JP6607597B2 - Novel organic lithium complex compound, electron injection material comprising the same, and organic EL device using the same - Google Patents

Description

  The present invention relates to a novel organolithium complex compound, an electron injection material comprising the same, and an organic EL device using the same.

  One means for improving the practicality of organic EL devices is to reduce the drive voltage. On the other hand, the energy barrier from the electrode of the organic EL device to the organic layer leads to higher voltage and lower efficiency. As a technique for lowering the energy barrier, there is an improvement of an electron injection material used for the electron injection layer. Specifically, an ultrathin layer of lithium (Φ = 2.9 eV) having a low work function or lithium fluoride (LiF) having a thickness of 1 nm or less is inserted at the interface between an organic film such as an electron transport layer and an aluminum cathode. As a result, the driving voltage of the element has been reduced and the luminous efficiency has been improved by 1.4 times compared to the conventional organic EL device. Further, it has been found that insertion of metallic lithium or a lithium compound at the interface between the light emitting layer (Alq3) and the aluminum cathode improves the electron injection property based on a mechanism called self-doping.

  On the other hand, metallic lithium is difficult to handle, and lithium fluoride has a very high boiling point of 1680 ° C., which makes it expensive to manufacture devices. Since lithium fluoride is an insulator, it is an extremely thin film of about 0.5 nm. Otherwise, there is a problem that the film does not function and the film thickness control is severe. In addition, since lithium fluoride has poor solubility in a solvent, there is a problem that it cannot be used for a coating type organic EL device.

Devices in which Liq, Naq, Liacac, and Lidpm were inserted as the electron injection material at the interface between the organic layer and the metal cathode were reported (Non-Patent Documents 1 to 3). These alkali metal complexes are materials having both stability and conductivity in the atmosphere. Among these, when Liq and Naq are inserted between the light emitting layer (Alq3) and the aluminum cathode, the central metal ions (Li ⁺ , Na ⁺ ) are reduced by the thermally activated aluminum, and radicals are generated. It is believed to form anions and facilitate electron injection from the aluminum cathode.

As an alkali metal complex having a ligand similar in structure to Liq, LiMeq in which a methyl group is introduced into Liq has been developed, and an organic EL element using Liq and LiMeq as an electron injection layer has been reported (non-patent document). Reference 4).

In addition, ITO (Indium Tin Oxide) / NPB (N, N′-diphenyl- (1,1′-biphenyl) -4,4′-diamine) / Alq3 (in which LiOXD having a thickness of 2 nm is introduced as the electron injection layer) An organic EL element composed of tris (8-quinolinolato) aluminum) / LiOXD / Al has also been reported (Non-patent Document 5).

Thereafter, LiPP, Li2BPP, and LiIQP having a structure in which the π conjugate length has been extended from Liq that has already been reported have been developed, and it has been reported that the electron transport property of an organic EL device incorporating these has been improved. In particular, in LiPP, when the film thickness was changed from 3 nm to 40 nm, the driving voltage increased by 3 V or more, whereas in Li2BPP and LiIQP, even a thick film showed low voltage driving, and in addition, the π conjugate was wide, so it was high. It has been reported that the electron transport property is exhibited and the driving voltage is reduced as compared with LiPP (Non-Patent Document 6).

Among these, a high-efficiency green phosphorescent device using Li2BPP has been developed, and Liq, Li2BPP is used for the electron injection layer, B4PyPPM, B4PyMPM is used for the electron transport layer, and Ir (ppy) ₃ (Tris (2-phenylpyridina) G) Driving voltage is greatly reduced in a green phosphor element produced by using CBP (4,4′-bis (carbazol-9-yl) biphenyl) doped with iridium (III)) as a light emitting layer. (Non-Patent Document 7).

