KR20230033456A - Light-emitting layer for high-efficiency organic light-emitting device and organic light-emitting device comprising same - Google Patents

Abstract

The present invention relates to a light emitting layer for an organic light emitting element having excellent efficiency and the organic light emitting element comprising the same. More specifically, the present invention relates to the light emitting layer for the organic light emitting element having a horizontal orientation rate that is high, and an improved efficiency and color purity by using a delayed fluorescent material comprising boron as a final light emitting body; and the organic light emitting element comprising the same. The light emitting layer for the organic light emitting element comprises: a first dopant compound; a second dopant compound; and a host compound.

Description

Light-emitting layer for high-efficiency organic light-emitting device and organic light-emitting device including the same

The present invention relates to a light emitting layer for an organic light emitting device having improved efficiency and color purity by using a compound containing boron and a polycyclic structure as a final light emitting body, and an organic light emitting device including the same.

Organic luminescence refers to a phenomenon in which electrical energy is converted into light energy using organic materials. At this time, the organic light emitting device is a device that emits light when electrical energy is applied by configuring an organic material in multiple layers between an anode and a cathode. The organic light emitting diode is composed of multiple organic layers for efficiency and stability, and may basically include a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer.

Materials used as organic layers can be divided into light emitting materials and charge transport materials according to their functions, and the light emitting materials are fluorescent materials using only fluorescence derived from a singlet excited state of electrons and derived from a triplet excited state according to a light emitting mechanism. It can be classified as a phosphor. also. The light emitting material can be divided into blue, green, and red light emitting materials according to the light emitting color, and phosphorescent materials are applied and used in the industry for the remaining colors except blue.

In the case of a blue light emitting material, only a single term is used due to limitations in lifespan and color characteristics, and only a fluorescent material with low efficiency is used. Therefore, as a blue light emitting material, a phosphorescent material using a triplet using a heavy metal such as iridium or platinum and a delayed fluorescent material using a triplet only as a pure organic material by making the energy difference between a singlet and a triplet small are being developed.

Unlike conventional fluorescence, in which 75% of triplet energy is lost using only singlet energy, phosphorescence uses heavy metals to induce spin state changes of electrons and intersystem crossing (ISC) to induce singlet and triplet energy. It is possible to achieve 100% internal quantum efficiency by using all of the term energy.

In delayed fluorescence, molecules are designed so that the energy difference between singlet and triplet is small, and triplet and singlet by inducing reverse intersystem crossing (RISC) phenomenon from triplet to singlet with only thermal energy at room temperature. All energy can be used. Therefore, since the triplet can be used like a phosphorescent material, the efficiency of the light emitting material is higher than that of the fluorescent material, and fluorescence emission is realized through the triplet, so it is named delayed fluorescence.

The characteristics of the organic light emitting device may depend on the dopant material of the light emitting layer, and the delayed fluorescence dopant is HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) to minimize the energy difference between singlet and triplet. should have little overlap. To this end, a donor-acceptor structure is mainly used, and in the case of the structure, intra-molecular charge transfer (Intra charge transfer) is possible. However, when a compound having a conventional donor-acceptor structure is applied to a delayed fluorescent material, there are disadvantages in that the emission wavelength shifts to a long wavelength region and the emission spectrum is wide and the color purity is inferior. Even in the case of phosphorescent materials, there is a limit in broadening the emission spectrum due to the charge transfer characteristics between the ligand and the central metal.

To overcome this, a delayed fluorescence or phosphor photosensitive fluorescent device using a conventional delayed fluorescent material or phosphorescent material as a host rather than a light emitting material and using a general fluorescent material having good color purity as a final light emitting material has been proposed. Delayed fluorescent materials convert almost all triplet excitons into singlet excitons using the reverse system transition process, and then transfer them to fluorescent materials through Forster energy transfer (FRET). Since excitons have properties similar to singlet excitons and energy transfer is possible through the same mechanism, a phosphor photosensitive fluorescent device can be manufactured. Accordingly, the fluorescent material can additionally use triplet exciton energy that has previously been lost and not used, and can realize high efficiency characteristics compared to conventional fluorescent materials. At the same time, since fluorescent materials have good color characteristics, poor color purity of conventional delayed fluorescence or phosphorescent materials can be improved.

However, when using a conventional fluorescent material as the final light emitting material, there is a limitation that the efficiency is lower than that of a phosphorescent or delayed fluorescent single material, which is because the triplet energy of the host material is lower or similar to the triplet energy value of the delayed fluorescent material. , or because the rate of reverse system transition of delayed fluorescence is not fast, the unconverted triplet exciton energy is non-luminescently transferred to a nearby fluorescent material through Dexter energy transfer (DET). In addition, if the Förster energy transfer efficiency is low, the singlet exciton utilization rate of the fluorescent material may be reduced, so that the fluorescent material cannot effectively use excitons. In addition, since the horizontal orientation ratio of the fluorescent material is not higher than that of the delayed fluorescent or phosphorescent material, the light extraction efficiency of the device is lowered, and thus the efficiency of the photosensitive fluorescent element generally does not exceed the efficiency of the delayed fluorescent material.

An object of the present invention is to improve the low efficiency of a conventional delayed fluorescence or phosphor photosensitive fluorescent device and to provide an organic light emitting device having high color purity characteristics.

