solution process such as spin coating method or printing method, so the manufacturing process cost is low, and the first dopant having excellent color purity characteristics and excellent luminous efficiency are provided. By mixing and using the second dopant, various light emission characteristics can be optimally controlled and more efficient.

1A is a graph showing luminous efficiency according to the weight ratio of the second dopant in Example 1 (elements A to G).
FIG. 1B is a graph showing changes in color purity characteristics according to the weight ratio of the second dopant in Example 1 (elements A to G). FIG.
2 is an electroluminescence spectrum according to the weight ratio of the second dopant in Example 1. FIG.
3 is a graph showing a change in wavelength peak according to the weight ratio of the second dopant in Example 1.
4A and 4B are graphs showing a CIE 1391 color correspondence function and an RGB color correspondence function, respectively.
5A is a graph showing luminous efficiency according to the weight ratio of the second dopant in Example 2 (elements A to G).
5B is a graph showing changes in color purity characteristics according to the weight ratio of the second dopant in Example 2 (elements A to G).

Hereinafter, the present invention will be described in more detail based on the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. It will be clear to those who have knowledge.

The present invention relates to an organic light emitting device comprising a light emitting layer containing a mixed dopant of a first dopant and a second dopant between a first electrode and a second electrode, wherein the first dopant and the second dopant It is different from each other, and each independently is characterized by the organometallic compound represented by the following [Formula 1].

[Chemical Formula 1]

(Lig) _m M (X) _3-m

In Formula 1, Lig and X are unequal monoionic bidentate ligands, M is a metal forming an octahedral complex, and m is an integer from 0 to 3.

In addition, the light emission peak difference between the first dopant compound and the second dopant compound is 50 nm or less, the weight ratio of the first dopant and the second dopant is characterized in that 50-99: 1-50 do. When the first dopant is excellent in color purity but low in luminous efficiency, the second dopant is more efficient. By mixing such dopants in the weight ratio range, the color purity is maintained and the luminous efficiency is further increased. Is improved.

Example

In an embodiment according to the invention, the ITO transparent electrode is a square anode of four 2 mm × 2 mm in the center, using an ITO glass substrate with an ITO transparent electrode on a 50 mm × 50 mm × 0.7 mm glass substrate. It means a substrate manufactured through a photolithography process to form a pixel.

In addition, as an example of the first electrode and the second electrode, an ITO transparent electrode and an aluminum metal thin film were used. In the organic electroluminescent device, various device structures such as back emission and top emission are used. It will be apparent to one of ordinary skill in the art that the two electrodes are not limited to the cathode.

Example  One

As an embodiment of the present invention, a red light emitting organic light emitting device having the following device structure was manufactured, and light emission characteristics including light emission efficiency were measured.

ITO transparent electrode / PEDOT: PSS (60 nm) / hole transport layer (60 nm) / host compound RH1: first dopant compound (D1): second dopant compound (D2) (40 nm) / electron transport layer (33 nm ) / Liq (1 nm) / Al (100 nm)

PEDOT: PSS (AI4083), which is widely used as a hole injection layer in an ITO transparent electrode, was formed by spin coating to have a thickness of about 60 nm. Then, the following compound TPD was formed by spin coating as a hole transport layer.

As the light emitting layer, [RH1] was used as the following host compound, and as the mixed dopant, the first dopant compound was used as the following [D1], and the second dopant compound was used as the following [D2], respectively. -pq): p: q, (p + q) = 7 using a solution prepared so as to form a thickness of about 40 nm by spin coating method, and further electron transport layer 33 nm and Liq 1 nm and aluminum 100 nm was formed into a film by the vapor deposition method, and the organic electroluminescent element was produced.

[RH1] [D1]

D2 (Ir (MDQ) 2acac) TPD

The obtained organic EL device measured voltage, current, and luminous efficiency by using a source meter (Model 237, Keithley) and a luminance meter (PR-650, Photo Research). And defined as ".

