KR101611668B1 - Use of heavy metal or compound comprising the same in blue organic electronic device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting device using a compound containing heavy metal or heavy metal.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a blue organic light emitting diode (OLED)

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blue organic light emitting device to which a heavy metal or a compound containing the same is applied.

The present application claims the benefit of Korean Patent Application No. 10-2013-0108003 filed on September 9, 2013, filed with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference.

Organic light emitting devices are attracting attention for flexible and large area display light emitting applications.

Fluorescent organic light emitting devices utilize electroluminescence resulting from singlet excitons.

According to the spin statistics, carrier recombination produces singlet and triplet excitons at a ratio of 1: 3. In the case of general aromatic compounds, triplet excitons are emitted only at extremely low temperatures And a radiative decay occurs.

However, delayed fluorescence can also occur in a fluorescent device through triplet-triplet annihilation.

Phosphorus, the direct radioactive decay of triplet excitons, was first implemented using iridium phenylpyridine complexes. 75, 4-6 (1999)), which is a high-effieiency green organic light-emmiting device based on electrophosphorescence. Appl. Phys. Lett.

The efficient spin-orbital coupling effect of iridium was used to obtain an efficient decay rate of radioactive decay (~ 10 ⁶ / s ^-1 ).

This has no problem in reaching a theoretical internal quantum efficiency of 100%.

However, in the case of a blue phosphorescent device, the lifetime of the device is remarkably small, which has limitations in practical applications.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device using a compound containing a heavy metal or heavy metal to drastically increase internal quantum efficiency.

Baldo, M. A., Lamansky, S., Burrows, P. E., Thompson, M. E. & Forrest, S. R. Very high-effieiency green organic light-emmiting devices based on electrophosphorescence. Appl. Phys. Lett. 75, 4-6 (1999)

An object of the present invention is to provide a blue organic light emitting device using heavy metals or compounds containing them.

In one embodiment of the present disclosure, the first electrode; A second electrode facing the first electrode; And at least one organic layer including a light emitting layer provided between the first electrode and the second electrode,

The light emitting layer may include a light emitting material; And compounds comprising heavy metals or heavy metals,

And emits blue light.

The triplet energy level of the heavy metal complex contained in the light emitting layer according to one embodiment of the present invention is higher than the triplet energy level of the host of the light emitting layer. Therefore, the exciton produced in the host is not diffused into the heavy metal complex.

However, compounds containing heavy metals or heavy metals play a role in inducing a spin-orbital coupling effect on the triplet exiton of the host (EML host). That is, compounds containing heavy metals or heavy metals stimulate the triplet exitons of the host to radiatively decay. In addition, when a fluorescent dopant is applied, the host's singlet or triplet excitons are capable of transferring foster energy to a singlet state of the fluorescent dopant. Do. Accordingly, the organic light emitting device including the heavy metal complex has high blue fluorescence efficiency and / or long lifetime.

1 to 5 are cross-sectional views illustrating the structure of an organic light emitting device according to an embodiment of the present invention.
6 is a diagram showing the energy level of a host / dopant and the energy level of a heavy metal complex in the light emitting layer.
7 is a graph showing electroluminescence (EL) spectra of Examples 1 to 3 and Comparative Example 1. Fig.
8 is a diagram showing photoluminescence (PL) of the light emitting layer films of Example 4 and Comparative Example 2;

Hereinafter, the present specification will be described in detail.

In one embodiment of the present disclosure, the first electrode; A second electrode facing the first electrode; And at least one organic layer including a light emitting layer provided between the first electrode and the second electrode,

The light emitting layer may include a light emitting material; And a compound containing a heavy metal or heavy metal, and which emits blue light.

In the present specification, the light emitting material refers to any material that can form an exciton in an organic light emitting device and emit light when the exciton falls to a ground state. The light emitting material may be used alone, Dopants can be used together.

In one embodiment of the present invention, the luminescent material includes a host and a dopant.

