WO2020199770A1

WO2020199770A1 - Test method, screening method, and oled design method

Info

Publication number: WO2020199770A1
Application number: PCT/CN2020/075463
Authority: WO
Inventors: 尤娟娟; 申永奇
Original assignee: 京东方科技集团股份有限公司
Priority date: 2019-04-04
Filing date: 2020-02-17
Publication date: 2020-10-08
Also published as: CN109950413B; CN109950413A

Abstract

Provided is a test method for a doped layer. The doped layer comprises an organic material and a metal doped in the organic material. The method comprises: providing a test element, and detecting the light transmittance of the test element, the test element comprising a substrate, an organic material layer on the substrate, and a metal layer located on the organic material layer and in contact with the organic material layer. According to the test method, a doped layer can be tested in a low-cost and simple manner. Also provided are a screening method for an organic material of a doped layer and an organic light-emitting diode design method.

Description

Test method, screening method and OLED design method

This application claims the priority of the Chinese patent application No. 201910272491.8 filed on April 4, 2019, and the contents of the above-mentioned Chinese patent application are quoted here in full as a part of this application.

Technical field

The embodiments of the present disclosure relate to a testing method of a doped layer, a screening method of an electron transport type material of the doped layer, and a design method of an OLED.

Background technique

OLED (Organic Light-Emitting Diode, organic light-emitting diode) devices have attracted more and more attention because of their advantages such as self-luminescence, wide viewing angle, almost infinitely high contrast, low power consumption, and extremely high response speed. Tandem OLED (Tandem OLED, TOLED) (or tandem OLED) is an OLED device structure with high efficiency and long life, formed by superimposing multiple traditional OLED devices on each other through a connecting layer.

Summary of the invention

At least one embodiment of the present disclosure provides a method for testing a doped layer. The doped layer includes an organic material and a metal doped in the organic material. The method includes: providing a test element, and inspecting the test element The light transmittance of the test element, wherein the test element comprises: a substrate; an organic material layer on the substrate; and a metal layer on the organic material layer and in contact with the organic material layer; and

For example, according to an embodiment of the present disclosure, the method further includes: evaluating the diffusion stability of the metal material of the metal layer with respect to the organic material based on the light transmittance.

For example, according to an embodiment of the present disclosure, the providing the test element includes preparing the test element, including: providing the substrate; evaporating the organic material layer on the substrate; and depositing the organic material layer on the organic material layer The metal layer is evaporated.

For example, according to an embodiment of the present disclosure, the thickness of the metal layer is less than 50 nm.

For example, according to an embodiment of the present disclosure, the thickness of the metal layer is greater than 5 nm.

For example, according to an embodiment of the present disclosure, the metal of the metal layer includes at least one of the group consisting of Li, Mg, Ca, Cs, and Yb.

For example, according to an embodiment of the present disclosure, the organic material of the organic material layer is an electron transport type material.

For example, according to an embodiment of the present disclosure, an ultraviolet-visible spectrophotometer is used to detect the light transmittance of the test element.

For example, according to an embodiment of the present disclosure, the light transmittance includes visible light transmittance.

For example, according to an embodiment of the present disclosure, the light transmittance includes at least one of the group consisting of red light transmittance, blue light transmittance, and green light transmittance.

At least one embodiment of the present disclosure also provides a method for screening electron transport materials of a doped layer. The method includes: providing a plurality of test elements; detecting the light transmittance of the test elements; The light transmittance of each of the test elements at a specific wavelength is compared with the threshold transmittance. Each of the plurality of test elements includes: a substrate; an organic material layer on the substrate; and a metal layer on the organic material layer and in contact with the organic material layer.

For example, according to an embodiment of the present disclosure, the method further includes: when the light transmittance of the test element at the specific wavelength is greater than the threshold transmittance, retaining the organic light in the test element For the organic material of the material layer, when the light transmittance of the test element at the specific wavelength is less than the threshold transmittance, the organic material of the organic material layer in the test element is excluded.

At least one embodiment of the present disclosure further provides a method for designing an organic light emitting diode, the method including: determining an electron transport type material for implementing the organic light emitting diode according to the screening method described above.

