CN106816543A - Gold-tinted organic luminescent device and preparation method thereof - Google Patents

Abstract

The invention discloses a yellow light organic light-emitting device and a preparation method thereof, which sequentially include a substrate, an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer and a cathode, and the electron transport layer is a non- Doped Firpic ultrathin layer. The invention uses phosphorescent material for the functional layer for the first time, has simple preparation process, low cost, good device performance, high current density and high brightness, and has wide application prospect.

Description

Yellow light organic light-emitting device and preparation method thereof

technical field

The invention belongs to the technical field of semiconductor display, and relates to a yellow organic light-emitting diode based on an FIrpic ultrathin electron transport layer and a preparation method thereof.

Background technique

For a long time, the most important sensory ability that humans use to obtain information is vision. After entering the information age, with the explosive growth of digital information, people's requirements for display devices are gradually increasing. For the most concerned flat panel display device at present, from the black and white LCD electronic watch that can only display limited numbers at the beginning to the large curved high-definition display that can display gorgeous and complex images, the continuous progress of human science and technology will surely accompany The continuous development of display technology will be reflected in people's life everywhere.

The characteristics of the organic light-emitting device (OrganicLight-EmittingDevice, OLED) are very distinct. Different from the current commonly used liquid crystal display method, OLED is a spontaneous light-emitting device. After the device is applied with an appropriate voltage, the carriers will directly recombine and emit light in the light-emitting layer of the device. The long-standing problem of small viewing angle makes display screens made of OLED technology no longer need complex optical switches and backlight panels, making it possible for lighter and thinner displays to appear. Due to these advantages and characteristics, the display industry unanimously believes that OLED technology is a well-deserved leader in opening the next generation of display technology.

The luminescent materials used in OLEDs can be divided into two categories. One is fluorescent materials and the other is phosphorescent materials. According to the spin quantum statistical theory, the formation probability ratio of singlet excitons and triplet excitons after electron and hole recombination is 1:3, that is, singlet excitons only account for 25% of the "electron-hole pairs". , 75% of the "electron-hole pairs" do not contribute to "electroluminescence" due to the formation of spin-forbidden triplet excitons. Therefore, the maximum internal quantum efficiency of electroluminescence is 25% for the fluorescent luminescent material that only relies on singlet exciton radiation to decay and emit light. Phosphorescent materials can achieve phosphorescence emission in which singlet and triplet luminescence are mixed through intersystem crossing. Theoretically, the internal quantum efficiency of OLEDs made of phosphorescent materials can reach 100%, and its luminous efficiency is three times higher than that of fluorescent materials. In the late 1990s, two research groups, Professor Forrest of Princeton University and Professor Thompson of the University of Southern California, successfully used platinum-porphyrin complexes and cyclometallated iridium-phenylpyridine complexes as phosphorescent dyes with The charge-transporting host material is used to make the light-emitting layer in the organic electroluminescent device by co-evaporation, and the external quantum efficiency of the device reaches 4% and 8%, which is greatly improved compared with the electroluminescent device. In recent years, research on electrophosphorescent materials and devices based on heavy metal complexes, especially iridium complexes, has become a hotspot in the field of organic electroluminescence. Among them, the maximum external quantum efficiency has reached 19.2%, and the energy conversion efficiency is 72lm/W (65cd/m2) for the multi-layer OLED device made by using iridium complexes as phosphorescent materials.

The selection, thickness and concentration of electron transport layer materials are one of the main factors affecting the performance of organic light-emitting diodes. The selection of materials and preparation methods have a crucial impact on organic light-emitting diodes. FIrpic has the advantages of high triplet energy level, low LUMO energy level, etc., and it is easy to cause triplet annihilation in host-guest doping, because there are still complex preparation processes, complicated steps, PE (power efficiency) and CE (current efficiency) ) and the problem that the brightness cannot be taken into account at the same time.

Contents of the invention

The purpose of the present invention is to use FIrpic as an ultra-thin layer for electron transmission, improve the CE (current efficiency) and PE (power efficiency) of the device, and realize a high-performance yellow organic light-emitting diode. Therefore, a method for preparing a yellow organic light-emitting diode based on an ultra-thin electron transport layer of FIrpic is provided.

The technical solution of the present invention is: a yellow light organic light-emitting device based on FIrpic as an electron transport layer, which sequentially includes a substrate, an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer and The cathode and the electron transport layer are non-doped Firpic ultra-thin layers.

Further, the thickness of the non-doped Firpic ultra-thin layer is 0.5 nm.

Further, the light-emitting layer is composed of host material and guest light-emitting material doped.

Further, the light-emitting layer is doped with CBP and (tbt) ₂ Ir(acac).

Further, the material of the hole injection layer is MoO ₃ .

Further, the hole transport layer is composed of NPB material layer and TCTA material layer.