In one embodiment of the present invention, the triplet energy level of the compound containing the heavy metal is greater than the triplet energy of the light emitting material.

In one embodiment of the present invention, the triplet energy level of the compound containing heavy metals is 0.1 eV to 5 eV greater than the triplet energy of the light emitting material. In one embodiment of the present invention, the triplet energy level of the heavy metal-containing compound is 0.1 eV to 2 eV greater than the triplet energy of the light emitting material.

In one embodiment of the present disclosure, the triplet energy level of the heavy metal-containing compound is 0.1 eV to 5 eV greater than the triplet energy of the dopant.

When the triplet energy of the compound containing the heavy metal according to an embodiment of the present invention is larger than the triplet energy of the light emitting material or the host and the dopant, the triplet exciton of the light emitting material or the host and the dopant includes heavy metals It is not diffused into the compound.

In one embodiment of the present invention, the compound containing a heavy metal or heavy metal does not emit light in the organic light emitting device. However, the heavy metal or heavy metal compound stimulates the triplet exiton of the host to radiatively decay to induce a spin-orbital coupling effect.

In one embodiment of the present disclosure, the heavy and heavy metal compounds induce an intermolecular spin-orbital coupling effect on the triplet exciton of the host.

As a result of inducing the spin-orbital coupling effect of the triplet exciton of the host, the triplet exiton of the host is radiatively decayed. In this case, the triplet excitons of the host can be transferred to a singlet state of the dopant by Foster energy transfer.

Generally, in the case of an organic light emitting device, a triplet exciton is diffused into a phosphorescent dopant and radiative decay occurs due to a spin-orbital coupling effect.

In this specification, the compounds including heavy metals and heavy metals can be used in a fluorescent organic light emitting device using a fluorescent dopant, and indirectly cause a spin-orbital effect to the triplet exciton of the host. 6 is a diagram showing the energy level of a host / dopant and the energy level of a heavy metal complex in the light emitting layer.

In one embodiment of the present disclosure, the heavy metal and heavy metal compounds can be used in an organic light emitting device that does not use a fluorescent dopant, indirectly causing a spin-orbital effect on the triplet exciton of the host, Device may be provided.

In one embodiment of the present disclosure, the heavy metal complex is from 1 w% to 50 w% based on the host, and the dopant is from 0.1 w% to 10 w%.

In one embodiment of the present invention, the heavy metal includes one or more selected from the group consisting of Ir, Pt, Pd, Tb, Os, and Eu.

In one embodiment of the present disclosure, the dopant comprises a blue fluorescent dopant.

In one embodiment of the present invention, the heavy metal-containing compound includes one or more heavy metals selected from the group consisting of Ir, Pt, Pd, Tb, Os and Eu.

In one embodiment of the present disclosure, the heavy metal-containing compound comprises a ligand that is covalently bonded to a heavy metal.

In one embodiment of the present disclosure, the heavy metal complex comprises a ligand having a carbene structure.

In the present specification, the carbene means a structure containing a divalent carbon atom, that is, a structure containing two bonds out of four carbon bonds capable of bonding with other atoms.

When a ligand having the above carbene structure is included, the synthesis of a heavy metal complex having a high triplet energy level is easy and structurally stable.

As a heavy metal complex containing a ligand having a carbene structure according to an embodiment of the present invention, generally known ligands can be used. For example, a heavy metal complex containing a ligand having a carbene structure described in Korean Laid-Open Publication Nos. 2007-0090953, 2007-0053273, 2010-0045462, and 2010-0090259 can be used.

The fluorescent light-emitting layer may be formed of a material selected from the group consisting of distyrylarylene (DSA), distyrylarylene derivative, distyrylbenzene (DSB), distyrylbenzene derivative, DPVBi (4,4'- -diphenyl vinyl) -1,1'-biphenyl, DPVBi derivatives, spiro-DPVBi and spiro-6P (spiro-sexyphenyl).