In order to achieve the above object, a light emitting layer for an organic light emitting device according to an aspect of the present invention includes boron and a first dopant compound that is a delayed fluorescent material having a multi-resonance structure, a delayed fluorescent material or a phosphorescent material and a phosphorus second dopant compound and a host compound. Also, the singlet energy of the first dopant compound is S ₁ ^D1 , the triplet energy is T ₁ ^D1 , the singlet energy is S ₁ ^D2 , the triplet energy is T ₁ ^D2 , and the singlet energy of the host compound is S ₁ ^HOST , when the triplet energy is T ₁ ^HOST , the singlet energy relationship is S ₁ ^HOST > S ₁ ^D2 > S ₁ ^D1 , and the triplet energy relationship is T ₁ ^D2 > T ₁ ^D1 and T ₁ ^HOST > T ₁ ^D1 is satisfied, the first dopant compound includes boron and is a delayed fluorescent material having a multi-resonance structure, and the second dopant compound is a delayed fluorescent material or a phosphorescent material.

When the second dopant compound is a phosphor, a dopant having a Förster energy transfer rate from the second dopant compound to the first dopant compound faster than the light emission transfer rate of the second dopant compound may be used, and the second dopant compound is delayed. In the case of a fluorescent material, a dopant having a Förster energy transfer rate from the second dopant compound to the first dopant compound faster than a light emission transfer rate or a system-to-system transfer rate of the second dopant compound may be used.

A Förster energy transfer rate from the second dopant compound to the first dopant compound may be greater than or equal to 5×10 ⁷ s ⁻¹ .

A horizontal orientation ratio of the first dopant compound may be higher than a horizontal orientation ratio of the second dopant compound.

The light emitting layer for the organic light emitting device may include 0.1 to 3% by weight of the first dopant compound.

In the energy relationship, a potential difference between S ₁ ^D1 and T ₁ ^D1 may be 0.21 eV or less, the second dopant compound may be a delayed fluorescent material, and a potential difference between S ₁ ^D2 and T ₁ ^D2 may be 0.21 eV.

The first dopant compound may include a structure represented by Chemical Formula 1 below.

[Formula 1]

In Formula 1, ring A, ring B, ring C, and ring D are each independently a substituted or unsubstituted aryl ring or heteroaryl ring, and X ¹ , X ² , X ³ and X ⁴ are each independently O; NR or S, wherein R is a substituted or unsubstituted C ₆ -C ₂₀ aryl group, substituted or unsubstituted, bonded or unbonded to one or more of the A, B, C and D rings by a single bond; C ₂ -C ₂₀ heteroaryl group, substituted or unsubstituted C ₃ -C ₁₀ cycloalkyl group, substituted or unsubstituted C ₁ -C ₁₀ alkyl group, R ¹ and R ² are each independently hydrogen, deuterium, C ₁ -C ₆ alkyl group, C ₃ -C ₁₂ cycloalkyl group, C ₆ -C ₁₂ aryl group, C ₂ -C ₁₅ heteroaryl group, diarylamino group (wherein aryl is C ₆ -C ₁₂ aryl), cyano group, or it is halogen

A half height width of the first dopant compound may be narrower than a half height width of the second dopant compound.

The light emitting layer for the organic light emitting device may include the second dopant compound in a higher weight % than the first dopant compound.

An organic light emitting device according to another aspect of the present invention includes a first electrode, a second electrode provided to face the first electrode, and an organic material layer positioned between the first electrode and the second electrode, wherein the organic material layer is It is characterized in that it comprises a light emitting layer for an organic light emitting device according to the present invention.

A display device according to another aspect of the present invention is characterized in that it includes the organic light emitting element.

A lighting device according to another aspect of the present invention is characterized in that it includes the organic light emitting element.

The organic light emitting device of the present invention has high light extraction efficiency, effective energy transfer due to fast Forster energy transfer, and higher efficiency than conventional delayed fluorescence or phosphorescent devices and photosensitive fluorescent devices because it can prevent efficiency degradation due to DET, It has the characteristics of high color purity due to the narrow half-width characteristic.

1 is a diagram illustrating an example of an energy relationship between a dopant compound and a host compound satisfying the singlet energy relationship and the triplet energy relationship of the present invention.
2 shows the efficiency and electroluminescence spectrum of the device of Comparative Example 1 according to luminance.
3 shows the efficiency and electroluminescence spectrum of the device of Comparative Example 3 according to luminance.
4 shows the efficiency and electroluminescence spectrum of the device according to luminance of Example 2 of the present invention.
5 shows the efficiency and electroluminescence spectrum of the device according to the luminance of Example 3 of the present invention.
6 shows the efficiency and electroluminescence spectrum of the device according to luminance of Example 4 of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings.

Prior to this, the terms or words used in this specification and claims should not be construed as being limited to the usual or dictionary meaning, and the inventor appropriately uses the concept of the term in order to explain his/her invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined.

Therefore, the embodiments described in this specification and the configurations shown in the drawings are only one of the most preferred embodiments of the present invention, and do not represent all of the technical ideas of the present invention, so at the time of this application, they can be replaced. It should be understood that there may be many equivalents and variations.