Description of the drawings

In order to explain the technical solutions of the embodiments of the present disclosure more clearly, the following will briefly introduce the drawings that need to be used in the embodiments. It should be understood that the following drawings only show certain embodiments of the present disclosure, and therefore do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative work.

Fig. 1 shows a flow chart of a test method for a doped layer according to an embodiment of the present disclosure;

Fig. 2 shows a schematic diagram of a test element according to an embodiment of the present disclosure;

Fig. 3 shows a flow chart of preparing a test element according to an embodiment of the present disclosure;

FIG. 4 shows a schematic diagram of detecting the light transmittance of the test element shown in FIG. 2;

FIG. 5 shows a chart of example test results of the test method according to an embodiment of the present disclosure;

FIG. 6 shows a flowchart of a method for screening electron transport materials of a doped layer according to an embodiment of the present disclosure;

Figure 7 shows a schematic diagram of the structure of an example Tandem WOLED.

detailed description

Hereinafter, the testing method of the doped layer, the screening method of the electron transport type material of the doped layer and the design method of the OLED according to the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

In order to make the purpose, technical solutions and advantages of the present utility disclosure clearer, the technical solutions in the embodiments of the present disclosure will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are A part of the embodiments of the present disclosure, but not all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present disclosure.

Unless the context defines otherwise, the singular form includes the plural form. Throughout the specification, the terms "including", "having", etc. are used herein to designate the existence of the described features, numbers, steps, operations, elements, components or combinations thereof, but do not exclude the existence or addition of one or more Other features, numbers, steps, operations, elements, parts, or combinations thereof.

As an example, the TOLED structure may include a plurality of OLED units connected in series, and each OLED unit includes a complete functional layer for realizing light emission, such as a hole transport functional layer, a light emitting layer, and an electron transport functional layer. The electron transport function layer may include one or both of an electron injection layer and an electron transport layer; the hole transport function layer may include one or both of a hole injection layer and a hole transport layer. In the TOLED structure, for example, multiple OLED units share one anode and one cathode. Therefore, the TOLED structure improves efficiency and saves materials. A charge generating layer (Charge Generating Layer, CGL) is arranged between each OLED unit. The CGL may include, for example, a stacked n-doped layer and a p-doped layer. The n-doped layer may include an organic electron transport material (OETM) and a metal doped in the organic electron transport material. Due to the active characteristics of these doped metals, these metals are prone to diffuse during the lighting process or the aging process of the device, leading to an increase in the voltage of the device or the quenching of the efficiency of the adjacent light-emitting layer. Therefore, how to test and select the appropriate n-doped layer material is one of the key factors of TOLED technology.

For example, a high-contrast transmission electron microscope-X-ray energy dispersive spectroscopy (Transmission electron microscope-Energy Dispersive X ray spectroscopy, TEM-EDX) can be used to analyze device degradation. The TOLED device can be manufactured first, and then the TOLED device can be degraded. Through the cross-sectional TEM observation of the cross-section (section) of the TOLED device after the degradation treatment, combined with the EDX equipped with the TEM, various morphologies and compositions can be evaluated at the nanometer scale, so as to determine the metal atoms in the n-doped layer in the TOLED structure The diffusion range and the change of composition in the n-doped layer. However, this test method is difficult and requires high equipment. In addition, the test method requires a high level of sample preparation, which leads to high test costs.

Some embodiments according to the present disclosure provide a method for testing a doped layer, the doped layer including an organic material and a metal doped in the organic material, the method includes: providing a test element, and detecting the light transmittance of the test element Overrate. The test element includes: a substrate; an organic material layer on the substrate; and a metal layer on and in contact with the organic material layer. This method may be suitable for testing the diffusion stability of the doped metal of the n-doped layer in the CGL in the TOLED structure in the organic material, for example.

In the above embodiment, the doped layer is tested by detecting the light transmittance of the test element. Therefore, the test process does not require the preparation of complex devices, nor does it require expensive equipment and complex operations. It can be low-cost and simple. Ground the doped layer for testing.

However, the test method according to the embodiments of the present disclosure is not limited to the n-doped layer used in TOLEDs, and can also be used for testing doped layers in other applications or devices. The doped layers include organic materials and in organic materials. Doped metal.