In addition, the current value was set so that the initial reference luminance was 800 cd / m 2 at room temperature, and the decrease change of the emission luminance in the direct current constant current driving was measured. In this embodiment, the time of 97% compared to the initial luminance is " T97 lifetime. And defined as ". The results are shown in the following [Table 1] and FIG. 1.

device Weight ratio
(p: q) Driving voltage
(V) Luminous efficiency
(Cd / A) CIEx CIEy Luminous Peak
(nm) life span
(T97, hrs) A 100: 0 6.3 5.6 0.674 0.323 628 7 B 70:30 5.7 5.9 0.669 0.327 626 28 C 50:50 5.5 6.6 0.665 0.331 625 27 D 30:70 5.6 7.3 0.660 0.337 624 23 E 20:80 5.9 7.7 0.653 0.344 623 37 F 10:90 5.9 8.2 0.645 0.351 620 31 G 0: 100 5.5 10.9 0.619 0.378 612 3

As shown in Table 1, in the case of <element A> using the first dopant compound D1 alone, the wavelength peak of the electroluminescence was 628 nm, indicating the red light emission characteristic, and the color purity characteristic of the red light emission. The x value of the CIE 1391 standard, which is mainly used, is 0.674, which is the largest, showing excellent color purity characteristics, but the lowest luminous efficiency.

On the other hand, in the case of <element G> using the second dopant compound D2 alone, the wavelength peak of the electroluminescence is 612 nm, which is about 16 nm smaller than the electroluminescence wavelength peak of the first dopant compound D1, and CIE x The smallest value is 0.619, so that the color purity characteristic is relatively poor, while the luminous efficiency is the highest.

In the embodiment according to the present invention, the weight ratio of the host compound is 93%, and the mixing ratio is changed under the condition that the sum of the weight ratios of the first dopant compound D1 and the second dopant compound D2 is 7% of the total weight. And used as the light emitting layer of the organic EL device.

At this time, when the first dopant compound D1 and the second dopant compound D2 are mixed, the luminescence properties represented by the respective compounds appear to be simply linearly proportional to the mixing weight ratio, but are actually nonlinear characteristics as shown in FIG. 3. It was confirmed that it represents.

Until the critical mixed weight ratio, that is, the first dopant compound and the second dopant compound is 50:50 (x: y = 50: 50), the color purity characteristic (CIE x) of the first dopant compound (D1) is almost maintained. When the weight ratio of the second dopant compound (D2) exceeds the critical mixing weight ratio (50%), it can be confirmed that the weight ratio is rapidly lowered.

On the other hand, the color purity characteristics of the red light-emitting component suitable for display is preferably such that the CIE x coordinate value is 0.66 or more, in the case of the organic electroluminescent device manufactured in the above embodiment according to the present invention, the first dopant compound (D1 It is preferable that the mixing weight ratio of the second dopant (D2) with respect to) does not exceed 50%. In this case, the light emission efficiency and lifetime characteristics are further improved while the color purity is preferably maintained.

In order to explain the principle of the mixed dopant according to the present invention in more detail, the electroluminescence spectrum of each of the comparison elements according to the weight ratio of the second dopant and the respective comparison according to the weight ratio of the second dopant The change in electroluminescence peak of the devices is shown. 4A and 4B are graphs showing a CIE 1391 color matching function and an RGB color matching function, respectively.

For the second dopant compound (D2) of the example, the electroluminescence wavelength peak is 612 nm, which is similar to the maximum of the x function (or r function of the RGB color correspondence function) of the CIE 1391 color correspondence function, while the x function As it approaches the maximum value of, the luminous efficiency increases and the color purity deteriorates.

When the first dopant compound (D1) having an electroluminescent wavelength peak of 628 nm is mixed with the second dopant compound (D2), the wavelength peak and the spectral shape of the 500-600 nm region are adjusted to maintain an appropriate color purity. The luminous efficiency can be increased.

Referring to the color-corresponding function of the CIE standard observer of FIG. 4 and the measured peak value of Table 1, in the case of the red light emitting organic light emitting diode, the wavelength peak of the second dopant is 600-620 nm and the first dopant. It can be seen that the wavelength peak of 620-670 nm can maximize the mixing effect, the peak difference between the electroluminescence wavelength of the first dopant and the second dopant is preferably within 50 nm.

This principle can be extended to a green light emitting organic light emitting device or a blue light emitting organic light emitting device, and in the case of a green light emitting device, the electroluminescent wavelength of the C function of the CIE 1391 color corresponding function of FIG. The first dopant and the second dopant having a peak difference of 50 nm are mixed, and in the case of a blue light emitting device, the first dopant and the second having a 50 nm peak difference in electroluminescence wavelength centered on the wavelength peak of the b function. It is desirable to select a dopant.