Further, the electron injection layer TPBi.

A method for preparing a yellow light organic light-emitting device based on FIrpic as an electron transport layer, the steps are as follows:

(1) cleaning the ITO glass substrate;

(2) On the ITO glass substrate, a hole injection layer is prepared by vacuum evaporation;

(3) preparing a hole transport layer by vacuum evaporation on the hole injection layer;

(4) Put the device processed in step (3) into an organic vacuum chamber, and wait for the pressure in the evaporation chamber to be lower than 3×10 ^-4 Pa, to Evaporation rate of , with CBP as host material and (tbt) ₂ Ir(acac) as guest luminescent material, perform mixed evaporation to prepare luminescent layer. After the thickness of luminescent layer reaches the predetermined value, then use Evaporate the FIrpic material at a certain evaporation rate to prepare the electron transport layer, and end the evaporation after the thickness of the electron transport layer reaches the predetermined value;

(5) preparing an electron injection layer by vacuum evaporation on the electron transport layer;

(6) Prepare the cathode on the electron injection layer by vacuum evaporation.

Preferably, the steps are as follows:

(1) Clean the ITO glass substrate: (a) Set the parameters of the ultrasonic instrument: temperature 30°C, time 15min, power 70w; (b) Wipe the surface of the ITO glass substrate with a dust-free cloth dipped in acetone until no trace is observed with the naked eye. Particle impurities; (c) place the cleaned ITO glass substrate on a polytetrafluoroethylene substrate, and then put it into a beaker of deionized water with detergent for the first step of ultrasonic cleaning; (d) take out Substrate frame, put into the beaker that acetone is housed again after washing with acetone and carry out second step cleaning; (e) carry out the third step ultrasonic cleaning to ITO glass substrate with deionized water, (f) take out substrate frame, After rinsing with isopropanol, put it into a beaker filled with isopropanol for the fourth step of cleaning, (g) put it in a baking oven for 20 minutes, (h) take out the dried ITO glass substrate and put it in a glass dish , and then put into the UV device for UV irradiation for 15 minutes;

(2) Preparation of the hole injection layer: put the ITO glass substrate treated in step (1) into a vacuum chamber, and use MoO3 as the material _of the hole injection layer; the pressure in the evaporation chamber is lower than 1.8×10 ^-3 Pa , start to increase the current to 20A, to The evaporation rate obtained a thickness of 5nm film;

(3) Preparation of the hole transport layer: put the ITO glass substrate treated in step (2) into a vacuum chamber, use NPB and TCTA as the material of the hole transport layer, and the pressure in the evaporation chamber is lower than 3×10 ^-4 Pa, with Evaporation rate, after the thickness reaches 40nm and 15nm respectively, end the evaporation;

(4) Preparation of light-emitting layer and electron transport layer: put the ITO glass substrate treated in step (3) into an organic vacuum chamber, and use CBP and (tbt) ₂ Ir(acac) as light-emitting layer materials for mixed evaporation , when the pressure in the evaporation chamber is lower than 3×10 ^{- 4} Pa, the The evaporation rate, after the thickness reaches 25nm and then Evaporate the FIrpic material at a certain evaporation rate, and end the evaporation after the thickness reaches 0.5nm;

(5) Preparation of electron injection layer: put the ITO glass substrate treated in step (4) into an organic vacuum chamber, use TPBi material as the electron transport layer, and wait for the vapor deposition chamber to have a pressure lower than 3×10 ^-4 Pa, by The evaporation rate is high, and the evaporation ends when the thickness reaches 35nm.

(6) Prepare the metal cathode: put the ITO glass substrate treated in step (5) into the metal vacuum deposition chamber, use Mg and Ag as the metal cathode, and wait for the pressure in the evaporation chamber to be lower than 1.8×10 ^-3 Pa. A metal thin film with a thickness of 200nm was obtained at an evaporation rate of .

In the present invention:

Firpic refers to: bis(4,6-difluorophenylpyridine-N,C2)pyridyl iridium;

CBP refers to: 4,4-bis(9-carbazole)biphenyl 4,4';

(tbt) ₂ Ir(acac) refers to: 2-(p-butyl-tert-phenyl)-benzothiazole;

TPBi refers to: 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene;

NPB refers to: N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamineN,N';

TCTA refers to: 4,4',4"-tris(carbazol-9-yl)triphenylamine 4,4',4";

Compared with the prior art, the present invention has the following advantages:

In the present invention, for the first time, the phosphorescent material FIrpic is used as a non-doped electron transport layer alone, which is of great practical significance. Using the phosphorescent material as the electron transport layer greatly improves the current density, current efficiency, power efficiency and brightness of the device. The experimental steps and production costs are greatly reduced.