Fick's law is a law that describes the relationship between mass transfer flux and concentration gradient in the process of molecular diffusion without relying on the mass transfer phenomenon that occurs through macroscopic mixing. According to Fick's law, the diffusion distance of doped metal in organic materials can be expressed by the following formula.

Among them, L represents the diffusion distance, D represents the diffusion coefficient, and τ represents the diffusion time. Here, D is related to the microstructure of the material itself.

On the one hand, the smaller the D, the stronger the bond between the organic material and the metal atom, the shorter the diffusion distance of the doped metal in the organic material, and the deterioration resistance of the n-doped layer including the doped metal and organic material The better.

On the other hand, the smaller the D, the smaller the probability of collision between metal atoms deposited on the organic material, the smaller the degree of metal agglomeration, and the greater the light transmittance of the metal thin film deposited on the organic material.

Therefore, by testing, for example, the light transmittance of a laminate composed of an organic material and a (predetermined thickness) metal thin film deposited on the organic material, the bonding ability of the metal atom and the organic material can be judged, and the metal atom can be judged in the organic material. The diffusion stability of the metal and the organic material is further judged for the anti-deterioration performance of the n-doped layer.

FIG. 1 shows a test method for a doped layer (for example, an n-doped layer) according to at least one embodiment of the present disclosure, wherein the n-doped layer includes an organic material and a metal doped in the organic material.

As shown in FIG. 1, in this embodiment, the testing method of the n-doped layer includes:

S110: Provide test components; and

S120: Detect the light transmittance of the test element.

In addition, as shown in FIG. 1, the testing method of the n-doped layer may further include:

S130: Evaluate the diffusion stability of the metal of the metal layer to the organic material based on the light transmittance.

In this embodiment, for example, it is possible to obtain different test elements by changing only one parameter for preparing the test element and fixing other parameters. The parameters for preparing the test element may include the type of organic material, the layer thickness of the organic material, the type of doped metal, the layer thickness of doped metal, etc., as described in detail below.

For these test elements, the greater the light transmittance, the higher the diffusion stability of the n-doped layer corresponding to the test element, so that the n-doped layer that is more suitable for a certain application or device can be selected from these test elements.

For example, the performance of the first organic material and the second organic material as the organic material in the n-doped layer can be compared by comparing the light transmittance of the test element of the first test element and the second test element, wherein the first The test element has a metal layer including a metal material for doping and a first organic material layer including a first organic material, and the second test element has the metal layer and a second organic material layer including a second organic material. Under the same test conditions, the greater the light transmittance of the test element corresponding to the organic material, the better the performance of the organic material as the organic material in the n-doped layer when the metal material is used as the doped metal. For example, when the light transmittance of the second test element is greater than the light transmittance of the first test element, compared to the first organic material, the second organic material has better performance as the organic material in the n-doped layer. it is good.

FIG. 2 shows a schematic diagram of a test element 100 according to an embodiment of the present disclosure. As shown in FIG. 2, the test element 100 includes a substrate 110, an organic material layer 120 on the substrate 110, and a metal layer 130 on the organic material layer 120 and in contact with the organic material layer 120.

The combination performance of the metal material of the metal layer 130 and the organic material of the organic material layer 120 can be evaluated by detecting the light transmittance of the test element 100, thereby evaluating the diffusion stability of the metal material of the metal layer 130 to the organic material of the organic material layer 120 .

In some embodiments, providing the test element 100 includes preparing the test element 100. FIG. 3 shows a flow chart of preparing the test element 100 according to an embodiment of the present disclosure.

As shown in FIG. 3, preparing the test element 100 includes:

S111: Provide base 110;

S112: evaporate an organic material layer 120 on the substrate 110; and

S113: The metal layer 130 is vapor-deposited on the organic material layer.

In order to prepare the CGL, the organic material layer 120 and the metal layer 130 are usually deposited by evaporation. Therefore, the organic material layer 120 and the metal layer 130 are formed by the evaporation method to reliably test the performance of the n-doped layer in the CGL. . In addition, the cost of the evaporation method is low.

In other embodiments, other methods may be used to form the organic material layer or the metal layer 130, such as wet coating (for example, by chemical reagents), chemical vapor deposition, physical vapor deposition other than evaporation (for example, Sputtering coating) etc.