On the other hand, in the electroluminescence spectra of each of the comparative elements shown in FIG. 2, even when the mixing weight ratio of the first dopant compound (D1) and the second dopant compound (D2) is 30:70, the wavelength peak of the spectrum and It can be seen that the form does not change significantly.

In addition, the electroluminescence peak value of each of the comparative elements according to the weight ratio of the second dopant shown in FIG. 3 is compared with the color purity characteristic change of FIG. 1B, and the emission spectrum of the first dopant compound (D1) and the second plate It can be seen that the mixing effect of the emission spectrum of the compound (D2) is nonlinearly related to the mixing weight ratio.

In particular, the criticality of the first dopant compound (D1) and the second dopant compound (D2) in which the color purity characteristics of the first dopant compound (D1) are maintained even if the mixing weight ratio of the second dopant compound (D2) increases. The mixing weight ratio is 50:50.

Example  2

As another embodiment of the present invention, a red light emitting organic light emitting device having the following device structure was manufactured, and light emission characteristics including light emission efficiency were measured.

ITO transparent electrode / PEDOT: PSS (60 nm) / hole transport layer (20 nm) / host compound RH2: first dopant compound (D3): second dopant compound (D2) (50 nm) / electron transport layer (33 nm ) / Liq (1 nm) / Al (100 nm)

PEDOT: PSS (AI4083), which is widely used as a hole injection layer in an ITO transparent electrode, was formed by spin coating to have a thickness of about 60 nm, and then the following compound TFB was formed by spin coating as a hole transport layer.

As the light emitting layer, [RH2] is used as the following host compound, and as the mixed dopant, the first dopant compound is the following [D3] and the second dopant compound is the following [D2], respectively. 95-pq): using a solution prepared such that p: q, (p + q) = 5, the film was formed by spin coating to a thickness of about 50 nm, and further, an electron transport layer 33 nm and Liq 1 nm and 100 nm of aluminum was formed into a film by vapor deposition to manufacture an organic EL device.

[RH2] [D3]

[D2] (Ir (MDQ) 2acac) [TFB]

The obtained organic EL device measured voltage, current, and luminous efficiency by using a source meter (Model 237, Keithley) and a luminance meter (PR-650, Photo Research). And defined as ". In addition, the current value was set so that the initial reference luminance was 800 cd / m2 at room temperature, and the decrease change of the emission luminance in the DC constant current driving was measured. In this embodiment, the time which becomes 97% compared to the initial luminance is " T97 lifetime. And defined as ". The results are shown in the following [Table 2] and FIG. 5.

device Weight ratio
(p: q) Driving voltage
(V) EL Eff
(Cd / A) CIEx CIEy Luminous Peak
(nm) life span
(T97, hrs) A 100: 0 7.6 13.7 0.666 0.333 621 85.3 B 80:20 7.9 13.8 0.664 0.335 620 98.6 C 50:50 7.5 14.1 0.663 0.336 620 100 D 40:60 8.3 15.1 0.653 0.345 619 71.3 E 30:70 7.2 15 0.650 0.349 618 69.6 F 20:80 6.8 15.3 0.645 0.354 617 55.6 G 0: 100 7.2 17 0.625 0.373 612 80.3

In Example 2, compared with Example 1, the host compound and the first dopant compound were changed to compare the mixing properties of the second dopant compound (D2) applied in Example 1. As in Example 1, even when the mixing weight ratio of the second dopant compound (D2) increases, the first dopant compound (D3) and the second dopant compound ( The critical mixing weight ratio characteristic of D2) is 50:50.

In addition, in order to maximize the economic effect of the present invention, it is preferable that the wavelength peak difference between the first dopant and the second dopant is large. Decreases from 50:50.

Claims (3)

A first electrode; A second electrode; And a light emitting layer comprising a first dopant and a second dopant between the first electrode and the second electrode.
The first dopant and the second dopant are different from each other, each independently an organic electroluminescent device, characterized in that the organic metal compound represented by the following [Formula 1]:
[Chemical Formula 1]
(Lig) _m M (X) _3-m
In Formula 1, Lig and X are unequal monoionic bidentate ligands, M is a metal forming an octahedral complex, and m is an integer of 0 to 3. The method of claim 1,
The light emitting peak difference between the first dopant and the second dopant organometallic compound is 50 nm or less. The method of claim 1,
The organic light emitting device, characterized in that the weight ratio of the first dopant and the second dopant is 50-99: 1-50.

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