An emission layer for an organic light emitting device according to an aspect of the present invention includes a first dopant compound having singlet energy S ₁ ^D1 and triplet energy T ₁ ^D1 ; A second dopant compound having a singlet energy of S ₁ ^D2 and a triplet energy of T ₁ ^D2 , and a host compound having a singlet energy of S ₁ ^HOST and a triplet energy of T ₁ ^HOST , wherein the singlet energy is S ₁ ^HOST > S ₁ ^D2 > S ₁ ^D1 , the triplet energies are T ₁ ^D2 > T ₁ ^D1 and T ₁ ^HOST > T ₁ ^D1 , and the first dopant compound includes boron and has a multi-resonance structure structure), it may have high color purity characteristics, and the second dopant compound is characterized in that it is a delayed fluorescent material or a phosphorescent material. 1 is a diagram illustrating an example of an energy relationship between a dopant compound and a host compound satisfying the singlet energy relationship and the triplet energy relationship, and arrows in FIG. 1 indicate paths through which excitons are transferred. When the singlet and triplet energy relationship between the host compound and the dopant compound is satisfied, most of the singlet and triplet excitons generated during device operation transfer the second dopant compound from the host compound through a Dexter or Förster energy transfer process. through and completely transferred to the first dopant compound, a highly efficient device can be fabricated. In addition, since the compound of the first dopant has a multi-resonant form including boron, it is possible to obtain emission spectrum characteristics of high color purity.

For efficient energy transfer, it is preferable that the Förster energy transfer rate from the second dopant compound to the first dopant compound is faster than the emission transfer rate or system-to-system transfer rate of the second dopant compound. The Förster energy transfer rate ( k _{FRET )} can be obtained according to Equations 1 and 2 below.

는 포스터 에너지 전이가 50% 발생할 수 있는 거리를 의미하며, 빠른 포스터 에너지 전이 속도를 위해서는 지연 형광 또는 인광 물질의 발광 스펙트럼과 최종 발광체의 흡수 스펙트럼 사이의 겹침(

)이 클수록 빠른 에너지 전이가 가능하다.of the above Equations 1 to 2

is the distance at which Förster energy transition can occur by 50%.

), the faster the energy transfer is possible.

When the second dopant is a phosphor and the Förster energy transfer rate is faster than the light emission transition rate of the second dopant compound, most singlet excitons generated in the second dopant compound do not directly emit light but are transferred directly to the first dopant compound. Therefore, the characteristics of high color purity and high efficiency of the light emitting layer can be realized.

In addition, when the second dopant compound is a delayed fluorescent material and the Förster energy transfer rate is faster than the luminescence transition rate or the interstitial transition rate of the second dopant compound, most of the singlet excitons generated from the second dopant compound directly emit or emit light. Since the second dopant compound can be completely transferred directly to the first dopant compound without undergoing an additional interphase/reverse interphase transition process, high color purity and high efficiency characteristics of the light emitting layer can be realized.

A Förster energy transfer rate from the second dopant compound to the first dopant compound may be 10 ⁶ s ⁻¹ to 10 ⁹ s ⁻¹ , and preferably 5×10 ⁷ s ⁻¹ or more. If the rate of Förster energy transfer from the second dopant compound to the first dopant compound is similar to or slower than the rate of light emission of the second dopant compound or the system-to-system transition rate in the case of delayed fluorescence, the singlet exciton is transferred to the first dopant compound rather than completely transferred to the first dopant compound. The two dopant compounds may emit light together, resulting in deterioration in color purity, and when the second dopant compound is delayed fluorescence, repeated system transition/reverse system transition processes may continue, resulting in deterioration in device characteristics. Therefore, when the Förster energy transfer rate from the second dopant compound to the first dopant compound is 10 ⁶ s ^-1 to 10 ⁹ s ^-1 , it may be faster than the luminescence rate or system-to-system transfer rate of the second dopant compound. When the Förster energy transfer rate from the dopant compound to the first dopant compound is 5 x10 ⁷ s ⁻¹ or more, stable high color purity and high efficiency characteristics of the light emitting layer may be easily realized.

The first dopant compound as the final light emitter preferably has a high horizontal orientation ratio, and in particular, the first dopant compound preferably has a higher horizontal orientation ratio than the second dopant compound. Since the singlet energy and triplet energy of the second dopant compound are higher than those of the first dopant compound, electrons (excitons) of the second dopant compound are transferred to the first dopant compound through Förster energy transfer, and the dopant receiving the exciton ( When the horizontal orientation ratio of the first dopant compound) is higher than that of the dopant (second dopant compound) giving exciton, the light extraction effect is increased, so that higher external quantum efficiency can be achieved even if the internal quantum efficiency is similar. For example, the horizontal orientation ratio of the first dopant compound may be 0.85 to 0.99, and the horizontal orientation ratio of the second dopant compound may be 0.50 to 0.90, but is not particularly limited thereto.

Even if the first dopant compound is doped in a small amount, energy transfer to the first dopant can sufficiently occur because the Förster energy transfer distance is sufficiently long. The efficiency of the light emitting layer may be increased by further increasing the photon efficiency. Specifically, the first dopant compound is preferably included in an amount of 0.1 to 3% by weight based on the total weight of the light emitting layer, and the photon efficiency of the first dopant compound in the above weight range may exhibit a high efficiency of 0.90 or more. Also, the first dopant compound is preferably included in a doped form in the host compound. When the first dopant compound is included in less than 0.1% by weight, there may be a problem in that energy transfer to the first dopant compound is not smooth, and when the first dopant compound is included in more than 3% by weight, the host compound has a relative As a result, the rate at which energy is directly transferred to the first dopant compound having poor delayed fluorescence property increases, so that an amount of energy smaller than the amount of energy obtained through the second dopant compound having good delayed fluorescence property is generated, and the first dopant The photon efficiency of the compound may decrease, and thus the efficiency of the light emitting layer may decrease.

