TWI393762B - Organic electroluminescent device and host material thereof - Google Patents

Description

Organic electroluminescent device and its main illuminant material

The invention relates to a fluorescent main illuminant material suitable for an organic electroluminescent device, in particular to a green fluorescent main illuminant material.

In 2005, Nippon Petrochemical Co., Ltd. and Sony Corporation announced that they will jointly develop materials for organic light-emitting diode (OLED) and share existing OLED materials and device technologies and patents. In 2007, Sony released the world's first OLED display, and in 2009, Japan's Cenatec 2009 exhibition released "flexible OLED", and is expected to launch a large-size OLED TV in 2010. The OLED display does not require a backlight module, and has the advantages of low driving voltage, high brightness, high contrast, wide viewing angle, fast response, simple structure, ultra-thin film, light weight, etc., and has gradually impacted the current market dominated by LCD displays. And with the skill of the technology, it entered the stage of contending.

The organic light-emitting diode system is based on the principle of organic electroluminescence (OEL), that is, the luminescence phenomenon in which an organic substance is excited by a corresponding electric energy under a certain electric field. Depending on the luminescent materials, OLEDs can be classified into small molecule series and polymer series. The small molecule luminescent material comprises a host illuminant material and a guest material (also known as a fluorescent material), and the main developing countries are Asian countries such as Japan, Korea and the Republic of China. The polymer series is mainly based on European and American countries.

In 1963, when Popel et al. studied the 10~20μm thick anthracene single wafer, it was first discovered that after applying 400 volts across the crystal, blue fluorescence could be observed, which led to the study of organic electroluminescence. The first step is taken, but since the single crystal grows and the area is difficult, and the required driving voltage is too large, the luminous efficiency is inferior to that of the inorganic material, so it has no practical value. Subsequently, Helfrich and Williams and others continued their efforts to reduce the voltage to about 100 volts, and obtained an external quantum efficiency of about 5% photon/electron. However, since the thickness of the single crystal is too large, the driving voltage is also high, resulting in electrical energy conversion. The efficiency of light energy is too low. In 1982, Vincett et al. made a 50 nm thick tantalum film by vacuum evaporation, and further reduced the driving voltage to 30 volts to observe blue fluorescence, but the electron injection efficiency was too low and the film formation of germanium was observed. Not good, so its external quantum efficiency is only about 0.03%. After more than 20 years of sporadic development, there have been no major breakthroughs.

It was not until 1987 that the Eastman Kodak company Tang and Van Slyke first published organic light-emitting diodes (OLEDs) that they had a breakthrough. They used aromatic diamine (HTM-2) as a hole transport layer material and a film-forming 8-hydroxyquinolate aluminum (III) as an electron transport layer and luminescent material. Vacuum evaporation is used to form a film of 60-70 nm, and a low-work function magnesium-silver alloy is used as a cathode to improve the injection efficiency of electrons and holes. Inserting the organic small molecule luminescent material developed between the two electrodes, it emits light when energized, which produces green light with a wavelength of 530 nm, which can exhibit low driving voltage, high quantum efficiency (>1%) and components. The effect of stability and the like greatly enhances the characteristics and practicability of the organic small molecule electroluminescent device.

Then in 1990, Friend et al. of Cambridge University in the United Kingdom subsequently published polymer light-emitting diodes (PLEDs) to spin-coat the conjugated polymer PPV (poly(p). -phenylene vinylene)) as a light-emitting layer, a polymer electroluminescent device having a single-layer structure is produced, which has a simple process, good mechanical properties of a polymer, and semiconductor-like properties, so that a conjugated polymer luminescent material is used. Research is developing rapidly.

The material determines whether the OLED product is good or not. The luminescent material is the most important material. The good luminescent material must meet four conditions: (1) high quantum efficiency fluorescence characteristics, and the fluorescence spectrum is mainly distributed in the visible light region of 400-700 nm. (2) good semiconductor characteristics, high conductivity, ability to conduct electrons or holes, or both; (3) good film formation, no pinholes in tens of nanometers of film (4) Good thermal stability.

