TWI651302B - Hole-only device based on semiconductor diodes asymmetric organic hole transporting material - Google Patents

Abstract

The present invention relates to a hole-only semiconductor diode device based on an asymmetric organic hole transporting material, comprising an anode, a cathode, and an organic layer, the organic layer being an electron blocking layer, a hole transporting layer, and a hole injecting layer One or more layers, the organic layer having the compound of the formula (I), wherein R ₁ and R ₂ are each independently selected from the group consisting of hydrogen, an alkyl group having 1 to 8 carbon atoms, and 2 to 8 An olefinic group of a carbon atom, an alkynyl group having 2 to 8 carbon atoms, or an aromatic group having 5 to 20 carbon atoms. Experiments have shown that the compound of the formula (I) of the present invention has a high glass transition temperature and high thermal stability, and the prepared hole-only organic semiconductor diode device has good and stable performance and long device life.

Description

Hole-only semiconductor diode device based on asymmetric organic hole transport material

The present invention relates to novel hole-only semiconductor diode devices, and more particularly to a hole-only semiconductor diode device based on an asymmetric organic hole transport material.

The hole-only organic semiconductor diode device is a type of single carrier device used as a switch or rectifier for a smart digital power integrated circuit as a semiconductor device. The hole transporting material of the present invention is also applicable to organic electroluminescent devices (OLEDs) and field effect transistors.

Hole-only organic semiconductor diode devices generally employ a "sandwich sandwich" structure comprising an anode, a hole transport layer and a cathode. It is also possible to add a level matching hole injection layer between the anode and the hole transport layer, or to add an electron blocking layer between the hole transport layer and the cathode to further improve device performance. When the driving voltage reaches the turn-on voltage ( _Von ), holes generated by the anode are transported through the hole transport layer to the cathode, and electrons cannot enter the transport layer due to the presence of the electron blocking layer. The hole transporting material in the hole-only organic semiconductor diode device can also be applied to other semiconductor devices such as organic electroluminescent devices (OLEDs). Organic electroluminescent devices have broad market prospects. It is particularly important to develop efficient and stable organic hole transport materials for the application and promotion of organic electroluminescent devices, and it is also an urgent demand in the flat display market.

The hole transport material NPB, which is widely used at present, is as follows. In terms of photoelectric properties, it basically meets the requirements of the organic electroluminescent panel market, but its glass transition temperature (T _g ) is low, only 98 ° C. . The NPB symmetrical molecular structure tends to be regularly stacked and easy to crystallize. Once the hole transporting material is crystallized, the carrier migration mechanism in the device is changed, the transmission is unbalanced, and the stability and life of the device are adversely affected. The degree of difficulty in converting the organic layer material from amorphous to crystalline is mainly related to the glass transition temperature (T _g ) of the material. The higher the glass transition temperature, the more uniform the film formed during vacuum evaporation and the stability. The better. Therefore, it is important to develop a novel hole transporting material having a high glass transition temperature.

In view of the defects of the above materials, the present invention provides a hole-only semiconductor diode device based on an asymmetric organic hole transport material, which has high morphological stability.

A hole-only semiconductor diode device based on an asymmetric organic hole transport material, comprising an anode, a cathode, and an organic layer, the organic layer being a layer of an electron blocking layer, a hole transport layer, a hole injection layer or a plurality of layers, the organic layer having a compound of formula (I),

Wherein R ₁ and R ₂ are each independently represented by hydrogen, an alkyl group having 1 to 8 carbon atoms, an olefinic group having 2 to 8 carbon atoms, an alkyne group having 2 to 8 carbon atoms, or An aromatic group having 5 to 20 carbon atoms.

Preferably, wherein R ₁ and R ₂ are each independently represented by hydrogen, an alkyl group having 1 to 4 carbon atoms, an olefinic group having 2 to 4 carbon atoms, and an acetylene group having 2 to 4 carbon atoms. Or an aromatic group having 5 to 10 carbon atoms.

Preferably, R ₁ and R ₂ are each independently represented by hydrogen, an alkyl group having 1 to 4 carbon atoms, a phenyl group, a naphthyl group, a phenyl group or a naphthyl group having an alkyl group substituted by 1 to 4 carbon atoms.