As the potential difference between the triplet energy (S ₁ ) and the singlet energy (T ₁ ) of the dopant compound is small, a reverse system transition from triplet energy to singlet energy can easily occur, so delayed fluorescence characteristics can be improved. Specifically, when the potential difference between the singlet energy (S ₁ ^D1 ) and the triplet energy (T ₁ ^D1 ) of the first dopant compound is 0.21 eV or less, and the second dopant compound is a delayed fluorescent material, the singlet energy (S ₁ ^D2 ) When the potential difference between the triplet energy and the triplet energy (T ₁ ^D2 ) is 0.21 eV or less, an inverse system transition can occur actively with only thermal energy at room temperature, so that even without using a heavy metal material commonly used as a conventional phosphor material, like a phosphor material, 100% internal quantum efficiency is available. Therefore, the efficiency of the light emitting layer can be further improved. More preferably, the potential difference between the singlet energy (S ₁ ^D1 ) and the triplet energy (T ₁ ^D1 ) of the first dopant compound is 0.1 eV or less, and the singlet energy (S 1 D2 ) and the triplet energy (S ₁ ^D2 ) of the second dopant compound are 0.1 eV or less. Efficiency of the light emitting layer can be further improved when the potential difference of energy (T ₁ ^D2 ) is 0.1 eV or less.

The first dopant compound is a delayed fluorescent material, preferably having a polycyclic structure including boron, and more specifically may have a structure shown in Formula 1 below.

[Formula 1]

In Formula 1, ring A, ring B, ring C, and ring D are each independently a substituted or unsubstituted aryl ring or heteroaryl ring, and X ¹ , X ² , X ³ and X ⁴ are each independently O; NR or S, wherein R of NR is a substituted or unsubstituted C ₆ -C ₂₀ aryl group, substituted or It may be an unsubstituted C ₂ -C ₂₀ heteroaryl group, a substituted or unsubstituted C ₃ -C ₁₀ cycloalkyl group, or a substituted or unsubstituted C ₁ -C ₁₀ alkyl group. In addition, R ¹ and R ² are each independently hydrogen, heavy hydrogen, C ₁ -C ₆ alkyl group, C ₃ -C ₁₂ cycloalkyl group, C ₆ -C ₁₂ aryl group, C ₂ -C ₁₅ heteroaryl group, diarylamino group (provided that aryl is C ₆ -C ₁₂ aryl), a cyano group, or a halogen.

In the first dopant compound, boron atoms (B) are positioned with an aromatic ring interposed therebetween as shown in Formula 1, and each boron atom is connected to the ring structure, and electrons are symmetrical to the alicyclic carbon hexagonal ring containing the boron atom. In the case of a structure in which atoms with high affinity are located, a high horizontal orientation ratio is observed along with the singlet and triplet energy relationships.

Formula 1 may be more specifically represented by Formula 1-1 below.

[Formula 1-1]

In Formula 1-1, R ₁ to R _{2 ,} R ₄ to R ₇ , and R ₉ to R ₁₀ are each independently hydrogen, deuterium, a nitrile group, a halogen, a substituted or unsubstituted C ₆ -C ₂₀ aryl group, A substituted or unsubstituted C ₂ -C ₂₀ heteroaryl group, a substituted or unsubstituted C ₁₂ -C ₂₀ diarylamino group, a substituted or unsubstituted C ₄ -C ₂₀ diheteroarylamino group, a substituted or unsubstituted C ₂ -C ₂₀ arylheteroarylamino group, substituted or unsubstituted C ₁ -C ₁₀ alkyl group, substituted or unsubstituted C ₃ -C ₁₀ cycloalkyl group, substituted or unsubstituted C ₁ -C ₁₀ alkene group, substituted or unsubstituted C ₁ -C ₁₀ alkane group, substituted or unsubstituted C ₁ -C ₁₀ alkoxy group, substituted or unsubstituted C ₆ -C ₂₀ aryloxy group, substituted or unsubstituted C ₂ -C ₂₀ heteroaryloxy group , A substituted or unsubstituted C ₆ -C ₂₀ arylthio group, a substituted or unsubstituted C ₂ -C ₂₀ heteroarylthio group, or a substituted or unsubstituted C ₁ -C ₁₀ alkyl-substituted silyl group.

In Formula 1-1, R ₃ and R ₈ are each connected to X ₁ and X ₄ to form a ring structure, or each independently hydrogen, deuterium, nitrile group, halogen, substituted or unsubstituted C ₆ -C ₂₀ Aryl group, substituted or unsubstituted C ₂ -C ₂₀ heteroaryl group, substituted or unsubstituted C ₁₂ -C ₂₀ diarylamino group, substituted or unsubstituted C ₄ -C ₂₀ diheteroarylamino group, substituted or unsubstituted A substituted C ₂ -C ₂₀ arylheteroarylamino group, a substituted or unsubstituted C ₁ -C ₁₀ alkyl group, a substituted or unsubstituted C ₃ -C ₁₀ cycloalkyl group, a substituted or unsubstituted C ₁ -C ₁₀ alkene group, A substituted or unsubstituted C ₁ -C ₁₀ alkane group, a substituted or unsubstituted C ₁ -C ₁₀ alkoxy group, a substituted or unsubstituted C ₆ -C ₂₀ aryloxy group, a substituted or unsubstituted C ₂ -C ₂₀ A heteroaryloxy group, a substituted or unsubstituted C ₆ -C ₂₀ arylthio group, a substituted or unsubstituted C ₂ -C ₂₀ heteroarylthio group, or a substituted or unsubstituted C ₁ -C ₁₀ alkyl-substituted silyl group.