Most of the electron transport layer and the hole transport layer can be used as luminescent materials in the visible light region, but since most organic materials exceed a certain concentration, especially in the solid state, there will be self quenching or concentration. The problem of concentration quenching leads to broadening of the emission peak or red shift, so the fluorescent dopant is generally doped in a low concentration manner in the fluorescence with certain carrier properties. The main illuminant material acts as a dopant emitter. Several design considerations for fluorescent primary illuminant materials and fluorescent dopants for small molecule organic electroluminescent devices are: (1) fluorescent dopants have high fluorescence efficiency; (2) fluorescent blending The absorption spectrum of the impurity and the emission spectrum of the fluorescent main emitter material should be well overlapped so that the energy can be efficiently transmitted from the host to the guest; (3) there are red, blue, green or yellow emission peaks, and the emission The peak is as narrow as possible to maintain the purity of the light color; (4) the stability is good and can be evaporated.

A commonly used green fluorescent host material is 9,10-di-(2-naphthyl) anthracene (ADN, such as the following chemical formula (A)) or DNPBA (WO2007021117, such as the following chemical formula (B)) In response to the trend of large-scale OLED panels, these commonly used green fluorescent host materials face the technical bottleneck of excessive power consumption of the panel. Therefore, it is necessary to develop a new type of green fluorescent host material and components with high efficiency and low voltage to solve the problem of excessive power consumption of large-size OLED panels.

Therefore, the main object of the present invention is to provide a green fluorescent main illuminant material, which has the advantages of high stability, easy preparation, easy commercialization, and industrial application value, so as to solve the problem of excessive power consumption of large-sized OLED panels. .

Another object of the present invention is to provide an organic electroluminescent device comprising the green fluorescent main illuminant material of the present invention, which has the advantages of high efficiency and low voltage, and has no excessive power consumption of a conventional large-sized OLED panel. The problem.

In order to achieve the above object, the present invention provides a fluorescent main illuminant material having the structure represented by the following chemical formula (I):

Wherein the Ar ₁ and Ar ₂ systems are each independently a C ₆ -C ₂₀ aromatic ring.

In a preferred embodiment, the fluorescent primary illuminant material is a compound of the formula:

In a preferred embodiment, the fluorescent system is green fluorescent.

The present invention further provides a fluorescent luminescent composition comprising: a fluorescent main illuminant material as described above; and a fluorescent dopant.

The present invention further provides an organic electroluminescent device comprising a layered structure arranged in the following order: a transparent substrate, an anode layer, a hole transport layer, a light emitting layer, an electron transport layer and a cathode layer; wherein the organic motor emits light The device is characterized in that the luminescent layer contains the aforementioned fluorescent main illuminant material.

In a preferred embodiment, the organic electroluminescent device further includes a hole injection layer.

In a preferred embodiment, the organic electroluminescent device further includes an electron injecting layer.

In a preferred embodiment, the anode layer and the cathode layer are respectively in contact with an external power source to form an electrical path.

In a preferred embodiment, the luminescent layer further comprises a fluorescent dopant.

In a preferred embodiment, the fluorescent dopant is green having the characteristics of Commission Internationale d'Exclairage (CIEx, y), wherein CIEx is between 0.26 and 0.36, and CIEy is between 0.60 and 0.68. Fluorescent dopants; for example, C545T.

The fluorescent main light-emitting device of the invention has the advantages of high stability, easy preparation, easy commercialization and industrial application value, and therefore the organic electroluminescent device of the invention using the fluorescent main light-emitting material has high efficiency and The advantages of low voltage and can solve the problem of excessive power consumption of large-size OLED panels.

The present invention relates to a fluorescent main illuminant material, and a fluorescent luminescent composition and an organic electroluminescent device comprising the luminescent main illuminant material.

The fluorescent main illuminant material of the present invention has the structure shown by the following chemical formula (I):

Wherein the Ar ₁ and Ar ₂ systems are each independently a C ₆ -C ₂₀ aromatic ring.

