KR20170118113A - Phosphorescent compound, manufacturing method and organic light emitting diode device - Google Patents

Abstract

The present invention relates to a phosphorescent compound and its structural formula is as follows. The triplet energy of the phosphorescent compound of the present invention is 2.80 or more and is used as a phosphorescent host, and the triplet energy is higher than the triplet energy of the dopant of 2.7ev to obtain a high efficiency phosphorescent device without energy reversal. Since the blue light phosphorescent compound is used as a host of the light emitting layer of the organic light emitting diode, energy transfer in the light emitting layer can be promoted and the efficiency of blue light emission of the organic light emitting diode can be improved. It improves the life span.

Description

Phosphorescent compound, manufacturing method and organic light emitting diode device

The present invention relates to a phosphorescent compound and an organic light emitting diode (OLED) device. More particularly, the present invention relates to a phosphorescent compound having a high luminous efficiency due to high triplet energy and a wide band gap, And an OLED device using the phosphorescent compound.

In recent years, extensive research and development of organic electroluminescent devices have been made. Such a light emitting device basically has a structure in which a layer containing a light emitting material is inserted between a pair of electrodes, and a voltage is applied to the device to emit light from the light emitting material.

Since such a light emitting device is a self-luminous device, it has a higher pixel visibility than a liquid crystal monitor and does not require a backlight, which is considered to be suitable for a flat display device. The light-emitting element is also thin and lightweight and has a considerable competitive advantage. Significantly faster response rates are also a feature of these devices.

In addition, since these devices can be manufactured in a thin film form and can be used to emit plane light, it is easy to form a large-sized device. This is a characteristic that can not be realized by a point light source such as an incandescent lamp and LED or a light source represented by a fluorescent lamp. Therefore, the light emitting device has a great potential for application as a flat light source of an illumination.

The excited state formed through the organic compound can be mono or triple. In a singlet excited state (S *) it is called fluorescence, in triplet excited state (T *) it is called phosphorescence. In addition, it is known that the generation ratio in the light emitting element is S *: T * = 1: 3. When converting the energy of the singlet excited state to the light emitting compound, the singlet excited state emission is observed at room temperature, but the triplet excited state emission is not observed. Therefore, the internal quantum efficiency of a light emitting device using a fluorescent compound has a theoretical 25% limit based on the S * and T * ratio of 1: 3. Organic electric field is one of the materials attracted attention recently, and it is an organic electroluminescent material with high luminous efficiency and brightness. This allows the theoretical quantum efficiency to reach up to 100% by transiting from the room temperature to the originally hindered triplet state by attracting heavy metal atoms, which is four times that of a single fluorescent material (1, CaO Y., Parker ID, Heeger J., Nature, 1999, 397: 414-417.2, Wohlgenann M., et al., Nature, 2001, 409: 494-497). Most of the heavy metal atoms commonly used for organic materials are minerals. Among them, iridium is the most widely used and the research data are the most detailed. This is because the metal iridium complex has a high efficiency and emits relatively strong phosphorescence at room temperature and adjusts the ligand structure to control the emission wavelength so that the color of the electroluminescent element covers the entire visible light region. Therefore, designing and studying the synthesis of new metal iridium complexes with high efficiency is crucial to the development of phosphorescent materials.

However, the dopant is limited to the host-dopant-free luminescent layer because the efficiency is rapidly reduced due to the extinction phenomenon. Therefore, it is necessary to form a light emitting material layer through a host having higher thermal stability and triplet energy than a dopant.

In the case of an OLED device including a phosphorescent compound, holes injected from the anode and electrons injected from the cathode are encountered at the host point of the emissive material layer. The single-termed excitons of the host undergo energy transfer to the single or triplet of dopants, and the triplet excitons injected by the host cause energy transfer to the triplet of dopants. Since the excitons transferred to a single term of the dopant are again transferred to the triplet of the dopant, the excitons of the triplet energy level of the dopant are transited to the ground state, and the light emitting layer emits light.

For the efficient energy transfer of the dopant, the triplet energy of the host must be greater than the triplet energy of the dopant. When the triplet energy level of the host is smaller than the triplet energy of the dopant, the energy reversal phenomenon occurs from the dopant to the host and the luminous efficiency is lowered.