J. Endo, T. Matsumoto and J. Kido, Ext. Abstr. (59th Autumn Meet. 1998); Japan Society of Applied Physics, p. 1086 J. Endo, T. Matsumoto and J. Kido: Ext. Abstr. 9th Int. Workshop on Inorganic & Organic Electroluminescence (1998) p. 57 J. Endo, T. Matsumoto and J. Kido, Jpn. J. Appl. Phys. 41, L800 (2002) C. Schmitz, H-W Schmidt and M. Thelakkat, Chem. Mater., 12, 3012-3019 (2000) F. Liang, J. Chen, L. Wang, D. Ma, X. Jing and F. Wang, J. Mater. Chem., 13,2922-2926 (2003) Y.-J.Pu, M. Miyamoto, K. Nakayama, T. Oyama, M. Yokoyama and J. Kido, Org. Electron., 10, 228 (2009) H. Sasabe, H. Nakanishi, Y. Watanabe, S. Yano, M. Hirasawa, Y.-J. Pu and J. Kido, Adv. Funct. Mater., 10.1002 (2013)

  An object of the present invention is to develop a new electron injection material and realize further low voltage driving, and to provide a novel organic lithium complex compound, an electron injection material using the same, and an organic EL device And

上記式（１）中、Ａｒはトリアジニル基、３−ピリジル基又は４−ピリジル基を表す。
本発明の電子注入材料は、上記有機リチウム錯体化合物からなることを特徴とする。
本発明の有機ＥＬ素子は、上記有機リチウム錯体化合物からなることを特徴とする。
The organolithium complex compound of the present invention is represented by the following formula (1).

In said formula (1), Ar represents a triazinyl group, 3-pyridyl group, or 4-pyridyl group .
The electron injection material of the present invention is characterized by comprising the above organolithium complex compound.
The organic EL device of the present invention is characterized by comprising the above organic lithium complex compound.

ADVANTAGE OF THE INVENTION According to this invention, the organolithium complex compound suitable as an electron injection material of an organic EL element is compoundable with a high yield. Specifically, the bromo compound 2BrPP was synthesized in a high yield by Suzuki-Miyaura coupling of 2,6-dibromopyridine and 2-hydroxyphenylboronic acid, and the corresponding pyridine boronic acid ester with the bromo compound 2BrPP 3BPP and 4BPP can be synthesized in high yield by Suzuki-Miyaura coupling, and Li3BPP and Li4BPP can be synthesized almost quantitatively by reaction of the 3BPP and 4BPP with lithium hydroxide.
When the organolithium complex compound of the present invention is inserted as an electron injection layer between the electron transport layer and the cathode metal by about several nanometers, the voltage of the device can be greatly reduced. In particular, Li3BPP and Li4BPP have high electron-withdrawing 3-pyridyl and 4-pyridyl groups, so that both HOMO and LUMO can be deepened, and the electron injection barrier can be reduced.
Furthermore, the organolithium complex compound of the present invention has high thermal stability and sublimation properties, has a low deposition temperature of about 300 ° C., and functions as an element even with a relatively thick film. Moreover, since it is stable in the air, it is easy to handle.
Since the organolithium complex compound of the present invention has a ligand composed of an organic compound, the organolithium complex compound is soluble in a general organic solvent and can be coated and formed by a solution method.

FIG. 1 shows a ¹ HNMR spectrum of Li3BPP. FIG. 2 shows a ¹ HNMR spectrum of Li4BPP. FIG. 3 is a diagram showing UV-vis spectra of Li2BPP, Li3BPP, and Li4BPP. FIG. 4 is a diagram showing PL spectra of Li2BPP, Li3BPP, and Li4BPP. FIG. 5 is a diagram showing the PYS measurement result of Li3BPP. FIG. 6 is a diagram showing the PYS measurement result of Li4BPP. FIG. 7 is a diagram showing an element structure. FIG. 8 is a diagram showing an EL spectrum of a coating type yellow-green element. FIG. 9A is a diagram illustrating a relationship between current density and voltage characteristics (linear), and FIG. 9B is a diagram illustrating a relationship between current density and voltage characteristics (logarithm). FIG. 10 is a diagram illustrating the relationship between luminance and voltage characteristics. FIG. 11 is a diagram illustrating the relationship between power efficiency and luminance characteristics. FIG. 12 is a diagram illustrating a relationship between current efficiency and luminance characteristics. FIG. 13 is a diagram illustrating the relationship between external quantum efficiency and luminance characteristics. FIG. 14 is a diagram showing an EL spectrum of an element using a polymer binder. FIG. 15A is a diagram illustrating a relationship between current density and voltage characteristics (linear), and FIG. 15B is a diagram illustrating a relationship between current density and voltage characteristics (logarithm). FIG. 16 is a diagram illustrating the relationship between luminance and voltage characteristics. FIG. 17 is a diagram illustrating the relationship between power efficiency and luminance characteristics. FIG. 18 is a diagram illustrating a relationship between current efficiency and luminance characteristics. FIG. 19 is a diagram illustrating the relationship between external quantum efficiency and luminance characteristics.