An embodiment of the organic electroluminescent device of the present invention comprises a layered structure arranged in the following order: a transparent substrate, an anode layer, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and The cathode layer; wherein the anode layer and the cathode layer are respectively in contact with an external power source to form an electrical path, and the selection of materials of the layers other than the light-emitting layer is generally known in the art without limitation. For example, the transparent substrate may be glass, plastic or other flexible substrate; the anode layer may be, but not limited to, indium tin oxide (ITO); the hole injection layer may be, but not limited to, a copper-titanium-based material. (Phthalocyanine) such as copper phthalocyanine (CuPC) or allylamine-based material; the aforementioned hole transport layer may be, but not limited to, NPB (n, n'-bis (naphthalen-1-yl)-n, n'- Bis(phenyl)-benz idine); the foregoing electron transport layer may be an aluminum fault compound such as, but not limited to, tris(8-hydroxyquinoline)aluminum (Alq3); the electron injection layer may be an alkali metal or lithium fluoride An organic layer of lithium oxide, a lithium complex compound or a doped alkaline metal; the foregoing cathode layer may be, but not limited to, aluminum, an aluminum lithium alloy, a magnesium silver alloy, lithium fluoride or a mixture thereof.

In the selection of the luminescent layer material of the small molecule organic electroluminescent device, a fluorescent main illuminant material is usually used together with a fluorescent dopant to achieve the effect of electroluminescence. The organic electroluminescent device of the present invention is characterized in that the luminescent layer of the present invention comprises the fluorescent luminescent composition of the present invention comprising the fluorescent main illuminant material of the above formula (I) and a luminescent dopant. .

Preferably, the fluorescent primary illuminant material of the present invention forms a luminescent layer together with the green fluorescent dopant. The green fluorescent dopant includes, but is not limited to, C545T.

The following embodiments are intended to further understand the advantages of the present invention and are not intended to limit the scope of the invention.

Example 1: Preparation of the fluorescent main illuminant material of the present invention (chemical formula Inv-1) Synthesis of [2,6-Bis-(10-naphthalen-2-yl-anthracen-9-yl)-pyridine) ]

10.00 g (42.2 mmol) of 2,6-dibromopyridine, 33.07 g (94.97 mmol) of 9-(naphthalen-7-yl)indole-10-yl-boronic acid (9-( Naphthalene-7-yl)anthracene-10-yl-10-boronic acid), 2.33 g (2.11 mmol) of tetrakis(triphenylphosphine)palladium(0)), 150 ml of toluene, 15 ML of ethanol and 63 ml of sodium carbonate (2M) were refluxed overnight (overnight, 20 hours) under nitrogen, cooled and filtered to remove the solid. After drying, the finished product was 26.2 g, and the purity was 99.26%. The yield was 90.8%. The product was purified by sublimation to a purity of 99.6%, a melting point of 487.8 ° C, and a glass transition temperature (Tg) of 170 ° C.

Example 2: Preparation of the fluorescent main illuminant material of the present invention (chemical formula Inv-2) Synthesis of [2,5-Bis-(10-naphthalen-2-yl-anthracen-9-yl)-pyridine) ]

10.00 g (35.2 mmol) of 5-bromo-2-iodo-pyridine, 27.6 g (79.23 mmol)

10.00 g (35.2 mmol) of 5-bromo-2-iodo-pyridine, 27.6 g (79.23 mmol) of 9-(naphthalen-7-yl)indole-10-yl Boric acid (9-(naphthalene-7-yl)anthracene-10-yl-10-boronic acid), 2.03 g (1.76 mmol) of tetrakis(triphenylphosphine) palladium(0)), 150 ml of toluene, 15 ml of ethanol and 53 ml of sodium carbonate (2M) were refluxed overnight (overnight, 20 hours) under nitrogen, cooled and filtered to remove the solid, which was dried to give the finished product 14.62. The gram has a purity of 98% and a yield of 61%. The product was purified by sublimation to a purity of 99.5%, a melting point of 430.9 ° C, and a glass transition temperature (Tg) of 187 ° C.

The NMR ( ¹ H NMR, 400 MHz) spectral data is as follows: δ 9.10 (s, 1H), 8.03-8.15 (m, 7H), 7.90-7.99 (m, 7H), 7.77-7.82 (m, 4H), 7.60 - 7.67 (m, 6H), 7.50-7.56 (m, 4H), 7.36-7.43 (m, 4H).