CBP widely used for the host has a triplet energy level of 2.6 eV and a maximum energy level and a lowest energy level of about -6.3 eV and -2.8 eV, respectively. Therefore, when the blue light dopant FCNIr having the triplet energy level of 2.8 eV, the highest energy level of -5.8 eV and the lowest energy level of -3.0 eV is used, the energy reversal phenomenon may occur due to energy reversal from the dopant to the host. Particularly, the decrease in the luminous efficiency is more conspicuous at low temperatures.

It is an object of the present invention to provide a phosphorescent compound having a high triplet energy and a wide band gap.

Still another object of the present invention is to provide an OLED having improved luminous efficiency.

The structure of the phosphorescent compound of the present invention is as follows.

Wherein only one of A, B and C is a heteroatom N and the remainder is a C atom;

1, 2, 3 and 4 are heteroatoms N and the remainder are C atoms;

Ar is a C6-C30 substituted or unsubstituted aryl, heteroaryl or polycyclic aromatic hydrocarbon.

5, 6, 7 and 8 show the positions where the C atoms are bonded on the I carbazoline ring and the II carbazole ring.

The structural formula of Ar is as follows.

Preferably, Ar is phenyl, naphthyl, phenyl substituted phenyl or naphthyl, heteroaryl or polycyclic aromatic hydrocarbons.

Preferably, the I carbazoline ring and the II carbazole ring are linked to the 6 or 7 position.

Preferably, it is as follows.

Wherein Ar is phenyl.

Preferably, A or B is an N atom.

In the method of synthesizing the above phosphorescent compound, the I carbazoline ring and the II carbazole ring are respectively made into a bromide, boric acid or borate ester, and are connected together through an SUZUKI coupling reaction.

The I-carbazoline ring bromide is prepared by reacting I carbazolin with pyridinium bromide to produce N-atom-substituted carbazoline and then again via NBS bromide.

The organic light emitting diode device includes a first electrode; A second electrode relative to the first electrode; And a light-emitting layer between the first electrode and the second electrode, wherein the light-emitting layer includes the phosphorescent compound.

The light emitting layer material includes a host and a dopant, and the phosphorescent compound is a host material.

The phosphorescent compound is used as a blue light phosphorescent host material.

The three positions A, B and C in the general formula of the compound of the present invention are each composed of 2-pyridine, 3-pyridine and 4-pyridine structures at positions where nitrogen atoms are present.

The 1, 2, 3 and 4 positions of the I carbazole ring are nitrogen atoms and each constitute the four isomers of carbazoles.

The positions 5, 6, 7 and 8 of the II carbazole ring are the positions where the two rings are bonded.

In the present invention, the triplet energy level of the phosphorescent compound is 2.80 or more, which is used as a phosphorescent host. Since the triplet energy level is larger than the triplet energy level 2.7ev of the dopant material, no energy reversal occurs and a high efficiency phosphorescent device is obtained .

Since the blue light phosphorescent compound is used as a host of the light emitting layer of the organic light emitting diode, energy transfer in the light emitting layer can be promoted and the efficiency of blue light emission of the organic light emitting diode can be improved. It improves the life span.

1 is an NMR diagram of a D structure in Example 1;
Figure 2 is a local enlargement of Figure 1;
3 is an NMR diagram of Compound 1 in Example 1;
4 is an NMR diagram of Structure A in Example 3; And
5 is an NMR diagram of Structure A in Example 4. Fig.

Hereinafter, the objects, technical solutions and effects of the present invention will be described more clearly and completely. The following examples are for the purpose of interpreting the present invention and are not to be construed as limiting the scope of the present invention. The following compounds A, B, and E were synthesized based on literature data (Chem. Commun., 2013, 49, 5948-5950).