上記式（１）中、Ａｒは芳香族炭化水素基を表す。 Hereinafter, the present invention will be described in detail.
[Organic lithium complex compound]
The organolithium complex compound of the present invention is represented by the following general formula (1):

In the above formula (1), Ar represents an aromatic hydrocarbon group.

Examples of the aromatic hydrocarbon group include phenyl group, pyrimidine (pyrimidinyl group), triazine (triazinyl group), pyridine (3-pyridyl group, 4-pyridyl group) and the like. Among these, pyrimidine, triazine, 3-pyridyl group and 4-pyridyl group are preferable, and 3-pyridyl group and 4-pyridyl group are more preferable from the viewpoint of synthetic chemistry and electronic properties.
Specifically, the compound represented by the general formula (1) is preferably a compound having the following structural formula.

The compound represented by the general formula (1) can be produced by various known methods. For example, Li3BPP can be synthesized using the Suzuki-Miyaura coupling reaction as shown below.

That is, 2,6-dibromopyridine and 2-hydroxyphenylboronic acid are placed in a three-necked flask and stirred with a base such as potassium carbonate in the presence of a Pd (0) catalyst to obtain 2BrPP at a yield of 80%. . Next, the obtained 2BrPP and 3-pyridineboronic acid ester are put into a three-necked flask and heated and refluxed with a base such as tripotassium phosphate in the presence of a Pd (0) catalyst and a ligand. 3BPP is obtained with a yield of 96%. Li3BPP is obtained almost quantitatively by reacting the obtained 3BPP with lithium hydroxide.
However, the compound represented by General formula (1) of this invention is not restricted to the said method, It can manufacture by combining a well-known various method.

The organolithium complex compound of the present invention obtained as described above has a sufficiently high melting point (T _m ) and decomposition point (T _d5 ), and is excellent in thermal stability. In particular, L3BPP and L4BPP have higher melting points (T _m ) and decomposition points (T _d5 ) than L2BPP, despite having the same molecular weight as L2BPP described in the section of the prior art. This is probably because nitrogen exists at a position distant from the pyridylphenolate site, so that hydrogen bonds and coordination bonds are formed between the molecules, and the intermolecular interaction is strengthened.

  The organolithium complex compounds tend to have deep HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital). In particular, L3BPP and L4BPP are considered to have a lower electron density on the pyridylphenolate side by having a 3-pyridyl group or 4-pyridyl group having higher electron-withdrawing properties than L2BPP. It is known that L2BPP has a narrow band gap and a significantly deep LUMO when nitrogen on the pyridine ring is present on the pyridylphenolate side.

[Electron injection material, organic EL element]
The electron injection material or the organic EL device of the present invention comprises the above-described organic lithium complex compound.
An organic EL element has an ultrathin film layer (hereinafter also referred to as “organic layer”) of 1 μm or less in which a plurality of organic materials having different functions are laminated, and a glass substrate on which ITO (indium tin oxide) as a transparent electrode is formed; It has a structure sandwiched between metal cathodes and typically has an element structure in which a cathode, an electron injection layer, an electron transport layer, a light emitting layer, a hole transport layer, a hole injection layer, and an anode are sequentially stacked. . In the element structure, the electron transport layer may also serve as the light emitting layer, or the hole transport layer may serve as the function of the light emitting layer. Alternatively, a three-layer structure (double hetero structure) in which the light-emitting layer is sandwiched between an electron transport layer and a hole transport layer may be used.

  When a voltage is applied to the organic EL element, holes are injected into the organic layer from the anode side, and electrons are injected from the cathode. The movement of holes and electrons uses the overlap of electron clouds of HOMO for holes and LUMO for electrons. When these carriers are chemically classified, holes correspond to radical cations and electrons correspond to radical anions. When carriers are injected from the electrode into the organic layer, the organic molecule enters an ionic radical state and moves to one electrode while transferring π electrons to adjacent molecules. The radical cation and radical anion recombine in the light-emitting organic material to form a hole-electron pair and generate excitons. Light is observed when the exciton is deactivated.

