CN101525335A - Full-bridge linked triphenylamine compound and application thereof in electroluminescent device - Google Patents

Abstract

The invention discloses triphenylamine compounds with full-bridge rigid structures and electroluminescent devices using them as hole-transporting layer materials. The general structural formula of this type of compound is the right formula, wherein R is the same hydrogen atom, phenyl, 4-triphenylamine or 3-(N-p-tert-butylphenyl)carbazolyl. The triphenylamine compound of the present invention has high thermal stability, and the synthesis method is simple and feasible, and the compound can be prepared by a spin-coating process to prepare an electroluminescent device, has low cost and is suitable for wide application. The triphenylamine compound of the invention is used as an electroluminescence device made of a hole transport material, has high efficiency and high brightness electroluminescence performance, and can be widely used in the field of organic electroluminescence.

Description

Fully bridged triphenylamine compounds and their applications in electroluminescent devices

technical field

The invention relates to a triphenylamine compound with a full-bridge rigid structure and its application as a hole transport material in an electroluminescent device, belonging to the field of organic electroluminescent materials.

Background technique

Since 1987, when CW Tang et al. of Kodak reported for the first time that a double-layer device structure with Alq ₃ as a light-emitting material was prepared by vacuum evaporation, organic electroluminescence has attracted great attention.

In order to obtain devices with high luminous efficiency, devices with multilayer structures have been receiving extensive attention. The so-called multilayer device generally includes the following layers: hole injection layer, hole transport layer, light emitting layer, hole blocking layer, electron transport layer, electron injection layer. Among them, the hole transport layer generally contains an aromatic amine structure, and the lone pair of electrons of the nitrogen atom is used to transport holes, such as the most commonly used hole transport material 1,4-bis(1-naphthylphenylamine)-biphenyl ( NPB).

However, the glass transition temperature of NPB molecules is only 95 °C, and the thermal stability is not high, which limits its application in electroluminescent devices. In addition, NPB molecules are manufactured using a vacuum sublimation film-forming process, which is time-consuming and expensive.

In order to improve the thermal stability of traditional hole-transporting materials, Shirota proposed the concept of "star-shaped molecule", which is different from the traditional "linear molecule". He connected aromatic amine molecules around phenyl or triphenylamine, and the obtained molecules Due to the crowded space and the large molecular weight, it is difficult for molecular crystallization to occur, thereby improving the thermal stability of the molecule.

In theory, in 1999, Sakaki proposed the concept of "planar nitrogen", that is, when the central nitrogen atom and the surrounding aromatic groups have a certain degree of conjugation, the hole transport performance is better. The adjacent phenyl groups are in a twisted state, which reduces the conjugation of the molecule, and the nitrogen cations formed in the transport are sp ² hybridized, so the molecular reformation energy is higher. He predicted that if the nitrogen atom can be placed in a more planar state than the surrounding phenyl groups, more excellent hole-transporting materials can be obtained. Such model molecules have not been synthesized so far, and are only at the theoretical stage.

Contents of the invention

The purpose of the present invention is to make up for the deficiencies of the prior art, to provide triphenylamine compounds with a full bridge rigid structure and applications thereof, the triphenylamine compounds meet the requirements of the Sakaki theory, and they are used as hole-transport materials to prepare electro-induced The light-emitting device has high-efficiency light-emitting performance.

其中R为彼此相同的氢原子、苯基、4-三苯胺基或3-(N-对叔丁基苯基)咔唑基，也即R为彼此相同的-H、

Said triphenylamine compound with full bridge rigid structure of the present invention, its structure is as shown in formula (1):

Wherein R is the same hydrogen atom, phenyl, 4-triphenylamino or 3-(N-p-tert-butylphenyl)carbazolyl, that is, R is the same -H,

The triphenylamine compound with a full-bridge rigid structure mentioned in the present invention is used as a hole-transporting material of an electroluminescent device.

The electroluminescent device of the present invention comprises a cathode layer, a luminescent layer, a hole transport layer and a conductive glass substrate layer attached to glass that are bonded in sequence, wherein the material used for the hole transport layer is the formula (1) described compound.