Example 1: Preparation of first host

Synthesis of intermediate C:

0.1 mol A, 0.2 mol B, 0.2 mol sodium tert-butoxide and 0.002 mol palladium acetate were added to a 2 L four-necked flask, and 1 L toluene was added to a 2 L four necked flask, stirred and charged with nitrogen for 30 minutes 1ML (50% toluene solution) Tri-tert-butylphosphine was added and the mixture was heated to reflux for 4 hours, followed by cooling and filtration to obtain a mother liquor. The mother liquor was concentrated to give a light yellow solid. Mass spectrum (ESI, 245.3)

Synthesis of intermediate D:

0.1 mol C was dissolved in 300 mL DMF, completely dissolved at 50 ° C and 0.1 mol NBS was added. Gradually an off-white solid precipitated. After the NBS spill was completed, it was stirred overnight, cooled and filtered to give an off-white solid. The NMR diagram was checked and locally expanded in FIG.

Synthesis of Compound 1:

0.1 mol of D and 0.1 mol of E were added to a 2 L four-necked flask, and 400 mL of toluene, 200 mL of ethanol and 200 mL of water were added and stirred. After addition of 0.2 mol of potassium carbonate by dividing the difference, 0.5 g of tri-tert-butylphosphine (50% toluene solution) was added, and the mixture was refluxed overnight. Cooling and filtration gave a pale yellow solid and mass spectrum 486.5 (MODI-TOF) was detected.

(HNMR (CDCl 3, 8.73, 1 H, 8.45, 3H, 8.35-8.40, 3H, 7.99, 1 H, 7.90, 1 H 7.75-7.78, 1 H, 7.62-7.64, 4H, 7.4-7.5, 4H, 2 See also.

Example 2: Fabrication of the second host

Synthesis of Compound 2:

0.1 mol D and 0.1 mol E2 were added to a 1 L four-necked flask, and 400 ML of toluene, 200 ML of ethanol and 200 ML of water were added and stirred. After the addition of 0.2 mol of potassium carbonate by dividing the time, nitrogen was charged for 30 minutes, palladium acetate 0.5G, tri-tert-butylphosphine 1ML was added and refluxed overnight. Cooling and filtration gave a pale yellow solid and mass spectrum 486.5 (MODI-TOF) was detected.

NMR

H NMR (CDCl 3, 8.74, 1 H, 8.46, 3H, 8.36-8.41, 3H, 7.98, 1H, 7.91, 1H, 7.77-7.79, 1H, 7.65-7.67, 4H, 7.5-7.6, 4H,

Example 3: Synthesis of the third host

carbazole is replaced by the [alpha] -carbazoline of compound I to give compound 3. [

Here, the NMR diagram of A3 is as shown in Fig.

NMR

H NMR (CDCl3, 8.77, 1H, 8.48,3H, 8.38-8.42, 3H, 7.99, 1H, 7.92, 1H, 7.75-7.78,1H, 7.63-7.67, 4H, 7.4-7.5,

Example 4

Compound 4 was easily obtained according to the synthetic steps of Compounds 1 and 2.

Here, the NMR diagram of A4 is as shown in Fig.

NMR

H NMR (CDCl3, 8.71, 8.1, 8.42,3H, 8.35-8.41, 3H, 7.99, 1H, 7.92, 1H, 7.71-7.74,1H, 7.62-7.64,4H, 7.4-7.5,4H, 7.29,3H)

Example 5

The UV absorption spectra and the optical luminescence spectra of the first to fourth host materials prepared according to the above-described synthesis examples of the present invention and the comparative materials represented by the following formulas were measured at a low temperature (for example, 77K) The results are shown in the following table.

              Comparative Example

Maximum wavelength (nm) of UV absorption spectrum Maximum wavelength (nm) of PL spectrum Band gap LUMO energy (eV) HOMO energy (eV) Triplet energy (eV) Comparative Example 365 425 3.40 -2.43 -5.83 2.92 The first host 358 443 3.47 -2.18 -5.65 2.80 Second host 362 424 3.43 -2.25 -5.68 2.93 Third host 355 424 3.50 -2.15 -5.65 2.93 Fourth host 359 424 3.46 -2.20 -5.66 2.93

As can be seen in Table 1, since the triplet energies from Host 2 to Host 4 are all higher than 2.92 eV, they can meet the criteria of a blue light phosphorescent host.

Hereinafter, a performance test of an organic light emitting diode using a blue light phosphorescent compound formed by the first and second host materials and a material of a comparative example as a blue light host will be described.