A substituted C ₆ -C ₂₀ aryl group, a substituted C _{2 -C 20} heteroaryl group, a substituted C ₁₂ -C ₂₀ diarylamino group, or a substituted C ₄ -C ₂₀ diheteroarylamino group of R 1 to R ₁₀ , substituted C ₂ -C ₂₀ arylheteroarylamino group, substituted C ₁ -C ₁₀ alkyl group, substituted C ₃ -C ₁₀ cycloalkyl group, substituted C ₁ -C ₁₀ alkene group, substituted C ₁ -C ₁₀ alka Popular, substituted C ₁ -C ₁₀ alkoxy group, substituted C ₆ -C ₂₀ aryloxy group, substituted C ₂ -C ₂₀ heteroaryloxy group, substituted C ₆ -C ₂₀ arylthio group, substituted C ₂ At least one of the substituents of the -C ₂₀ heteroarylthio group and the substituted C ₁ -C ₁₀ alkyl-substituted silyl group is a C ₆ -C ₂₀ aryl group, a C ₂ -C ₂₀ heteroaryl group, or a C ₁ -C ₁₀ alkyl group.

R ₁₁ to R ₁₂ in Formula 1-1 correspond to R ¹ and R ² in Formula 1, respectively, and each independently represents hydrogen, deuterium, a C ₁ -C ₆ alkyl group, or a substituted or unsubstituted C ₆ -C ₁₂ aryl group. am.

At least one of the substituents of the substituted C ₆ -C ₂₀ aryl group of R ₁₁ to R ₁₂ is C ₆ -C ₂₀ aryl group, deuterium, nitrile group, halogen, C ₂ -C ₂₀ heteroaryl group, C ₁₂ -C ₂₀ diarylamino group, C ₄ -C ₂₀ diheteroarylamino group, C ₂ -C ₂₀ arylheteroarylamino group, C ₁ -C ₁₀ alkyl group, C ₃ -C ₁₀ cycloalkyl group, C ₁ -C ₁₀ alkene group, C ₁ -C ₁₀ Alkyne group, C ₁ -C ₁₀ Alkoxy group, C ₆ -C ₂₀ Aryloxy group, C ₂ -C ₂₀ Heteroaryloxy group, C ₆ -C ₂₀ Arylthio group, C ₂ -C ₂₀ Heteroaryl group Ogi or C ₁ -C ₁₀ Alkyl substituted silyl group,

X ₁ to X ₄ are each independently O, NR, or S, and R of NR is a substituted or unsubstituted C ₆ -C ₂₀ aryl group, a substituted or unsubstituted C ₂ -C ₂₀ heteroaryl group, or a substituted or an unsubstituted C ₁ -C ₁₀ alkyl group or an adjacent R ₃ or R ₈ connected to form a ring structure, wherein R is a substituted C ₆ -C ₂₀ aryl group, a substituted C ₂ -C ₂₀ heteroaryl group, And at least one of the substituents of the substituted C ₁ -C ₁₀ alkyl group may be substituted with deuterium, F, -O-R', -C( -R ″) ₂ -. And R' and R'' are each independently hydrogen or C ₁ -C ₆ alkyl.

Y ₁ to Y ₂ are each independently hydrogen, heavy hydrogen, a substituted or unsubstituted C ₆ -C ₂₀ aryl group, a substituted or unsubstituted C ₂ -C ₂₀ heteroaryl group, a substituted or unsubstituted C ₁₂ -C ₂₀ Diarylamino group, substituted or unsubstituted C ₄ -C ₂₀ diheteroarylamino group, substituted or unsubstituted C ₂ -C ₂₀ arylheteroarylamino group, substituted or unsubstituted C ₁ -C ₁₀ alkyl group, substituted or unsubstituted A substituted C ₃ -C ₁₀ cycloalkyl group, a substituted or unsubstituted C ₁ -C ₁₀ alkene group, a substituted or unsubstituted C ₁ -C ₁₀ alkane group, a substituted or unsubstituted C ₆ -C ₂₀ aryloxy group, A substituted or unsubstituted C ₂ -C ₂₀ heteroaryloxy group, a substituted or unsubstituted C ₆ -C ₂₀ arylthio group, or a substituted or unsubstituted C ₂ -C ₂₀ heteroarylthio group, wherein Y ₁ to Y ₂ substituted C ₆ -C ₂₀ aryl group, substituted or unsubstituted C ₂ -C ₂₀ heteroaryl group, substituted or unsubstituted C ₁₂ -C ₂₀ diarylamino group, substituted or unsubstituted C ₄ -C ₂₀ Diheteroarylamino group, substituted or unsubstituted C ₂ -C ₂₀ arylheteroarylamino group, substituted or unsubstituted C ₁ -C ₁₀ alkyl group, substituted or unsubstituted C ₃ -C ₁₀ cycloalkyl group, substituted or unsubstituted A C ₁ -C ₁₀ alkene group, a substituted or unsubstituted C ₁ -C ₁₀ alkane group, a substituted or unsubstituted C ₆ -C ₂₀ aryloxy group, a substituted or unsubstituted C ₂ -C ₂₀ heteroaryloxy group, At least one of the substituents of the substituted or unsubstituted C ₆ -C ₂₀ arylthio group or the substituted or unsubstituted C ₂ -C ₂₀ heteroarylthio group is a C ₆ -C ₂₀ aryl group or a C ₂ -C ₂₀ heteroaryl group. , a C ₁ -C ₁₀ alkyl group or a C ₁ -C ₁₀ alkyl-substituted silyl group.

The light-emitting layer for an organic light-emitting device according to an aspect of the present invention can realize high efficiency and color purity by using a delayed fluorescent material as a final light-emitting body together with the energy relationship between the singlet and triplet, and in particular, as shown in Chemical Formula 1 above. When the first dopant compound is used, it is possible to stably emit blue light, so that blue light, which could only be emitted through low-efficiency fluorescence, can be emitted with high efficiency.