Preferably, R ₁ is the same as R ₂ .

Preferably, wherein R ₁ and R _{2 are} preferably represented by hydrogen, phenyl or isobutyl.

The compound of formula (I) is the following structural compound:

The organic layer is an electron blocking layer, a hole transporting layer, and a hole injecting layer, and the compound of the formula (I) is located in the hole transporting layer.

The total thickness of the organic layer of the device in the present invention is from 1 to 1000 nm, preferably from 1 to 500 nm, more preferably from 10 to 300 nm.

The organic layer can be prepared by a vaporization or solution method.

The preparation method of the above organic hole material adopts the following steps: (1) under the protection of nitrogen, the intermediate Cz- is synthesized by palladium-catalyzed carbon-nitrogen coupling reaction using carbazole compound Cz and brominated spiro sulfonium SF-Br as raw materials. SF, the catalytic system is Pd ₂ (dba) ₃ /P(t-Bu) ₃ /t-BuONa, the solvent is toluene, reacting at 90-150 ° C for 10-30h; (2) using NBS as brominating agent , the synthesis intermediate Cz-SF-Br, reacted at 0-50 ° C for 10-30h; (3) through the coupling between Cz-SF-Br and dipinacol diboron (B ₂ Pin ₂ ) The synthesis reaction intermediate Cz-SF-B, the catalytic system is Pd(dppf)Cl ₂ /CH ₃ COOK, the solvent is dioxane, and the reaction is carried out at 60-120 ° C for 10-30 h; (4) Finally, The target product can be obtained by Suzuki coupling reaction of Cz-SF-B with TPA-Br. The catalyst used in this step is Pd(PPh ₃ ) ₄ , the solvent is tetrahydrofuran, and the reaction is carried out at 80-120 ° C for 10-30 h.

As mentioned above, the compounds of formula (I) in the present invention are as follows, but are not limited to the structures listed:

Experiments have shown that since the organic hole transporting material of the present invention contains key building blocks such as triarylamine, carbazole and snail, has high glass transition temperature and high thermal stability, the hole-only organic semiconductor diode of the present invention The device performs well and is stable with long device life.

10‧‧‧ glass substrate

20‧‧‧Anode

30‧‧‧ hole injection layer

40‧‧‧ hole transport layer

50‧‧‧Electronic barrier

60‧‧‧ cathode

1 is a DSC curve of Compound 1; and FIG. 2 is a structural view of the device of the present invention, wherein 10 represents a glass substrate, 20 represents an anode, 30 represents a hole injection layer, 40 represents a hole transport layer, and 50 represents a hole transport layer. The electron blocking layer, 60 represents the cathode.

In order to describe the present invention in more detail, the following examples are given, but are not limited thereto.

Example 1

Synthesis of compound c

Under nitrogen, carbazole (15.0 g, 89.7 mmol), 2-bromospiropurine (32 g, 81.0 mmol), Pd ₂ (dba) ₃ (2.2 g, 2.4 mmol) and sodium t-butoxide (10.4 g, 108.0) Mm) added to the three-neck bottle. Vacuum was applied and nitrogen gas was introduced and it was repeated three times. Subsequently, a toluene solution of tri-tert-butylphosphine (2.16 g, 50 w%) and anhydrous toluene (100 mL) were added to the above reaction flask. The temperature was raised to reflux at 110 ° C and the reaction was carried out for 12 h. After cooling to room temperature, toluene was evaporated under reduced pressure, and the residue was crystallized from ethanol to yield 39.0 g of white solid. _{^{1 H NMR (400MHz, CDCl 3}} ) δ 8.05-8.02 (m, 3H), 7.90 (d, J = 7.6Hz, 1H), 7.78 (d, J = 7.6Hz, 2H), 7.56 (dd, J = 8.0 , 2.0 Hz, 1H), 7.41 (t, J = 7.6 Hz, 1H), 7.34 (t, J = 7.6 Hz, 2H), 7.29-7.12 (m, 9H), 6.90 (d, J = 1.6 Hz, 1H) ), 6.85 (d, J = 7.6 Hz, 2H), 6.79 (d, J = 7.6 Hz, 1H).