In the present invention, the triphenylamine units with hole transport properties are bridged to form a full bridge structure. Compared with triphenylamine units without bridges or partial bridges, the molecular rigidity of the triphenylamine compounds of the present invention is larger and thermally The stability is higher, and the molecular conjugated skeleton is more planar, which strengthens the conjugation ability between the central nitrogen atom and the surrounding benzene ring, which is conducive to the transport of holes, which meets the requirements of Sakaki theory, and they are used as holes in electroluminescent devices. The hole transport material can greatly improve the thermal stability of the device, and can obtain high-efficiency electroluminescence performance. The green light device based on Alq ₃ prepared by the present invention has a maximum brightness of 39051cd/m ² and a maximum current efficiency of 6.48cd/A, which is obviously better than 4.29cd/A of the traditional NPB. At the same time, the spin-coating process can be used when preparing the electroluminescent device, and the cost is lower than that of the vacuum sublimation film-forming process.

Description of drawings

One of the hole transport materials of the present invention, 2,6,10-tris(3-(N-p-tert-butylphenyl)carbazolyl)-4,8,12-tris(xylylmethylene) in Fig. 1 Base) the ultraviolet-visible absorption spectrogram of bridging triphenylamine solution;

2, one of the hole transport materials of the present invention, 2,6,10-tris(3-(N-p-tert-butylphenyl)carbazolyl)-4,8,12-tris(xylylmethylene) base) photoluminescence figure of bridged triphenylamine solution;

Fig. 3 structural representation of the electroluminescence device of the present invention;

Figure 4 is the emission spectrum of the electroluminescent device of the present invention.

Detailed ways

The present invention will be further described below through specific examples, the purpose of which is to help better understand the content of the present invention, but these specific examples do not limit the protection scope of the present invention in any way.

The raw materials used in the examples of the present invention are known compounds, which can be purchased in the market, or can be synthesized by methods known in the art.

Example 1

Preparation of 4,8,12-tris(xylylmethylene) bridged triphenylamine (abbreviated as HTM1)

3.87g p-bromotoluene (22.6mmol) was dissolved in 30ml absolute ether in a Schlenk tube. 9.3ml of n-BuLi (2.45M, 22.8mmol) was dropped into the Schlenk tube at -10°C, and reacted at low temperature for 1 hour after the drop was completed. Dissolve 0.90g of 2,2',2"-triphenylamine tricarboxylate (2.15mmol) in 20ml of absolute anhydrous THF and drop it into a Schlenk tube to react for 3h. After the reaction, quench with dilute NH ₄ Cl solution. Diethyl ether Extract.Separate the organic phase, wash it with water three times, and dry it with anhydrous Na ₂ SO _4.The organic solvent is spin-dried, and the obtained crude product is dissolved in 30ml glacial acetic acid, and heated to reflux.Carefully drop into 3ml concentrated HCl, and react for 3h.Reaction After finishing, solution is poured into 200ml ice water.20ml chloroform is extracted three times respectively, obtains red solution.After spin-drying chloroform, thick product uses sherwood oil: dichloromethane=2: 1 (volume ratio) cross column separation, obtains white solid 1.48g, Yield 84%. Characterized by ¹ H NMR, ¹³ C NMR and MS, the white solid was confirmed to be HTM1. ¹ HNMR (300MHz, CDCl ₃ , δ): 6.93 (t, J=6.6Hz, 3H), 6.83-6.81 (n, 18H), 6.63 (d, J=8.1Hz, 12H), 2.27 (s, 18H); ¹³ C NMR (75MHz, CDCl ₃ , δ): 143.58, 135.41, 135.35, 130.29, 128.86, 128.25, 128.20 , 122.45, 55.38, 21.14.Anal.Calcd.for C ₆₃ H ₅₁ N (%): C, 92.04; H, 6.25; N, 1.70.Found: C, 92.21; H, 6.20; )m/z: 821.9[M ⁺ ].