The first dopant compound may have, for example, a structure represented by one of Chemical Formulas 2 to 71 below.

The half height width of the first dopant compound is preferably smaller than the half height width of the second dopant compound. The narrower the half width, the higher the color purity, and when the half width of the first dopant compound, which is the final light emitting device, is smaller than the half width of the second dopant compound, the half width of the electroluminescence spectrum of the device is narrow, resulting in improved color purity.

Energy is transferred from the host compound to the first dopant compound or the second dopant compound, and the energy of the second dopant compound is transferred to the first dopant compound by the triplet and singlet energy relationship. In this case, energy utilization efficiency is high when the first dopant compound receives energy generated through the second dopant compound rather than directly receiving energy from the host compound. Therefore, if the process of generating a larger amount of energy and transferring the energy to the first dopant compound by including the second dopant compound at a higher weight percentage becomes the main energy transfer process, the first dopant compound, which is the final light emitting material, emits light. efficiency can be increased. Therefore, it is preferable in terms of energy utilization efficiency that the second dopant compound in the light emitting layer for an organic light emitting device is included in a higher weight % than the first dopant compound.

The second dopant compound serves to receive energy from the host compound and transfer energy to the first dopant compound, and the second dopant compound may include at least one of a delayed fluorescent material and a phosphorescent material having an electron withdrawer-electron acceptor structure. there is. As a specific example, the delayed fluorescent material having an electron withdrawer-electron acceptor structure of the second dopant compound uses a boron compound, triazine, cyano group, sulfone, etc. as a development acceptor, and uses a carbazole derivative, an acridan derivative, etc. as an electron donor. It can be a substance used by dogs. In addition, the phosphorescent material of the second dopant compound is specifically a phosphorescent material of a heavy metal, and as a specific example, may be at least one of Ir, Pt, and Pd, but is not limited to the above example.

The host compound that transfers energy to the second dopant compound may use a host material generally used in the light emitting layer of an organic light emitting device, and specific examples include mCP, mCBP, mCBP-CN, and 2CzPy having a triplet energy of 2.9 eV or more. Host compounds containing carbazole, such as DBFPO and DPEPO, compounds containing phosphine oxide, such as DBFPO and DPEPO, and host materials containing triazine, such as DDBFT and pSiTrz, may be used, but are not limited to the above examples.

In this case, the host compound may contribute to improving device characteristics such as efficiency and lifetime characteristics when two or more different host compounds are used rather than using only one material. For example, when an electron-type host that moves electrons well and a host that moves holes well are used together, holes and electrons meet in a balanced manner in the light emitting layer, and high efficiency and lifespan characteristics can be expected. In addition, when a host forming an exciplex is used, the driving voltage is lowered due to a small energy difference between the light emitting layer and the adjacent layer, and more energy is generated through a reverse field transition process between the host materials. At the same time, excitons are formed widely inside the light emitting layer. As a result, the efficiency and lifetime characteristics of the device can be improved.

An organic light emitting device according to one aspect of the present invention includes the light emitting layer of the present invention, specifically, a first electrode, a second electrode provided to face the first electrode, and between the first electrode and the second electrode. and an organic material layer located therein, and the organic material layer includes the light emitting layer of the present invention. At this time, the organic material layer may form a multi-layered structure, and specifically include at least one layer of an electron injection layer (EIL), an electron transport layer (ETL), a light emitting layer (EML), a hole transport layer (HTL), and a hole injection layer (HIL). can When the organic material layer forms a multilayer structure, the organic light emitting device includes, for example, a cathode, an electron injection layer (EIL), an electron transport layer (ETL), a light emitting layer (EML), a hole transport layer (HTL), and a hole injection layer (HIL). ), and can be stacked in the order of the anode.

The organic light emitting device of the present invention has high color purity and excellent efficiency, and can be applied as a light emitting device of various display devices, for example, it can be applied to display devices such as TVs, smart phones, computers, and automobiles.

In addition, the organic light emitting device of the present invention can be applied to a lighting device due to its high efficiency.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention can be implemented in many different forms and is not limited to the manufacturing examples and examples described herein.

[Preparation Example 1: Synthesis of final light-emitting body dopant material]

Intermediate 1 (150 mg, 0.040 mmol) represented by Formula (a) and Intermediate 2 (369 mg, 0.82 mmol) represented by Formula (b), sodium t-butyloxide (174 mg, 1.81 mmol), Xphos (95 mg, 0.20 mmol) and Pd ₂ (dba) ₃ (18.4 mg, 0.02 mmol) were added to 10 ml of toluene and nitrogen was injected. Thereafter, the mixture was stirred at 120° C. for 6 hours, and cooled to room temperature while adding methylene chloride. Filter the mixture using silica gel and concentrate. Thereafter, hexane is added, stirred for 20 minutes, filtered, and dried. 360 mg (75%) of a white solid was obtained.

[Formula a]

[Formula b]

Intermediate 3 (345 mg, 0.29 mmol) and BBr ₃ (0.11 ml, 1.15 mmol) represented by Formula c were put in dichlorobenzene (8 ml) and stirred at 180° C. for 18 hours in a nitrogen environment. Then, after lowering to room temperature, the mixture was diluted in toluene. Filter through silica gel and concentrate. Then recrystallized using hexane to obtain 110 mg (31%) of a yellow solid of Compound 8 represented by Formula 8 below.