For example, the substrate is a sheet, for example, it may be made of transparent materials such as glass, quartz, plastic, etc., for example, made of transparent optical glass. The thickness of the substrate can be selected according to the required strength and transparency.

For example, the organic material layer 120 may be an electron transport type material, such as TPBI, Alq3, Almq3, DVPBi, BPhen, TAZ, OXD, PBD, BND, PV, B3PyPB, etc.

For the aforementioned organic material layer 120, for example, the metal used for doping may include one or more of Li, Mg, Ca, Cs, Yb, and the like.

For the aforementioned metals, for example, the thickness of the metal layer 130 may be less than 50 nm. The thickness of the metal layer 130 is less than 50 nm to ensure the transmission characteristics of the test element 100 while avoiding the reflection characteristics of the test element 100.

For another example, the thickness of the metal layer 130 may be greater than 5 nm. The thickness of the metal layer 130 greater than 5 nm is beneficial to ensure that the metal layer 130 is complete and uniform.

For example, the thickness of the metal layer 130 may be 5 nm to 50 nm, for example, it may be 10 nm to 40 nm, and for example, it may be 15 nm to 25 nm.

In some embodiments, an ultraviolet-visible spectrophotometer can be used to detect the light transmittance of the test element 100. The ultraviolet-visible spectrophotometer can detect the light transmittance of the test element 100 with light of a specific wavelength within a certain range, for example. In other embodiments, other light transmittance testers can be used to test the light transmittance of the test element 100.

FIG. 4 shows a schematic diagram of detecting the light transmittance of the test element 100 shown in FIG. 2. As shown in FIG. 4, the light transmittance of the test element 100 can be tested by a test instrument such as an ultraviolet-visible spectrophotometer. In one example, the test instrument includes a light source 220, a light detector 230, and an optical assembly 240. The light source 220 may be, for example, a tungsten lamp or a tritium lamp, which emits a detection beam 210. The light beam 210 is adjusted to have a specific direction and a specific wavelength or a specific wavelength range through the optical assembly 240, and then irradiates the test element 100 from the side where the substrate 110 of the test element 100 is located. The light detector 230 collects the light beam 210 passing through the test element 110 on the other side of the test element 100 to detect the transmittance of the light beam 210 adjusted to have a specific wavelength or a specific wavelength range to the test element 110. The optical component 240 may include at least one of a lens (concave lens or convex lens), a mirror, an optical waveguide, and the like.

It should be noted that the test element 100 can also be irradiated from the opposite side of the substrate 110 of the test element 100, and the light beam 210 passing through the test element 100 can be collected on the other side of the test element 100 to detect that the light beam 210 affects the test element. The present disclosure is not limited to the transmittance of 110, as long as the light transmittance of the test element 100 can be measured.

For example, the light detector 230 may include an array of photosensors, and these photosensors may include photodiodes, phototransistors, etc., which may be used to detect light in a spectral range from ultraviolet light to visible light, for example.

In some embodiments, the light transmittance may include visible light transmittance, and the corresponding wavelength range of visible light may be 380 nm-780 nm.

In some embodiments, the light transmittance may include at least one of the group consisting of red light transmittance, blue light transmittance, and green light transmittance.

In applications such as OLED display devices, the corresponding light transmittance of the visible light detection test element 100 can also be used to obtain the visible light transmission performance of the corresponding n-doped layer. The better the visible light transmission performance of the n-doped layer, the n-doped layer The better the performance of the layer used for CGL in OLED.

In applications such as WOLED (White OLED) display devices, the red light transmittance, blue light transmittance and green light transmittance of the test element 100 can be detected. The red light transmittance, blue light transmittance, and green light transmittance can be used to evaluate the diffusion stability of the metal material of the metal layer 130 to the organic material layer 120. In addition, the test element 100 has a large light transmittance for red, blue, and green light, which can also indicate that the n-doped layer corresponding to the test element 100 has good light transmittance for red, blue, and green light. The n-doped layer is suitable for applications in WOLED display devices.

FIG. 5 shows a graph of example test results of the test method according to an embodiment of the present disclosure.