Description of drawings

Fig. 1 is a schematic structural view of a yellow light organic light-emitting device of the present invention;

Figure 2 shows the device structure: glass substrate/ITO/MoO3(5nm)/NPB(40nm)/TCTA(15nm)/CBP:(tbt) ₂ Ir(acac)(25nm)/FIrpic(0.5nm)/TPBi(35nm )/Mg:Ag normalized spectrum.

Figure 3 shows the device structure: glass substrate/ITO/MoO3(5nm)/NPB(40nm)/TCTA(15 nm)/CBP:(tbt) ₂ Ir(acac)(25nm)/FIrpic(0.5nm)/TPBi( 35nm)/Mg:Ag voltage-current density curve.

Figure 4 shows the device structure: glass substrate/ITO/MoO3(5nm)/NPB(40nm)/TCTA(15nm)/CBP:(tbt) ₂ Ir(acac)(25nm)/FIrpic(0.5nm)/TPBi(35nm )/Mg:Ag current density-current efficiency diagram.

detailed description

Example 1

As shown in Figure 1, a yellow-light organic light-emitting device based on FIrpic as an electron transport layer includes a substrate, an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode in sequence. , the light-emitting layer is doped by host material and guest material, and the electron transport layer is FIrpic.

The specific structure is: glass substrate/ITO/MoO3(5nm)/NPB(40nm)/TCTA(15nm)/CBP:(tbt) ₂ Ir(acac)(25nm)/FIrpic(0.5nm)/TPBi(35nm)/ Mg:Ag.

The preparation method is:

(1) Clean the ITO glass substrate: (a) Set the parameters of the ultrasonic instrument: temperature 30°C, time 15min, power 70w; (b) Wipe the surface of the ITO glass substrate with a dust-free cloth dipped in acetone until no trace is observed with the naked eye. Particle impurities; (c) place the cleaned ITO glass substrate on a polytetrafluoroethylene substrate, and then put it into a beaker of deionized water with detergent for the first step of ultrasonic cleaning; (d) take out Substrate frame, put into the beaker that acetone is housed again after washing with acetone and carry out second step cleaning; (e) carry out the third step ultrasonic cleaning to ITO glass substrate with deionized water, (f) take out substrate frame, After rinsing with isopropanol, put it into a beaker filled with isopropanol for the fourth step of cleaning, (g) put it in a baking oven for 20 minutes, (h) take out the dried ITO glass substrate and put it in a glass dish , and then put into the UV device for UV irradiation for 15 minutes;

(2) Preparation of the hole injection layer: put the ITO glass substrate treated in step (1) into a vacuum chamber, and use MoO3 as the material _of the hole injection layer; the pressure in the evaporation chamber is lower than 1.8×10 ^-3 Pa , start to increase the current to 20A, to The evaporation rate obtained a thickness of 5nm film;

(3) Preparation of the hole transport layer: put the ITO glass substrate treated in step (2) into a vacuum chamber, use NPB and TCTA as the material of the hole transport layer, and wait for the pressure in the evaporation chamber to be lower than 3×10 ^-4 Pa, with Evaporation rate, after the thickness reaches 40nm and 15nm respectively, end the evaporation;

(4) Preparation of light-emitting layer and electron transport layer: put the ITO glass substrate treated in step (3) into an organic vacuum chamber, and use CBP and (tbt) ₂ Ir(acac) as light-emitting layer materials for mixed evaporation , when the pressure in the evaporation chamber is lower than 3×10 ^{- 4} Pa, the The evaporation rate, after the thickness reaches 25nm and then Evaporate the FIrpic material at a certain evaporation rate, and end the evaporation after the thickness reaches 0.5nm;

(5) Preparation of electron injection layer: put the ITO glass substrate treated in step (4) into an organic vacuum cavity, use TPBi material as the electron transport layer, and wait for the pressure in the evaporation chamber to be lower than 3×10 ^-4 Pa, by The evaporation rate is high, and the evaporation ends when the thickness reaches 35nm.

(6) Prepare the metal cathode: put the ITO glass substrate treated in step (5) into the metal vacuum deposition chamber, use Mg and Ag as the metal cathode, and wait for the pressure in the evaporation chamber to be lower than 1.8×10 ^-3 Pa. A metal thin film with a thickness of 200nm was obtained at an evaporation rate of .

The above-mentioned embodiments only express the specific implementation manners of the present application, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the protection scope of the present application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the technical solution of the present application, and these all belong to the protection scope of the present application.