[Formula c]

[Formula 8]

[Experimental Example 1: Evaluation of physical properties of compounds]

The physical properties of Compound 8 prepared according to Preparation Example 1 were evaluated. The measured physical properties were measured as a UV-Vis absorption spectrum and a photoluminescence spectrum at room temperature, and the UV-Vis absorption spectrum was diluted in a toluene solvent at a concentration of 10x ^-5 M using a JASCO V-750. Room temperature photoluminescence spectrum was measured using JASCO-FP 8500 equipment under the same conditions. TRPL (Time-Resolved Photoluminescence) was measured by diluting at a concentration of 10x ^-4 M in dichloromethane solvent using Hamamatsu C11367 equipment. Table 1 shows the measurement results.

division Maximum absorption wavelength (nm) Maximum emission wavelength / full width at half maximum (nm) Singlet-triplet energy (eV) Delayed fluorescence exciton lifetime (us) horizontal orientation ratio compound 8 458 467 / 14 0.05 1.90 0.92

[Experimental Example 2: Evaluation of Physical Properties of Organic Light-Emitting Device]

The ITO glass substrate was cut into 50mm x 50mm x 0.7mm size, washed with acetone, isopropyl alcohol, and distilled water for 10 minutes each, irradiated with ultraviolet rays for 10 minutes, exposed to ozone, and cleaned, and then placed in a vacuum deposition device. The ITO glass substrate was mounted. On the ITO glass substrate, HATCN (7 nm) / TAPC (50 nm) / DCDPA (10 nm) / DBFPO host compound: 30% by weight of the second dopant compound (D2): 1% by weight of the first dopant compound (D1) (25 nm) / DBFPO (5 nm) / TPBi (25 nm) / LiF (1.5 nm) / Al (100 nm) were laminated in this order to prepare an organic light emitting device. Structures of the first dopant compound (Compound 1) and the second dopant compound (Compound 2) used in Comparative Examples 1 to 3 and Examples 1 to 4 are shown in Table 2 below, and Comparative Examples 1 to 3 and Example 1 The physical properties of the first dopant compound used in 4 to 4 are shown in Table 3, the energy transfer rate comparison of the dopant compounds is shown in Table 4, and the device measurement results according to the change of the first dopant compound and the second dopant compound are shown in Table 3. 5 and Figures 2 to 6.

division maximum absorption
Wavelength (nm) Maximum emission wavelength / full width at half maximum (nm) singlet -triplet
Energy (eV) Delayed fluorescence exciton lifetime (us) horizontal orientation ratio BD-01 429 452/30 1.40 - 0.70 v-DABNA 458 467 / 14 0.05 2.33 0.90 compound 8 458 467 / 14 0.05 1.90 0.92 BD-02 438 452 / 21 0.17 13.8 0.86

division k _r (10 ⁷ s ^-1 ) k _ISC (10 ⁷ s ^-1 ) kFRET _{_} (10 ⁷ s ^-1 ) TD-01 3.34 3.24 TD-01 BD-01 - - 5.56 TD-02 1.13 1.01 TD-02 v-DABNA - - 7.76 compound 8 - - 7.77 TD-03 0.71 3.46 TD-03 BD-01 - - 5.36 BD-02 - - 6.76 TD-04 3.70 1.30 TD-04 BD-02 0.65 PD-01 0.55 PD-01 v-DABNA - - 6.89

division compound Max EQE (%) Full width at half maximum (nm) Maximum electroluminescence wavelength (nm) horizontal orientation ratio Comparative Example 1 TD-01 18.6 67 467 0.80 TD-01: BD-01 11.3 43 458 0.70 Comparative Example 2 TD-03 27.3 68 476 0.78 TD-03: BD-01 19.0 44 458 0.70 Comparative Example 3 TD-04 22.9 69 491 0.80 TD-04: BD-02 17.1 77 491 0.82 Example 1 PD-01 15.3 46 457 0.72 PD-01: v-DABNA 24.9 20 473 0.90 Example 2 TD-02 32.8 60 474 0.82 TD-02: v-DABNA 39.8 19 474 0.90 Example 3 TD-02 32.8 60 474 0.82 TD-02: compound 8 40.7 19 474 0.92 Example 4 TD-03 27.3 68 476 0.78 TD-03: BD-02 36.8 29 458 0.85

In Table 5, in Comparative Examples 1 to 3 and Examples 1 to 4, the physical properties using only the second dopant compound are shown in the upper row, and the lower row shows the first dopant compound and the second dopant compound in the above ratio (second dopant compound). compound: 30% by weight, first dopant compound: 1% by weight).

Through Comparative Example 1 and Comparative Example 2, when the ultra-fluorescent device was manufactured using BD-01, a pyrene-based fluorescent dopant, color characteristics were improved, but due to low horizontal orientation ratio and large singlet-triplet energy difference The maximum efficiency did not exceed that of TADF.

On the other hand, in the case of Example 1 using v-DABNA having a higher horizontal orientation ratio than PD-02 and having delayed fluorescence, it can be seen that, unlike Comparative Example 1, higher efficiency than conventional phosphorescence.

In the case of Example 2 using v-DABNA having a higher horizontal orientation ratio than TD-02 and having delayed fluorescence, it can be seen that, unlike Comparative Example 1, higher efficiency than conventional TADF is obtained.

In the case of Example 3 using Compound 8 with increased horizontal orientation ratio, it can be seen that the efficiency is higher than that of Example 2.