  In order to maintain or improve the luminous efficiency of the organic EL element, it is effective to lower the energy barrier from the electrode to the organic layer.

  In the present invention, the above-described organolithium complex compound is introduced into the organic layer in the organic EL device as an electron injection material, thereby showing high efficiency in external quantum efficiency-luminance characteristics and power efficiency-luminance characteristics, and having a deep LUMO. I understood it. In particular, L3BPP and L4BPP are considered to have a high energy injecting property due to a smaller energy gap and a deeper LUMO, because hydrogen bonds and coordination bonds are formed in the molecule than L2BPP. It is suitable as an electron injection material for organic EL materials.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not restrict | limited by the following Example.

The equipment and measurement conditions used for the identification of the composites are as follows.
(1) ¹ H nuclear magnetic resonance (NMR) method:
JEOL Ltd. (400 MHz) JNM-EX270FT-NMR type (2) mass spectrometry (MS)
JEOL Ltd. JMS-K9 [Desktop GCQMS] and Waters Ltd. Zspray (SQ detector 2))
(3) Elemental analysis Perkin Elmer 2400II CHNS / O analyzer Measurement mode: CHN mode

[Synthesis Example 1] Synthesis of 2BrPP Into a three-necked flask, 2,6-dibromopyridine, 2-hydroxyphenylboronic acid, toluene, ethanol and a 2M aqueous potassium carbonate solution were added, and then nitrogen bubbling was performed for 1 to 2 hours. Phenylphosphine) palladium (0) (Pd (PPh) ₄ ) was added, and the mixture was heated and stirred for 2 to 3 hours. The consumption of these raw materials was confirmed by thin layer chromatography (TLC) and MS, and the reaction mixture was returned to room temperature. The reaction mixture was washed with saturated brine, extracted with toluene, and dried over anhydrous magnesium sulfate. Magnesium sulfate was filtered off and concentrated to obtain a yellow crystalline solid. This yellow solid was dissolved in hexane / chloroform = 3/2 (vol / vol) (about 100 mL) and placed on a column packed with silica gel. Purification by silica gel column chromatography (silica gel: 500 cc, developing solvent: about 5 L (hexane / chloroform = 3/2 (vol / vol)) gave 2BrPP as a white solid in a yield of 80%.

The results of ¹ H-NMR and MS of 2BrPP are shown below.
¹ H NMR (400 MHz, CDCl ₃ ): δ = 12.71 (s, 1H), 7.84 (d, 1H, J = 7.6 Hz), 7.67 _to 7.75 (m, 2H), 7.32 _to 7.46 (m, 2H), 7.04 (dd, 1H, J = 8.2, 1.2 Hz), 6.93 (dt, 1H, J = 7.6, 1.6 Hz) ppm
MS: m / z 250 [M] ⁺

[Synthesis Example 2] Synthesis of 3BPP Into a three-necked flask, 2BrPP obtained in Synthesis Example 1, 3-pyridineboronic acid ester, toluene, ethanol, and 1.25M tripotassium phosphate aqueous solution were placed, and nitrogen bubbling was performed for 1 to 2 hours. . Thereafter, Pd ₂ (dba) ₃ and tricyclohexylphosphine (PCy ₃ ) were added, followed by heating and stirring for 19 to 21 hours. The consumption of the raw materials was confirmed by TLC and MS, the reaction mixture was returned to room temperature, and then washed with water and ethanol while suction filtration. The filtrate was washed with saturated brine, extracted with toluene, and dried over anhydrous magnesium sulfate. Magnesium sulfate was filtered off and concentrated to obtain a yellow viscous liquid. This orange viscous body was dissolved in chloroform and placed on a column packed with silica gel. Purified by silica gel column chromatography (silica gel: 500 cc, developing solvent: about 1 L (chloroform / ethyl acetate = 19/1 (vol / vol)) => about 3 L (9: 1 (vol / vol)), yield 96% 3BPP was obtained as an orange candy-like solid.