Example 2

Preparation of 2,6,10-triphenyl-4,8,12-tris(xylylmethylene) bridged triphenylamine (abbreviated as HTM2)

1.00 g (1.22 mmol) of 4,8,12-tris(xylylmethylene) bridged triphenylamine was dissolved in 20 ml of chloroform in a 50 ml round bottom flask. 0.68 g NBS (3.82 mmol) was added. The reaction was stirred at room temperature for 12h. After the reaction, the organic phase was washed with water three times. Dry over anhydrous Na ₂ SO ₄ . Use petroleum ether: dichloromethane = 3: 1 (volume ratio) for column separation. 1.22 g of white solid 2,6,10-tribromo-4,8,12-tris(xylylmethylene) bridged triphenylamine was obtained with a yield of 95%. ¹ H NMR (300MHz, CDCl ₃ , δ): 6.91(s, 6H), 6.86(d, J=8.1Hz, 12H), 6.55(d, J=8.1Hz, 12H), 2.30(s, 18H); ¹³ C NMR (75MHz, CDCl ₃ , δ): 141.809, 136.132, 134.261, 130.772, 130.701, 130.001, 128.697, 116.098, 55.293, 21.124. Ahal. Calcd. for C ₆₃ H ₄₈ Br ₃ N (%): C, 71.47; H, 4.57; N, 1.32. Found: C, 71.23; H, 4.40; N, 1.35; MALDI-TOF-MS: m/z 1059.2 (M ⁺ ).

2,6,10-Tribromo-4,8,12-tris(xylylmethylene) bridged triphenylamine (600mg, 0.57mmol), phenylboronic acid (276mg, 2.26mmol), Pd(PPh ₃ ) ₄ (1.81 g, 17.1 mmol) and potassium carbonate (1.81 g, 17.1 mmol) were dissolved in 40 ml toluene and 9 ml distilled water in a Schlenk bottle. Reflux reaction 2d. Extracted with CHCl ₃ , dried over anhydrous sodium sulfate, spin-dried the solvent, and separated by column with petroleum ether:dichloromethane=3:1 (volume ratio). 506 mg of white solid was obtained with a yield of 85%. Characterized by ¹ H NMR, ¹³ C NMR and MS, it was confirmed that the white solid was HTM2. ¹ H NMR (300MHz, CDCl ₃ , δ): 7.27-7.14(m, 21H), 6.87(d, J=8.1Hz, 12H), 6.74(d; J=8.1Hz, 12H), 2.29(s, 18H ); ¹³ C NMR (300MHz, CDCl ₃ , δ): 143.246, 140.855, 135.529, 134.742, 130.332, 129.445, 128.829, 128.443, 126.753, 55.771, 21.211. Anal. Calcd. for C ₈₁ % H ₆₃ C, 92.62; H, 6.05; N, 1.33. Found: C, 92.46.15; H, 6.27; N, 1.24. Ms MALDI-TOF m/z 1049.8 [M ⁺ ].

Example 3

Preparation of 2,6,10-tris(4-triphenylamino)-4,8,12-tris(xylylmethylene) bridged triphenylamine (abbreviated as HTM3)

HTM3 can be prepared in a similar manner to Example 2. ¹ H NMR (300MHz, CDCl ₃ , δ): 7.18-7.15(m, 18H), 7.05-6.91(m, 30H), 6.78(d, J=7.2Hz, 12H), 6.65(d, J=7.2Hz , 12H), 2.21(s, 18H).Anal.Calcd.for C ₁₁₇ H ₉₀ N ₄ (%): C, 90.54; H, 5.85; N, 3.61.Found: C, 91.01; H, 6.16; N, 3.36; MALDI-TOF-MS: m/z 1551.5 (M ⁺ ).