Referring to Figure 3 and Table 5, in the case of Comparative Example 4, in which the Foster energy transfer rate from TD-04 to BD-02 is slower than the light emission rate or interstitial transfer rate of TD-04, unlike Example 4, the energy transfer is not good it can be seen that it does not

In the case of Example 4 using BD-02 having a higher horizontal orientation ratio than TD-03 and having a delayed fluorescence characteristic, it can be seen that, unlike Comparative Example 2, higher efficiency than conventional TADF is obtained.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible without departing from the technical spirit of the present invention described in the claims. It will be obvious to those skilled in the art.

Claims (20)

a first dopant compound having a singlet energy of S ₁ ^D1 and a triplet energy of T ₁ ^D1 ;
a second dopant compound having a singlet energy of S ₁ ^D2 and a triplet energy of T ₁ ^D2 ; and
A host compound having a singlet energy S ₁ ^HOST and a triplet energy T ₁ ^HOST ;
The singlet energy is S ₁ ^HOST > S ₁ ^D2 > S ₁ ^D1 ;
The triplet energy is T ₁ ^D2 > T ₁ ^D1 and T ₁ ^HOST > T ₁ ^D1 ,
The first dopant compound is a delayed fluorescent material containing boron and having a multi-resonance structure,
The second dopant compound is a delayed fluorescent material or a phosphorescent material, a light emitting layer for an organic light emitting device.
According to claim 1,
The second dopant compound is a phosphorescent material,
A light emitting layer for an organic light emitting device, characterized in that a Förster energy transfer rate from the second dopant compound to the first dopant compound is faster than the light emitting transfer rate of the second dopant compound.
According to claim 1,
The second dopant compound is a delayed fluorescent material,
A light emitting layer for an organic light emitting device, characterized in that the Förster energy transfer rate from the second dopant compound to the first dopant compound is faster than the luminescence transfer rate to system transition rate of the second dopant compound.
According to claim 1,
The Förster energy transfer rate from the second dopant compound to the first dopant compound is 5 x10 ⁷ s ^-1 or more, characterized in that, the light emitting layer for an organic light emitting device.
According to claim 1,
Characterized in that the horizontal orientation ratio of the first dopant compound is higher than the horizontal orientation ratio of the second dopant compound, a light emitting layer for an organic light emitting device.
According to claim 1,
A light emitting layer for an organic light emitting device, characterized in that it comprises 0.1 to 3% by weight of the first dopant compound.
According to claim 1,
The potential difference between S ₁ ^D1 and T ₁ ^D1 is 0.21 eV or less,
The second dopant compound is a delayed fluorescent material,
The potential difference between S ₁ ^D2 and T ₁ ^D2 is 0.21 eV, a light emitting layer for an organic light emitting device.
According to claim 1,
The light emitting layer for an organic light emitting device, characterized in that the first dopant compound comprises a structure represented by the following formula (1):
[Formula 1]

In Formula 1,
A ring, B ring, C ring and D ring are each independently a substituted or unsubstituted aryl ring or heteroaryl ring,
X ¹ , X ² , X ³ and X ⁴ are each independently O, NR or S;
R is a substituted or unsubstituted C ₆ -C ₂₀ aryl group, substituted or unsubstituted C ₂ -C, bonded or unbonded to at least one of A, B, C and D rings by a single bond; ₂₀ A heteroaryl group, a substituted or unsubstituted C ₃ -C ₁₀ cycloalkyl group, a substituted or unsubstituted C ₁ -C ₁₀ alkyl group,
R ¹ and R ² are each independently hydrogen, heavy hydrogen, a C ₁ -C ₆ alkyl group, a C ₃ -C ₁₂ cycloalkyl group, a C ₆ -C ₁₂ aryl group, a C ₂ -C ₁₅ heteroaryl group, a diarylamino group ( provided that aryl is a C ₆ -C ₁₂ aryl), a cyano group, or a halogen.
According to claim 8,
The first dopant compound is a light emitting layer for an organic light emitting device, characterized in that for emitting blue light.
According to claim 1,
The first dopant compound is a light emitting layer for an organic light emitting device, characterized in that the structure represented by one of the following formulas 2 to 71:

According to claim 1,
The half-width of the first dopant compound is narrower than the half-width of the second dopant compound, a light emitting layer for an organic light emitting device.
According to claim 1,
The light emitting layer for an organic light emitting device, characterized in that the second dopant compound is included in a higher weight % than the first dopant compound.
According to claim 1,
The second dopant compound is a light emitting layer for an organic light emitting device, characterized in that it comprises a delayed fluorescent material having an electron withdrawer-electron acceptor structure.
According to claim 1,
The second dopant compound is a light emitting layer for an organic light emitting device, characterized in that it comprises at least one phosphorescent material selected from Ir, Pt and Pd.
According to claim 1,
The host compound is characterized in that it comprises one or more of mCP, mCBP, mCBP-CN, 2CzPy, DBFPO, DPEPO, DDBFT and pSiTrz, the light emitting layer for an organic light emitting device.
According to claim 15,
The host compound is a light emitting layer for an organic light emitting device, characterized in that it comprises two or more of the above materials.
a first electrode;
a second electrode provided to face the first electrode; and
Including; organic material layer located between the first electrode and the second electrode,
The organic material layer comprises a light emitting layer for an organic light emitting device according to any one of claims 1 to 16, an organic light emitting device.
According to claim 17,
The organic material layer is an organic light emitting device, characterized in that it comprises at least one layer of an electron injection layer (EIL), an electron transport layer (ETL), a light emitting layer (EML), a hole transport layer (HTL), and a hole injection layer (HIL).
A display device comprising the organic light emitting device of claim 17 .
A lighting device comprising the organic light emitting diode of claim 17 .

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