Synthesis of compound d

Compound c (15.0 g, 31.1 mmol) was dissolved in dichloromethane (100 mL). NBS (5.5 g, 30.9 mmol) was added portionwise to the above solution and allowed to react at room temperature (20 ° C) for 12 h. The reaction solution was poured into water, and the organic layer was dried over sodium sulfate. After distilling off the solvent under reduced pressure, the residue was crystallised from ethanol to yield 15.6 g of white solid. ¹ H NMR (400 MHz, CDCl ₃ ) δ 8.14 (d, J = 1.6 Hz, 1H), 8.04 (d, J = 7.6 Hz, 1H), 7.99 (d, J = 7.6 Hz, 1H), 7.92 (d, J = 7.6 Hz, 1H), 7.80 (d, J = 7.6 Hz, 2H), 7.53 (dd, J = 8.0, 1.6 Hz, 1H), 7.44 (t, J = 7.2 Hz, 1H), 7.39-7.34 ( m, 3H), 7.30 (d, J = 8.4 Hz, 1H), 7.23 - 7.14 (m, 5H), 7.04 (d, J = 8.8 Hz, 1H), 6.86-6.80 (m, 4H).

Synthesis of compound e

Compound d (15.0 g, 26.8 mmol), dipinacol diboron (7.5 g, 29.5 mmol), Pd ₂ (dppf) Cl ₂ (2.2 g, 3.0 mmol) and CH ₃ COOK (5.2) g, 53.0 mmol) was added to a three-neck bottle. Vacuum was applied and nitrogen gas was introduced and it was repeated three times. Subsequently, dioxane (100 mL) was added to the above reaction flask, and the mixture was heated to 80 ° C for 12 h. After cooling to room temperature, the solvent was evaporated under reduced pressure. _{^{1 H NMR (400MHz, CDCl 3}} ) δ 8.54 (s, 1H), 8.07 (d, J = 7.6Hz, 1H), 8.04 (d, J = 8.0Hz, 1H), 7.91 (d, J = 7.6Hz, 1H), 7.78 (d, J = 7.6 Hz, 2H), 7.72 (d, J = 8.4 Hz, 1H), 7.56 (dd, J = 8.0, 1.6 Hz, 1H), 7.42 (t, J = 7.6 Hz, 1H), 7.35 (t, J = 7.6 Hz, 2H), 7.31 - 7.12 (m, 7H), 6.88 (d, J = 1.6 Hz, 1H), 6.85 (d, J = 7.6 Hz, 2H), 6.80 ( d, J = 7.6 Hz, 1H), 1.37 (s, 12H).

Synthesis of Compound 1

Compound e (1.6 g, 2.7 mmol), compound f (1.5 g, 2.7 mmol) (compound f with reference to US 20130112948) and Pd(PPh) ₄ (150 mg, 0.13 mmol) were added to a three-necked flask under nitrogen. Vacuum was applied and nitrogen gas was introduced and it was repeated three times. Subsequently, tetrahydrofuran (30 mL) and an aqueous potassium carbonate solution (2M, 5 mL) were placed in the above-mentioned reaction flask. The temperature was raised to reflux and the reaction was carried out for 15 h. After cooling to room temperature, the reaction solution was added to water, and the mixture was extracted with dichloromethane, and the organic phase was combined. After distilling off the solvent under reduced pressure, the residue was purified by column chromatography to yield white crystals (yield: 62%). _{^{1 H NMR (400MHz, CDCl 3}} ) δ 8.15 (s, 1H), 8.07-8.04 (m, 2H), 7.92 (d, J = 7.6Hz, 1H), 7.80 (d, J = 7.6Hz, 2H), 7.76-7.74 (m, 3H), 7.70 (d, J = 8.0 Hz, 1H), 7.58 (dd, J = 8.0, 2.0 Hz, 1H), 7.45-7.28 (m, 10H), 7.23 - 7.11 (m, 10H), 7.06-6.98 (m, 6H), 6.92-6.80 (m, 7H), 6.67 (d, J = 7.6 Hz, 1H), 6.61 (s, 1H). MS (m/z): 962 (M ⁺ ). Glass transition temperature: 193 °C.