The results of ¹ H-NMR and MS of 3BPP are shown below.
¹ H-NMR (400 MHz, DMSO-d6): δ = 9.22 (d, 1H, J = 1.6 Hz), 8.73 (dd, 1H, J = 4.8, 1.6 Hz), 8.38 (td, 1H, J = 8.0 , 2.0 Hz), 8.26 (d, 1H, J = 7.6 Hz), 8.04 _to 8.17 (m, 3H), 7.63 (q, 1H, J = 4.0 Hz), 7.36 (dt, 1H, J = 8.0, 1.6 Hz _{), 6.96 ~ 7.00 (m,} 2H) ppm
MS: m / z 249 [M] ⁺

[Synthesis Example 3] Synthesis of 4BPP 2BrPP, 4-pyridineboronic acid ester obtained in Synthesis Example 1, toluene, ethanol and a 1.25M tripotassium phosphate aqueous solution were placed in a three-necked flask and bubbled with nitrogen for 1-2 hours. . Thereafter, Pd ₂ (dba) ₃ and tricyclohexylphosphine (PCy ₃ ) were added, followed by heating and stirring for 19 to 21 hours. The consumption of the raw materials was confirmed by TLC and MS, the reaction mixture was returned to room temperature, and then washed with water and ethanol while suction filtration. The filtrate was washed with saturated brine, extracted with toluene, and dried over anhydrous magnesium sulfate. Magnesium sulfate was filtered off and concentrated to obtain a yellow viscous liquid. This yellow viscous liquid was dissolved in chloroform and placed on a column packed with silica gel. Purification by silica gel column chromatography (silica gel = 500 cc, developing solvent: chloroform / ethyl acetate = 19/1 (1 L) => 9: 1 (3 L)) to obtain 4BPP as an orange viscous body with a yield of 89% It was.

The results of ¹ H-NMR and MS of 4BPP are shown below.
¹ H-NMR (400 MHz, DMSO-d6): δ = 8.78 (d, 2H, J = 4.8 Hz), 8.30 (d, 1H, J = 8.4 Hz), 8.08 _to 8.19 (m, 3H), 7.97 ( d, 2H, J = 4.4 Hz), 7.35 (t, 1H, J = 8.0Hz), 6.95 _to 6.99 (m, 2H) ppm
MS: m / z 249 [M] ⁺

[Example 1] Synthesis of Li3BPP Lithium hydroxide hydrate was completely dissolved in methanol in an eggplant flask, and a solution of 3BPP obtained in Synthesis Example 2 dissolved in methanol was added dropwise at a rate of 1 ml / min. did. After stirring for 13 hours after the dropwise addition, the reaction solution was concentrated to obtain an amber powder solid almost quantitatively.

The results of ¹ H-NMR and elemental analysis of Li3BPP are shown below.
¹ H-NMR (400 MHz, DMSO-d6): δ = 9.28 (d, 1H, J = 2.4 Hz), 9.12 _to 9.17 (m, 1H), 8.57 (dd, 1H, J = 4.8, 1.6 Hz), 8.46 (td, 1H, J = 8.0, 2.0 Hz), 8.01 (dd, 1H, J = 8.2, 2.0Hz), 7.57 _to 7.66 (m, 2H), 7.48 (dd, 1H, J = 8.0, 4.4 Hz) , 6.77 _to 6.82 (m, 1H), 6.32 to 6.37 (m, 1H), 6.07 (t, 1H, J = 7.2 Hz) ppm (see Fig. 1)
Anal.Calcd for C ₁₆ H ₁₁ LiN ₂ O; C, 75.59; H, 4.36; N, 11.02%. Found: C, 75.64; H, 4.24; N, 10.98%

[Example 2] Synthesis of Li4BPP Lithium hydroxide hydrate was completely dissolved in methanol in a recovery flask, and a solution of 4BPP dissolved in methanol was added dropwise thereto at a rate of 1 ml / min. After stirring for 12 hours after the dropping, the reaction solution was concentrated to obtain a yellow powdered solid almost quantitatively.