The fluorescent light emitting layer is selected from the group consisting of a styrylamine type, a pherylene type, and a distyrylbiphenyl (DSBP) type as a dopant material.

In one embodiment of the present invention, the organic light emitting device further includes one or more layers selected from the group consisting of a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, an electron blocking layer and a hole blocking layer do.

For example, the structure of the organic light emitting device according to the present invention is illustrated in FIGS.

FIG. 1 illustrates the structure of an organic light emitting device in which an anode 2, a light emitting layer 5, and a cathode 7 are sequentially stacked on a substrate 1.

2 illustrates the structure of an organic light emitting device in which an anode 2, a light emitting layer 5, an electron transport layer 6, and a cathode 7 are sequentially laminated on a substrate 1. In FIG.

3 illustrates a structure of an organic light emitting device in which an anode 2, a hole transporting layer 4, a light emitting layer 5, an electron transporting layer 6, and a cathode 7 are sequentially laminated on a substrate 1.

4 illustrates the structure of an organic light emitting device in which an anode 2, a hole injecting layer 3, a hole transporting layer 4, a light emitting layer 5, and a cathode 7 are sequentially stacked on a substrate 1.

5 shows an organic light emitting device in which an anode 2, a hole injecting layer 3, a hole transporting layer 4, a light emitting layer 5, an electron transporting layer 6 and a cathode 7 are sequentially laminated on a substrate 1 Structure is illustrated.

In one embodiment of the present disclosure, the first electrode is an anode and the second electrode is a cathode. In another embodiment, the second electrode is a cathode and the first electrode is an anode.

The production of an organic light emitting device according to one embodiment of the present invention will be described in detail in the following examples. However, the following examples are intended to illustrate the present specification, and the scope of the present specification is not limited thereto.

[Example 1]

The device structure: ITO / HAT-CN (50 Å) / NPB (1,000 Å) HT1 (250 Å) / TCTA + XBD-370 4% + TPI 5% / ET-1 / ET-

Hexanitrile hexaazatriphenylene (HAT-CN) was thermally deposited on the ITO electrode to a thickness of 50 Å. Subsequently, a hole transport layer (p-type organic layer) was formed by vacuum evaporation of 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPB) .

The light-emitting layer was formed by doping tris (4-carbazoyl-9-ylphenyl) amine (TCTA) host with tris (2,4-pentanedionato) iridium 1 material was deposited as an electron transport layer and an ET-2 material was deposited on a 100 Å thick n-type dopant, Li (Li), as an electron transport layer, and doped with 2,4-pentanedionato iridium (TPI) And 1 wt%, respectively, to form an n-type doped layer.

In the above process, the deposition rate of the organic material was maintained at 0.5 to 2 Å / sec, the deposition rate of aluminum was maintained at 2 Å / sec, and the degree of vacuum during deposition was maintained at 2 × 10 ^-7 to 4 × 10 ^-8 mtorr Thus, an organic light emitting device was fabricated.

[LINE]

[NPB]

[HT-1]

[TCTA]

[TPI]

[BD-1]

[ET-1]

[ET-2]

[Example 2]

A device was fabricated in the same manner as in Example 1, except that the concentration of TPI was changed to 10 w% in Example 1.

[Example 3]

A device was fabricated in the same manner as in Example 1, except that the TPI concentration in Example 1 was 20w%.

[Comparative Example 1]

A device was fabricated in the same manner as in Example 1, except that TPI was included in the above-mentioned Example 1.

The current-voltage-luminance (IVL) characteristics of the devices manufactured according to Examples 1 to 3 and Comparative Example 1 are summarized in Table 1.

As shown in Table 1, when the light emitting layer is doped with TPI of 5% or more, it can be confirmed that CIE-y is shifted.

7 is a graph showing electroluminescence (EL) spectra of Examples 1 to 3 and Comparative Example 1. Fig.