Claims (9)

1. a yellow light organic light-emitting device based on FIrpic as electron transport layer, comprising substrate, anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer and cathode successively, it is characterized in that , the electron transport layer is a non-doped Firpic ultra-thin layer. 2. A kind of yellow light organic light-emitting device based on FIrpic as electron transport layer according to claim 1, characterized in that, the thickness of the non-doped Firpic ultra-thin layer is 0.5nm. 3. A yellow light organic light-emitting device based on FIrpic as an electron transport layer according to claim 1, wherein the light-emitting layer is formed by doping a host material and a guest light-emitting material. 4 . A yellow organic light-emitting device based on FIrpic as an electron transport layer according to claim 1 , wherein the light-emitting layer is doped with CBP and (tbt) ₂ Ir(acac). 5 . A yellow organic light-emitting device based on FIrpic as an electron transport layer according to claim 1 , wherein the material of the hole injection layer is MoO ₃ . 6. A kind of yellow light organic light-emitting device based on FIrpic as electron transport layer according to claim 1, characterized in that, the hole transport layer is composed of NPB material layer and TCTA material layer. 7. A kind of yellow light organic light-emitting device based on FIrpic as the electron transport layer according to claim 1, characterized in that the electron injection layer TPBi. 8. A kind of preparation method based on FIrpic according to claim 1 as the yellow light organic light-emitting device of electron transport layer, it is characterized in that, the steps are as follows: (1) cleaning the ITO glass substrate; (2) On the ITO glass substrate, a hole injection layer is prepared by vacuum evaporation; (3) preparing a hole transport layer by vacuum evaporation on the hole injection layer; (4) Put the device processed in step (3) into an organic vacuum chamber, and wait for the pressure in the evaporation chamber to be lower than 3×10 ^-4 Pa, to Evaporation rate of , with CBP as host material and (tbt) ₂ Ir(acac) as guest luminescent material, perform mixed evaporation to prepare luminescent layer. After the thickness of luminescent layer reaches the predetermined value, then Evaporate the FIrpic material at a certain evaporation rate to prepare the electron transport layer, and end the evaporation after the thickness of the electron transport layer reaches the predetermined value; (5) preparing an electron injection layer by vacuum evaporation on the electron transport layer; (6) Prepare the cathode on the electron injection layer by vacuum evaporation. 9. A kind of preparation method based on FIrpic as the yellow light organic light-emitting device of electron transport layer according to claim 8, it is characterized in that, the steps are as follows: (1) Clean the ITO glass substrate: (a) Set the parameters of the ultrasonic instrument: temperature 30°C, time 15min, power 70w; (b) Wipe the surface of the ITO glass substrate with a dust-free cloth dipped in acetone until no trace is observed with the naked eye. Particle impurities; (c) place the cleaned ITO glass substrate on a polytetrafluoroethylene substrate, and then put it into a beaker of deionized water with detergent for the first step of ultrasonic cleaning; (d) take out Substrate frame, put into the beaker that acetone is housed again after washing with acetone and carry out second step cleaning; (e) carry out the third step ultrasonic cleaning to ITO glass substrate with deionized water, (f) take out substrate frame, After rinsing with isopropanol, put it into a beaker filled with isopropanol for the fourth step of cleaning, (g) put it in a baking oven for 20 minutes, (h) take out the dried ITO glass substrate and put it in a glass dish , and then put into the UV device for UV irradiation for 15 minutes; (2) Preparation of the hole injection layer: put the ITO glass substrate treated in step (1) into a vacuum chamber, and use MoO3 as the material _of the hole injection layer; the pressure in the evaporation chamber is lower than 1.8×10 ^-3 Pa , start to increase the current to 20A, to The evaporation rate obtained a thickness of 5nm film; (3) Preparation of the hole transport layer: put the ITO glass substrate treated in step (2) into a vacuum chamber, use NPB and TCTA as the material of the hole transport layer, and the pressure in the evaporation chamber is lower than 3×10 ^-4 Pa, with Evaporation rate, after the thickness reaches 40nm and 15nm respectively, end the evaporation; (4) Preparation of light-emitting layer and electron transport layer: put the ITO glass substrate treated in step (3) into an organic vacuum chamber, and use CBP and (tbt) ₂ Ir(acac) as light-emitting layer materials for mixed evaporation , when the pressure in the evaporation chamber is lower than 3×10 ^-4 Pa, the The evaporation rate, after the thickness reaches 25nm and then Evaporate the FIrpic material at a certain evaporation rate, and end the evaporation after the thickness reaches 0.5nm; (5) Preparation of electron injection layer: put the ITO glass substrate treated in step (4) into an organic vacuum chamber, use TPBi material as the electron transport layer, and wait for the vapor deposition chamber to have a pressure lower than 3×10 ^-4 Pa, by Evaporation rate, when the thickness reaches 35nm to end the evaporation; (6) Prepare the metal cathode: put the ITO glass substrate treated in step (5) into the metal vacuum deposition chamber, use Mg and Ag as the metal cathode, and wait for the pressure in the evaporation chamber to be lower than 1.8×10 ^-3 Pa. A metal thin film with a thickness of 200nm was obtained at an evaporation rate of .