Example 6

The ITO substrate was patterned and the light emitting area was made 3 mm x 3 mm and then cleaned. The ITO substrate was placed in a vacuum chamber and the bottom pressure was made to 1 × 10 ^-6 Torr. HATCN having a thickness of about 50 angstroms was used for the hole injection layer, NPD having a thickness of about 550 angstroms was used for the hole transport layer, and a thickness of about 100 angstroms TAPC was used in the hole injection layer, and a first host material with a thickness of about 300 angstroms and FNCIr with a dopant concentration of about 15% were used in the light emitting layer. Then, TmPyPb having a thickness of 400 angstroms was used for the electron transporting layer, and LiF having a thickness of about 5 angstroms was used for the electron injecting layer to form an Al layer anode having a thickness of 1100 angstroms. Thereafter, a packaging process was performed using a UV curable sealing agent and a moisture absorbent to form a light emitting diode.

Example 7

Except that an organic light emitting diode was manufactured using the same manufacturing process as described above and a second host was used as a light emitting host.

Comparative Example

An organic light emitting diode was prepared by the same process as in Production Example 1, except that a comparative host was used as a light emitting host.

Voltage
(volt) Launch efficiency Quantum efficiency
(%) Color coordinates Service life (T50, 700nit) Cd / A Im / W CIE_x CIE_y Comparative Example 5.3 13.20 7.85 7.77 0.154 0.274 4 Example 1 7.5 16.98 7.14 10.48 0.154 0.253 108 Example 2 7.3 16.94 7.25 10.43 0.154 0.255 218

As shown in Table 2, it can be seen that the organic light emitting diodes manufactured in Examples 1 and 2 have improved luminous efficiency, quantum efficiency and service life when displaying the same color coordinates as those of the comparative examples. In particular, the service life of organic light emitting diodes is greatly improved.

As described above, the present invention relates to a blue phosphorescent compound having a high triplet energy, wherein the blue phosphorescent compound is used as a host of a light emitting layer of an organic light emitting diode to promote energy transfer of the light emitting layer, And improved service life.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. It will be understood. More specifically, it is possible to proceed with various modifications and improvements in terms of components and / or arrangements in combination with the drawings disclosed in the present invention and the subject matter of the claims. It will be appreciated by those skilled in the art that substitutions and adaptations other than changes and improvements in constructional aspects and / or aspects of the arrangements may be readily apparent to those skilled in the art.

Claims (10)

The structure is as follows,

Wherein only one of A, B and C is a heteroatom N and the remainder is a C atom;
1, 2, 3 and 4 are heteroatoms N and the remainder are C atoms;
Ar is a C6-C30 substituted or unsubstituted aryl, heteroaryl or polycyclic aromatic hydrocarbon,
5, 6, 7 and 8 represent positions where the C atom is conjugated on the I carbazoline ring and the II carbazole ring. The method according to claim 1,
The structural formula of Ar

Lt; / RTI > 3. The method of claim 2,
Ar is phenyl, naphthyl, phenyl substituted phenyl or naphthyl, heteroaryl or polycyclic aromatic hydrocarbon. The method of claim 3,
Wherein the I carbazolidine ring and the II carbazole ring are linked to the 6 or 7 position. 5. The method of claim 4,
Structural formula

ego;
Wherein Ar is phenyl. The method for synthesizing the phosphorescent compound according to any one of claims 1 to 5, wherein the I carbazoline ring and the II carbazole ring are each made into a bromide, boric acid or borate ester and are connected together through an SUZUKI coupling reaction. The method according to claim 6,
Wherein said I carbazoline ring bromide is produced by reacting I carbazoline with pyridinium bromide to produce an N-atom substituted carbazoline and then again through NBS bromide. .

A first electrode; A second electrode relative to the first electrode; And a light emitting layer between the first electrode and the second electrode, wherein the light emitting layer comprises the phosphorescent compound according to any one of claims 1 to 5. 9. The method of claim 8,
Wherein the light emitting layer material comprises a host and a dopant, and the phosphorescent compound is a host material. 9. The method of claim 8,
Wherein the phosphorescent compound is used as a blue light phosphorescent host material.

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