Example 4

2,6,10-tris(3-(N-p-tert-butylphenyl)carbazolyl)-4,8,12-tris(di-p-tolylmethylene) bridged triphenylamine (abbreviated as HTM4) preparation of

HTM4 can be prepared in a similar manner to Example 2. ¹ H NMR (300MHz, CDCl ₃ , δ): 7.99(d, J=8.1Hz, 3H), 7.52(d, J=8.1Hz, 9H), 7.37-7.26(m, 24H), 6.83-6.76(m , 27H), 2.25 (s, 18H), 1.341 (s, 27H). Anal. Calcd. for C ₁₂₉ H ₁₀₈ N ₄ (%): C, 90.38; H, 6.35; N, 3.27. Found: C, 90.71 ; H, 6.63; N, 2.94. MALDI-TOF-MS: m/z 1713.6 (M ⁺ ). Figure 1 and Figure 2 are 2,6,10-tri(3-(N-p-tert-butylphenyl Carbazolyl))-4,8,12-tris(xylylmethylene) bridged triphenylamine solution UV-visible absorption spectrum and photoluminescence.

Example 5

As shown in Figure 3, the electroluminescent device prepared by the triphenylamine compound of the present invention comprises a cathode layer 4, a light-emitting layer 3, a hole transport layer 2 and a conductive glass substrate layer 1 attached to the glass which are sequentially laminated, and also That is, the cathode layer is bonded to the light-emitting layer, the light-emitting layer is bonded to the hole transport layer, and the hole transport layer is bonded to the conductive glass substrate layer; wherein, the material of the conductive glass substrate layer 1 can be ITO, and the material of the hole transport layer 2 The material is the triphenylamine compound of the present invention, the material of the light-emitting layer 3 can be 8-hydroxyquinoline aluminum, and the material of the cathode layer 4 can be lithium fluoride/aluminum.

The electroluminescent device can be fabricated by methods known in the art, such as the methods disclosed in the reference (Adv. Mater. 2003, 15, 277.). The specific method is as follows: under high vacuum conditions, spin-coat a 40nm hole transport layer on a cleaned conductive glass (ITO) substrate, and then vapor-deposit 50nm of Alq ₃ , 1nm of LiF and 120nm of Al. The device shown in Figure 3 is made by this method, and the structures of various devices are as follows:

Device 1 (D1):

ITO/HTM3(40nm)/Alq ₃ (50nm)/LiF(1nm)/Al(120nm)

Device 2 (D2):

ITO/HTM4(40nm)/Alq ₃ (50nm)/LiF(1nm)/Al(120nm)

Device 3 (D3):

ITO/NPB(40nm)/Alq ₃ (50nm)/LiF(1nm)/Al(120nm)

The current-brightness-voltage characteristics of the device were completed by a Keithley source measurement system (Keithley 2400 Sourcemeter, Keithley 2000 Currentmeter) with a calibrated silicon photodiode. The electroluminescence spectrum was measured by a SPEX CCD3000 spectrometer from JY Company in France. All measurements All completed in room temperature atmosphere.

The performance data of each device is shown in the table below:

device Maximum brightness cd/m ² Highest current efficiency cd/A Luminescence Spectrum Device 1 39051 4.51 - Device 2 24496 6.48 Figure 4 Device 3 39058 4.29 -

Device 2 emits green light, and its maximum current efficiency is as high as 6.48cd/A. Compared with device 3 used as a comparison, its current efficiency is significantly improved, and the hole transport layers of device 1 and device 2 are prepared by spin coating process , which greatly reduces the manufacturing cost and time of the device. Compared with other hole transport materials, the hole transport material of the present invention utilizes traditional triphenylamine molecules to achieve a more planar molecular skeleton and improve molecular rigidity, therefore, it is beneficial to the stability of the device and to obtain Excellent electroluminescence performance is conducive to the development of high-efficiency full-color displays.

Claims (3)

1. There is the triphenylamine compound of full-bridging rigid structure, and its structural general formula is:

wherein R is the same hydrogen atom, phenyl, 4-triphenylamino or 3-(N-p-tert-butylphenyl)carbazolyl. 2. The application of the triphenylamine compound with full bridge rigid structure as claimed in claim 1 as a hole transport material in an electroluminescent device. 3. an electroluminescent device prepared by a triphenylamine compound as claimed in claim 1, comprising sequentially bonded cathode layer, luminescent layer, hole transport layer and the conductive glass substrate layer attached to the glass, is characterized in that: The material of the hole transport layer is the full bridged triphenylamine compound as claimed in claim 1.

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