Example 2

Glass transition temperature test: The glass transition temperature of Compound 1 was tested by differential scanning calorimetry (DSC) at a heating and cooling rate of 20 ° C/min under nitrogen atmosphere. The glass transition temperature T _g of Compound 1 was measured to be 193 ° C ( FIG. 1 ). The glass transition temperature of NPB reported in the literature is only 98 °C.

It can be seen that the compound of the present invention has a higher glass transition temperature than the conventional hole transporting material NPB, and the present invention remarkably improves the thermal stability of the hole transporting material.

Example 3

Preparation of only hole-blocking organic semiconductor diode device 1

The device structure is shown in Figure 2. The device preparation method is described as follows: First, the transparent conductive ITO glass substrate (including 10 and 20) was treated as follows: previously washed with a detergent solution, deionized water, ethanol, acetone, deionized water, and then subjected to oxygen plasma treatment for 30 seconds.

Then, 10 nm thick MoO ₃ was vapor-deposited on the ITO as the hole injection layer 30.

Then, a compound 1 having a thickness of 120 nm was vapor-deposited on the hole injection layer as the hole transport layer 40.

Then, 10 nm thick MoO ₃ was vapor-deposited on the hole transport layer as the electron blocking layer 50.

Finally, 100 nm thick aluminum was vaporized on the electron blocking layer as the device cathode 60.

The relationship between the current density of the space charge limited current (SCLC) and the electric field strength is tested by the space-limited current method as shown in equation (1):

Where J is the current density (mA cm ^-2 ), ε is the relative dielectric constant (organic material usually takes 3), and ε ₀ is the vacuum dielectric constant (8.85 × 10 ^-14 CV ^-1 cm ^-1 ), E is the electric field strength (V cm ^-1 ), L is the thickness (cm) of the sample in the device, μ ₀ is the charge mobility under the electric field (cm ² V ^-1 s ^-1 ), and β is the Poole-Frenkel factor. Indicates how quickly the mobility changes with the strength of the electric field.

Comparative example

Preparation of only hole organic semiconductor diode device 2

The method was the same as in Example 3 except that the commonly used commercially available compound NPB was used as the hole transport layer 40, and a hole-only organic semiconductor diode device for comparison was produced.

The device has a hole mobility (cm ² V ^-1 s ^-1 )

Therefore, the material of the present invention exhibits a hole mobility similar to that of NPB, but its thermal stability is better, and it is more in line with the requirements of a high-performance organic semiconductor device for a hole transporting material.

Claims (10)

A hole-only semiconductor diode device based on an asymmetric organic hole transport material, comprising an anode, a cathode, and an organic layer, the organic layer being a layer of an electron blocking layer, a hole transport layer, a hole injection layer or a plurality of layers, the organic layer having a compound of formula (I), Wherein R ₁ and R ₂ are each independently represented by hydrogen, an alkyl group having 1 to 8 carbon atoms, or an aromatic group having 5 to 20 carbon atoms. The hole-only semiconductor diode device according to claim 1, wherein R ₁ and R ₂ are each independently represented by hydrogen, an alkyl group having 1 to 4 carbon atoms, or 5 to 10 An aromatic group of a carbon atom. The hole-only semiconductor diode device according to claim 1, wherein R ₁ and R ₂ are each independently represented by hydrogen, an alkyl group having 1 to 4 carbon atoms, a phenyl group, a naphthyl group, A phenyl or naphthyl group having an alkyl group substituted with 1 to 4 carbon atoms. The hole-only semiconductor diode device according to claim 3, wherein R ₁ is the same as R ₂ . The hole-only semiconductor diode device according to claim 4, wherein R ₁ and R _{2 are} represented by hydrogen, phenyl or isobutyl. The hole-only semiconductor diode device according to claim 5, wherein the organic layer is a compound having the following structure: The hole-only semiconductor diode device according to claim 6, wherein the organic layer is a compound having the following structure: The hole-only semiconductor diode device according to claim 1, wherein the organic layer is an electron blocking layer, a hole transporting layer, and a hole injecting layer, and the compound of the formula (I) Located in the hole transport layer. The hole-only semiconductor diode device according to claim 1, wherein the organic layer has a total thickness of from 1 to 1000 nm. The hole-only semiconductor diode device according to claim 1, wherein the organic layer can be prepared by a vapor deposition or solution method.