In this embodiment, a reference test element having an organic material layer including a reference OETM and a Li metal layer and a new test element having an organic material layer including a new OETM and a Li metal layer are provided, wherein the reference test element and the new test element The thickness and formation parameters of the organic material layer and the metal layer are the same. Use an ultraviolet-visible spectrophotometer to detect the light transmittance of the reference test element and the new test element.

In addition, in this embodiment, a reference device including the reference OETM and doped Li metal, and a new device including the new OETM and doped Li metal are prepared. In one example, the reference OETM is BPhen, and the new OETM is B3PyPB. The reference device and the new device are subjected to the same degradation treatment, and the lifetime of the device and the driving voltage difference before and after the degradation treatment are measured. Here, the lifetime of the device is the time required when the external quantum efficiency (EQE) of the device drops to 95%.

As shown in FIG. 5, in this example, the reference test element including the reference OETM is transparent to blue light (for example, a wavelength of 450 nm), green light (for example, a wavelength of 550 nm), and red light (for example, a wavelength of 650 nm). The overrates were 65%, 60% and 45% respectively. The light transmittance of the new test element including the new OETM to the blue light, the green light and the red light is 78%, 75% and 65%, respectively. The new test element has higher light transmittance for blue, green and red light than the reference test element.

Correspondingly, the voltage difference, lifetime, and EQE of the reference device are 0.4V, 120hrs, and 11.2%, respectively. The voltage, lifetime and EQE of the new device are 0.25V, 150hrs and 11.5% respectively. The EQE of the reference device and the new device are not much different. However, the new device has a smaller voltage difference before and after the degradation treatment than the reference device and has a longer life span, indicating that the new device has better degradation resistance than the reference device.

It can be seen that the light transmittance of the test element including the OETM has a positive correlation with the degradation resistance of the corresponding device including the OETM.

FIG. 6 shows a flowchart of a screening method of electron transport materials of an n-doped layer according to an embodiment of the present disclosure.

As shown in Figure 6, in this embodiment, the method includes:

S210: Provide multiple test components;

S220: Detect the light transmittance of the test element; and

S230: Compare the light transmittance of each of the plurality of test elements at a specific wavelength with the threshold transmittance.

In at least one embodiment, the method may further include:

S231: When the light transmittance of the test element at a specific wavelength is greater than the threshold, retain the organic material of the organic material layer of the test element; and

S232: When the light transmittance of the test element at a specific wavelength is less than the threshold transmittance, the organic material of the organic material layer of the test element is excluded.

Similar to the test element shown in FIG. 2, each of the plurality of test elements includes a substrate, a layer of organic material on the substrate, and a metal layer on and in contact with the organic material layer.

As mentioned above, the greater the light transmittance, the higher the diffusion stability of the n-doped layer corresponding to the test element. It can be determined to exclude or retain the organic material as an n-doped layer by comparing the light transmittance and the threshold light transmittance of a test element having a metal layer including a doped metal material and an organic material layer including an organic material. Organic materials, such as organic electron transport materials.

Specifically, the greater the light transmittance of the test element corresponding to the organic material, the better the performance of the organic material as an electron transport material in the n-doped layer when the metal is used as the doped metal. Since the difference in properties of various doped metals is usually small, in some cases, it can be considered that the organic material has better performance as an electron transport type material in the n-doped layer. Therefore, the aforementioned screening method can be used to screen the electron-transporting material in the n-doped layer. The screening method does not require the production of complex devices, has low requirements on instruments and equipment, saves screening costs and time, and is beneficial to realize large-throughput screening. The threshold light transmittance can be selected as required.

Some embodiments of the present disclosure also provide a method for designing an OLED, which includes determining an electron transport type material to be used for realizing the OLED according to the screening method described above.

For example, the OLED used for implementation may be a Tandem WOLED structure. The use of WOLED+color filters to achieve color light emission has low requirements on the fine masks used in the preparation of OELDs, and is particularly advantageous for high-resolution display products. The Tandem WOLED structure is conducive to achieving high efficiency and long life. However, it should be noted that the embodiments of the present disclosure are not limited to the above-mentioned WOLED+color filter case, and can also be applied to other cases where CGL is required, such as the case of separately prepared WOLED.