Example 3: Test data of the organic electroluminescent device of the present invention

The characteristics of the organic electroluminescent device of the present invention and the organic electroluminescent device of the comparative example were tested in this example. The organic electroluminescent device of the present invention is characterized in that the luminescent layer uses the fluorescent main illuminant material of the present invention (a compound of Inv-1 or Inv-2), and in addition, the organic electro-excitation of the present embodiment and the comparative example The materials used in the other layers of the optical device are identical:

‧ substrate: glass;

‧ anode layer: indium tin oxide (ITO);

‧ hole injection layer: 50 nm copper cyanide (CuPC);

‧ hole transport layer: 25nm NPB (n, n'-bis (naphthalen-1-yl)-n, n'-bis (phenyl)-benzidine);

‧ luminescent layer: main illuminant material (Inv-1, Inv-2 compound or ADN) and C545T as green light dopant, doping concentration 1%;

‧ Electron transport layer: 20 nm tris(8-hydroxyquinoline) aluminum (Alq3);

‧ Electron injection layer: 0.7 nm lithium fluoride (LiF);

‧ Cathode layer: 150 nm aluminum.

The above layers are sequentially combined by vacuum evaporation. The main illuminant material of the luminescent layer of the organic electroluminescent device of the present invention uses the luminescent main illuminant material (Inv 1 or Inv 2) of the present invention; the main illuminant material of the luminescent layer of the comparative example uses 9,10 - 9,10-di-(2-naphthyl) anthracene (ADN).

Referring to FIG. 1 , the relationship between the voltage and the current density of the embodiment of the present invention and the comparative example is tested. It can be seen that the organic electroluminescent device of the present invention (the light of the compound containing Inv-1 or Inv-2) can be seen under the same voltage. The layer has a higher current density than the organic electroluminescent device of the comparative example (the ADN-containing luminescent layer), especially when the voltage is above 8 volts (V).

Further, the results of measuring the turn-on voltage and current efficiency of the examples and the comparative examples at a current density of 20 mA/cm ² are as follows:

It will be apparent to those skilled in the art that various changes can be made in accordance with the embodiments of the present invention without departing from the spirit of the invention. Therefore, it is to be understood that the invention is not limited by the scope of the invention, and is intended to cover the modifications of the spirit and scope of the invention.

The first figure is a voltage versus current density diagram of an embodiment and a comparative example of the present invention.

Claims (13)

A fluorescent main illuminant material having the structure shown by the following chemical formula (I): Wherein the Ar ₁ and Ar ₂ systems are each independently a C ₆ -C ₂₀ aromatic ring. The fluorescent main illuminant material as described in claim 1 is a compound represented by the following chemical formula: The fluorescent main light-emitting material according to claim 1, wherein the fluorescent light is green fluorescent light. A fluorescent luminescent composition comprising: the luminescent main illuminant material according to any one of claims 1 to 3; and a fluorescent dopant. The composition of claim 4, wherein the fluorescent dopant is in the coordinates of Commission Internationale d'Exclairage (CIEx, y), CIEx is between 0.26 and 0.36, and CIEy is between 0.60 and 0.68. A green fluorescent dopant between the properties. The composition of claim 5, wherein the green fluorescent dopant is C545T. An organic electroluminescent device comprising a layered structure arranged in the following order: a transparent substrate, an anode layer, a hole transport layer, a light emitting layer, an electron transport layer and a cathode layer, wherein the organic motor light emitting device is characterized in that: The layer includes the fluorescent main illuminant material according to any one of claims 1 to 3. The device of claim 7, further comprising a hole injection layer. The device of claim 7, further comprising an electron injecting layer. The device of claim 7, wherein the anode layer and the cathode layer are respectively in contact with an external power source to form an electrical path. The device of claim 7, wherein the luminescent layer further comprises a fluorescent dopant. The device of claim 11, wherein the fluorescent dopant is in the coordinates of Commission Internationale d'Exclairage (CIEx, y), CIEx is between 0.26 and 0.36, and CIEy is between 0.60 and 0.68. A green fluorescent dopant with a characteristic between. The device of claim 12, wherein the green fluorescent dopant is C545T.