As shown in FIG. 7, it can be seen that there is emission in the triplet of the TCTA host.

variable Voltage
(V) Current efficiency
(Cd / A) Luminous efficiency
(lm / A) Quantum efficiency
(QE) Color coordinates
(CIE-x) Color coordinates
(CIE-y) Example 1 TCTA + XBD 4% + TPI 5% 4.18 0.7 0.53 0.61 0.147 0.159 Example 2 TCTA + XBD 4% + TPI 10% 4.31 0.48 0.35 0.4 0.149 0.171 Example 3 TCTA + XBD 4% + TPI 20% 4.66 0.32 0.22 0.25 0.151 0.185 Comparative Example 1 TCTA + XBD 4% 4.11 1.78 1.36 1.85 0.139 0.126

 [Example 4]

In order to confirm that the radiative decay occurs at room temperature in the triplet of TCTA, the photoluminescence (PL) of the TCTA film and TPTA 10% doped TCTA film was measured.

[Comparative Example 2]

The photoluminescence of the TCTA film was measured in the same manner as in Example 4, except that the TPI was included in the above Example 4.

8 is a diagram showing photoluminescence (PL) of the light emitting layer films of Example 4 and Comparative Example 2;

As shown in FIG. 8, a wide shoulder peak can be observed in a region of 450 nm or more in the TPI-doped film.

Also, the triplet energy measured at film PL is lower than the value measured at low temperature (2.8 eV) can be understood as an activated result of phonon mode at room temperature.

With the CIE-y shift of the EL spectrum of the device shown in Example 1 and the presence of a shoulder peak of PL in Example 4, the intermolecular ) Spin-orbital coupling shows that the triplet of the host is radioactive decay.

Therefore, the organic light emitting device including a heavy metal or a heavy metal compound according to one embodiment of the present invention has an internal quantum efficiency exceeding 25%, which is the limit of the quantum efficiency in the conventional blue fluorescent organic light emitting device, The implementation of a near blue organic light emitting device may be possible.

1: substrate
2: anode
3: Hole injection layer
4: hole transport layer
5: light emitting layer
6: electron transport layer
7: cathode

Claims (13)

A first electrode; A second electrode facing the first electrode; And at least one organic layer including a light emitting layer provided between the first electrode and the second electrode,
The light emitting layer may include a light emitting material; And compounds comprising heavy metals or heavy metals,
Wherein the luminescent material comprises a host and a dopant,
Wherein the dopant comprises a blue fluorescent dopant,
The compound containing heavy metals and heavy metals is a non-derivatized material in the organic light emitting device,
Wherein the organic light emitting element emits blue light. delete delete The method according to claim 1,
Wherein the triplet energy level of the heavy metal-containing compound is 0.1 eV to 5 eV larger than the triplet energy of the light emitting material. The method according to claim 1,
Wherein the triplet energy level of the heavy metal-containing compound is 0.1 eV to 5 eV greater than the triplet energy of the dopant. The method according to claim 1,
Wherein the heavy metal or heavy metal compound induces spin-orbital coupling of the triplet exciton of the host. The method according to claim 1,
Based on the host
The heavy metal or heavy metal-containing compound is 0.1w% to 50w%
And the dopant is 0.1 w% to 10 w%. The method according to claim 1,
Wherein the heavy metal comprises one or two or more selected from the group consisting of Ir, Pt, Pd, Tb, Os and Eu. The method according to claim 1,
Wherein the heavy metal-containing compound comprises one or more heavy metals selected from the group consisting of Ir, Pt, Pd, Tb, Os and Eu. The method according to claim 1,
Wherein the heavy metal-containing compound comprises a ligand having a carbene structure. The method according to claim 1,
Wherein the heavy metal-containing compound comprises a ligand which is covalently bonded to a heavy metal. delete The method according to claim 1,
Wherein the organic light emitting device further comprises one or more layers selected from the group consisting of a hole injecting layer, a hole transporting layer, an electron transporting layer, an electron injecting layer, an electron blocking layer, and a hole blocking layer.

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