Fig. 7 shows an example of a Tandem WOLED structure. For example, the WOLED can be used in a display device. As shown in FIG. 7, the WOLED includes an anode layer 310, a cathode layer 350, a first sub OLED unit 320 and a second sub OLED unit 340 between the anode layer 310 and the cathode layer 350, and a first sub OLED unit 320 and a second sub OLED unit. CGL 330 between the two sub-OLED units 340, and color filters.

The first sub-OLED unit 320 includes a first hole transport layer 321, a first electron transport layer 323, and a first organic light emitting layer 322 located between the first hole transport layer 321 and the first electron transport layer 323.

The second sub-OLED unit 340 includes a second hole transport layer 341, a second electron transport layer 343, and a second organic light emitting layer 342 located between the second hole transport layer 341 and the second electron transport layer 343.

The organic light-emitting layers 322 and 342 can work together to generate white light when current flows. The color filters include a red color filter 361, a green color filter 362, and a blue color filter 363, which can filter the white light generated by the organic light emitting layers 322 and 342 to respectively generate red light, Green and blue light. The CGL 330 includes an n-doped layer 332 and a p-doped layer 331.

For example, the test method described above can be used to test the n-doped layer 332. For example, the screening method described above can be used to screen the electron transport type material for the n-doped layer 332. For example, the design method described above can be used to design the WOLED to obtain corresponding material parameters, and then the WOLED can be prepared according to the obtained material parameters.

Some embodiments of the present disclosure also provide an OLED device prepared based on the design method described above. The OLED device includes at least one OLED device, for example, the structure of WOLED or WOLED+color filter as described above, for example The OLED device can be a display device, so as to be realized as a display panel, a mobile phone, a tablet computer, a television, a monitor, a notebook computer, a digital photo frame, a navigator, and other products or components with display functions.

The scope of the present disclosure is not limited by the above-described embodiments, but by the appended claims and their equivalent scope.

Claims

A test method for a doped layer, the doped layer includes an organic material and a metal doped in the organic material, the method includes:

Provide test components, which include:

Base

An organic material layer on the substrate; and

A metal layer on and in contact with the organic material layer; and

The light transmittance of the test element is detected.
The method according to claim 1, further comprising:

The diffusion stability of the metal material of the metal layer to the organic material is evaluated based on the light transmittance.
The method according to any one of claims 1-2, wherein:

The providing the test element includes preparing the test element, including:

Provide the substrate;

Evaporating the organic material layer on the substrate; and

The metal layer is vapor-deposited on the organic material layer.
The method according to any one of claims 1-3, wherein:

The thickness of the metal layer is less than 50 nm.
The method of claim 4, wherein:

The thickness of the metal layer is greater than 5 nm.
The method according to any one of claims 1-5, wherein:

The metal of the metal layer includes at least one of the group consisting of Li, Mg, Ca, Cs, and Yb.
The method according to any one of claims 1-6, wherein:

The organic material of the organic material layer is an electron transport type material.
The method according to any one of claims 1-7, wherein:

An ultraviolet visible spectrophotometer is used to detect the light transmittance of the test element.
The method according to any one of claims 1-8, wherein:

The light transmittance includes visible light transmittance.
The method according to any one of claims 1-9, wherein:

The light transmittance includes at least one of the group consisting of red light transmittance, blue light transmittance, and green light transmittance.
A method for screening organic materials of a doped layer, the method comprising:

A plurality of test elements are provided, each of the plurality of test elements includes:

Base

An organic material layer on the substrate; and

A metal layer on the organic material layer and in contact with the organic material layer;

Detecting the light transmittance of the plurality of test elements; and

The light transmittance of each test element of the plurality of test elements at a specific wavelength is compared with a threshold transmittance.
The screening method according to claim 11, further comprising:

When the light transmittance of the test element at the specific wavelength is greater than the threshold transmittance, the organic material of the organic material layer in the test element is retained,

When the light transmittance of the test element at the specific wavelength is less than the threshold transmittance, the organic material of the organic material layer in the test element is excluded.
A method for designing an organic light emitting diode, the method comprising:

According to the screening method of claim 11 or 12, an electron transport type material is determined to be used for realizing an organic light emitting diode.