The results of ¹ H-NMR and elemental analysis of Li4BPP are shown below.
¹ H-NMR (400 MHz, DMSO-d6): δ = 9.20 (br, 1H), 8.69 (d, 2H, J ­ = 6.4 Hz), 8.07 _to 8.11 (m, 3H), 7.74 (d, 2H, J ­ = 4.4 Hz), 6.86 (t, 1H, J ­ = 8.0 Hz), 6.41 (d, 1H, J ­ = 8.8 Hz), 6.17 (t, 1H, J ­ = 5.6 Hz) ppm (see Figure 2) )
Anal.Calcd for C ₁₆ H ₁₁ LiN ₂ O; C, 75.59; H, 4.36; N, 11.02%. Found: C, 75.43; H, 4.25; N, 11.00%

[Reference example]
As a reference example, Li2BPP represented by the following structural formula was used.

[Thermal properties evaluation]
(1) Decomposition point (T _d5 )
The samples (Li3BPP, Li4BPP) obtained in Examples 1 and 2 and the sample of the reference example (Li2BPP) were each placed on an aluminum pan, and a differential thermogravimeter (manufactured by PerkinElmer Japan, Inc .; TGA diamond) was used. The 5% weight loss temperature (T _d5 ) was measured in a nitrogen gas at a heating rate of 10 ° C./min.
(2) Melting point ( _Tm )
Each sample was sealed in an aluminum pan, and the melting point (T _m ) was measured at a heating rate of 10 ° C./min in nitrogen gas using a differential scanning calorimeter (manufactured by Perkin Elmer Japan; DSCDTA). .
(3) Sublimation point (T _s )
Each sample is placed on a platinum pan, and the temperature rise rate is 10 ° C./min in vacuum (10 ⁻⁴ Pa) using an organic color material thermal behavior measuring device (manufactured by ULVAC, Inc .; VAP-9000 special model). The sublimation point (T _s ) was measured at.
The results are shown in Table 1.

Li2BPP, Li3BPP, and Li4BPP all had the same molecular weight, and despite the difference only in the substitution position of pyridine, there was a clear difference in physical property values. That is, Td ₅ was obtained in the order of Li2BPP <Li3BPP <Li4BPP. The reason for this is that Li2BPP has nitrogen in the position closest to the pyridylphenolate moiety, so it is easy to form an intramolecular hydrogen bond or an intramolecular coordination bond with lithium, but in Li3BPP and Li4BPP, pyridylphenolate This is probably because the presence of nitrogen at a position distant from the site results in the formation of hydrogen bonds and coordination bonds between molecules, and the interaction between molecules is strengthened.

[Optical characteristics evaluation]
(1) UV-vis absorption spectrum A thin film of Li2BPP, Li3BPP, Li4BPP vacuum-deposited on a quartz substrate, and a 1 × 10 ⁻⁵ M tetrahydrofuran solution in which Li2BPP, Li3BPP, Li4BPP are dissolved in tetrahydrofuran are 1 cm × 1 cm × 1 cm. Measurements were made on samples placed in a quartz cell. Shimadzu Corporation UV-3150 was used for the measurement. As measurement conditions, the scan speed was medium speed, the measurement range was 200 to 800 nm, the sampling pitch was 0.5 nm, and the slit width was 0.5 nm.
(2) Evaluation of electrochemical properties Li2BPP, Li3BPP, and Li4BPP thin films vacuum-deposited on an ITO glass substrate were subjected to ionization potential in vacuum using an ionization potential measuring device (PYS) manufactured by Sumitomo Heavy Industries, Ltd. Ip) was measured. Moreover, the energy gap (Eg) was estimated from the absorption edge of the UV-vis absorption spectrum, and the electron affinity (Ea) was calculated.
(3) Fluorescence spectrum The fluorescence spectrum was measured about the thin film of Li2BPP, Li3BPP, and Li4BPP vacuum-deposited on the quartz substrate. For the measurement, Instruments S.D. A. Fluoro MAX-2 manufactured by the company was used.

The results are shown in Tables 2 and 3 and FIGS.

  In Li3BPP and Li4BPP, the nitrogen position of the pyridine ring was different from that of Li2BPP, so that HOMO and LUMO tended to be deeper, similar to the calculated values. In the LUMO of Li2BPP and Li3BPP, there was no difference in the calculated value, but there was a large difference of 0.3 eV in the actually measured value. From this result, it is considered that LUMO can be deepened by introducing a 3-pyridyl group or a 4-pyridyl group having high electron withdrawing properties. However, while HOMO and LUMO became deeper, there was no significant difference in the energy gap. This is presumably because Li2BPP, Li3BPP, and Li4BPP do not differ greatly in molecular structure as the energy gap differs.

[Element characteristic evaluation 1]
(I) Fabrication of coating type yellow-green element As shown in FIG. 7, polystyrene sulfonic acid (PEDOT: PSS) was spin-coated on an ITO glass substrate as a hole injection layer, baked, and formed into a film. Similarly, an interlayer HT12 (manufactured by Sumitomo Chemical Co., Ltd., thermally crosslinkable polymer material) was formed on the hole transport layer, and F8BT and an electron injection layer (EIL) were stacked on the light emitting layer. Each of Li3BPP, Li4BPP, and Li2BPP was used for the electron injection layer.
Over the layer, aluminum was deposited as a cathode by vacuum deposition.
That is, the element structure was [ITO / PEDOT: PSS (30 nm) / IL (20 nm) / F8BT (80 nm) / EIL (1 nm) / Al (100 nm)] (EIL = Li3BPP, Li4BPP, Li2BPP).
For comparison, an element (NonEIL) that does not use an electron injection layer was produced.

(Ii) Luminescence evaluation Evaluation of element characteristics was performed by measuring an EL spectrum using a photonic multichannel spectrometer (manufactured by Hamamatsu Photonics; PMA-1).
Looking at the light emitting surface, yellow-green light emission could be observed in all the devices in which the electron injection layer was inserted, whereas in the device not using the electron injection material, only the light emitting surface light was emitted. Therefore, in an element that does not use an electron injecting material, the brightness required for each element characteristic cannot be obtained, and the characteristic cannot be measured.
EL spectrum, current density-voltage characteristic relationship, luminance-voltage characteristic relationship, power efficiency-luminance characteristic relationship, current efficiency-luminance relationship of each element when Li2BPP, Li3BPP and Li4BPP are used for each electron injection layer The relationship between the characteristics and the relationship between the external quantum efficiency and the luminance characteristics are shown in FIGS.

  In the EL spectrum, light emission derived from F8BT was observed. From the current density-voltage characteristics, it was found that the voltage was drastically reduced by insertion compared to a device in which no electron injection layer was inserted. Therefore, it can be seen that Li3BPP and Li4BPP function as an electron injection layer.

[Element characteristic evaluation 2]
(I) Fabrication of device using polymer binder To improve the film-forming property, as an electron injecting layer, a device obtained by mixing 30 wt% of polyvinyl pyridine (PV4Py) with each of Li2BPP, Li3BPP, and Li4BPP is used. A device was fabricated in the same manner as in Evaluation 1.
For comparison, an element using only PV4Py for the electron injection layer was produced.

(Ii) Luminous evaluation Luminous evaluation was performed in the same manner as in the device characteristic evaluation 1.
FIG. 16 to FIG. 16 show the EL spectrum, current density-voltage characteristic relationship, luminance-voltage characteristic relationship, power efficiency-luminance characteristic relationship, current efficiency-luminance characteristic relationship, and external quantum efficiency-luminance characteristic relationship of each element. 21 and the results are shown in Table 5.

From FIG. 14, in the EL spectrum, a spectrum derived from F8BT was observed.
Even in the element system using the polymer binder, the voltage was increased in the order of Li2BPP <Li3BPP <Li4BPP as in the case of the element not using the polymer binder (FIG. 15). In power efficiency, current efficiency, and external quantum efficiency, the efficiency decreased in the order of Li2BPP>Li3BPP> Li4BPP (FIGS. 17, 18, and 19). On the other hand, when the light emission start voltage and the drive voltage were compared with an element not using the polymer binder, Li2BPP had a voltage reduction of 0.05 to 0.34V. On the other hand, Li3BPP and Li4BPP were increased in voltage by 0.02 to 0.19V.

Claims (3)

Organolithium complex compound represented by the following formula (1)

(In the formula (1), Ar represents a triazinyl group, a 3-pyridyl group or a 4-pyridyl group ).   An electron injection material comprising the organolithium complex compound according to claim 1.   An organic EL device using the organolithium complex compound according to claim 1.

Images