Apparatus and method for evaluating light stability of material for organic layer of organic light emitting element

Abstract

The apparatus for evaluating the photostability of a material for an organic material layer of an organic light emitting device according to one embodiment of the present application includes a photostability chamber provided with at least four light source zones, and the at least four light source zones include: a first light source zone provided with a daylight light source; a second light source zone provided with a white fluorescent light source; a third light source zone provided with a UV cut-off light source; and a fourth light source zone to which no light is irradiated.

Description

Technical Field

[0001] This application claims priority and benefit to Korean Patent Application No. 10-2020-0168430, filed with the Korean Intellectual Property Office on December 4, 2020, the entire contents of which are incorporated herein by reference.

[0002] This application relates to apparatus and methods for evaluating the photostability of materials used in organic material layers of organic light-emitting devices. Background Technology

[0003] Organic light-emitting devices (OLEDs) are light-emitting devices that utilize organic semiconductor materials and require the exchange of holes and / or electrons between electrodes and the organic semiconductor material. Based on their operating principles, OLEDs can be mainly classified into two types. The first type involves excitons formed in the organic material layer by photons introduced from an external light source. These excitons are split into electrons and holes, which are then transported to different electrodes and used as current (voltage) sources. The second type involves injecting holes and / or electrons into the organic semiconductor material layer that forms the interface with the electrodes by applying a voltage or current to two or more electrodes, and the OLED operates using the injected electrons and holes.

[0004] Organic light emission (OLED) generally refers to the phenomenon of converting electrical energy into light energy using organic materials. Organic light-emitting devices (OLEDs) utilizing OLEDs typically have a structure comprising an anode, a cathode, and an organic material layer between them. In this paper, the organic material layer is often formed as a multilayer structure of different materials to improve the efficiency and stability of the OLED. For example, the organic material layer can be formed from a hole injection layer, a hole transport layer, a light-emitting layer, an electron blocking layer, an electron transport layer, and an electron injection layer. When a voltage is applied between the two electrodes in such an OLED structure, holes and electrons are injected from the anode and cathode, respectively, into the organic material layer. When the injected holes and electrons meet, excitons are formed, and light is emitted when these excitons return to the ground state. Such OLEDs are known to possess characteristics such as self-emission, high brightness, high efficiency, low driving voltage, wide viewing angle, and high contrast.

[0005] Based on their function, materials used as organic material layers in organic light-emitting devices can be divided into luminescent materials and charge transport materials, such as hole injection materials, hole transport materials, electron blocking materials, electron transport materials, and electron injection materials. Based on their emission color, luminescent materials include materials that emit blue light, green light, and red light, as well as materials that emit yellow light and orange light for better natural color. Summary of the Invention

[0006] Technical issues

[0007] This application aims to provide an apparatus and method for evaluating the photostability of materials used in organic material layers of organic light-emitting devices.

[0008] Technical solution

[0009] One embodiment of this application provides:

[0010] An apparatus for evaluating the photostability of materials used in organic material layers of organic light-emitting devices, the apparatus comprising a photostability chamber having at least four light source regions.

[0011] The at least four light source areas include: a first light source area equipped with a daylight source; a second light source area equipped with a white fluorescent source; a third light source area equipped with a UV cutoff source; and a fourth light source area to which no light is irradiated.

[0012] Another embodiment of this application provides:

[0013] A method for evaluating the photostability of materials used in organic material layers of organic light-emitting devices, the method comprising:

[0014] Prepare an apparatus for evaluating the photostability of materials used in organic material layers of organic light-emitting devices;

[0015] Place the sample in each of at least four light source areas;

[0016] Sunlight is irradiated into the first light source region, white fluorescence is irradiated into the second light source region, UV-cutoff light is irradiated into the third light source region, and the fourth light source region is kept unlit without receiving separate light from it; and

[0017] The photostability of the samples was evaluated by retrieving samples placed in at least four light source areas.

[0018] Beneficial effects

[0019] According to one embodiment of this application, a method can be provided for evaluating the photostability of materials used in the organic material layer of an organic light-emitting device, taking into account actual exposure environments. Specifically, the apparatus and method for evaluating photostability according to one embodiment of this application can quantitatively determine the occurrence and extent of denaturation caused by exposure of the corresponding material in the organic material layer of the organic light-emitting device.

[0020] Therefore, by using the apparatus and method for evaluating light stability according to one embodiment of this application, the changes in the organic material layer of an organic light-emitting device over time can be verified in advance. Thus, the apparatus and method can become a reliability evaluation standard in related industries. Attached Figure Description

[0021] Figure 1A diagram illustrating an apparatus for evaluating the photostability of an organic material layer for an organic light-emitting device, as described in one embodiment of this application.

[0022] Figure 2 A diagram illustrating the wavelength regions of a daylight source, a white fluorescent source, and a UV cutoff source according to one embodiment of this application.

[0023] Figure 3 A graph illustrating the degree of color change of the sample before and after exposure to sunlight in Embodiment 1 of this application.

[0024] Figures 4 to 8 The graphs show the results of HPLC measurements using the methods described in this application for evaluating photostability.

[0025] Figure 9 and Figure 10 The graphs show the results of colorimetric measurements using the methods for evaluating photostability described in this application.

[0026] [Figure Labels]

[0027] 10: First Light Source Area

[0028] 20: Second light source area

[0029] 30: Third Light Source Area

[0030] 40: Fourth Light Source Area Detailed Implementation

[0031] This application will be described in more detail below.

[0032] In this disclosure, the description of a component being placed "on" another component includes not only cases where one component is in contact with another component, but also cases where there is another component between the two components.

[0033] In this disclosure, unless otherwise stated to the contrary, the description that a part “includes” certain constituent elements means that it may also include other constituent elements, and does not exclude other constituent elements.

[0034] As described above, various materials have been developed that can be used as organic material layers in organic light-emitting devices (OLEDs). Furthermore, materials used in the organic material layers of OLEDs are susceptible to degradation when exposed to light and under various environmental conditions; however, there are no standardized standards, methods, etc., in the art for evaluating the photostability of materials used in the organic material layers of OLEDs. Therefore, this application aims to provide a method and apparatus for evaluating the photostability of materials used in the organic material layers of OLEDs, taking into account actual exposure environments.

[0035] An apparatus for evaluating the photostability of an organic material layer for an organic light-emitting device, according to one embodiment of this application, includes a photostability chamber having at least four light source regions, wherein the at least four light source regions include: a first light source region having a sunlight source; a second light source region having a white fluorescent source; a third light source region having a UV cutoff source; and a fourth light source region to which no light is irradiated.

[0036] In one embodiment of this application, at least four light source areas include: a first light source area provided with a daylight source; a second light source area provided with a white fluorescent source; a third light source area provided with a UV cutoff source; and a fourth light source area to which no light is irradiated.

[0037] The sunlight source in the first light source area is a substitute for natural light, and the environment in which it can be exposed in the material synthesis equipment of the organic material layer of the organic light-emitting device is considered. The color temperature of sunlight is approximately 4,000K.

[0038] The white fluorescent light source in the second light source area is considered to be exposed to an environment that can be used in the material synthesis equipment of the organic material layer of the organic light-emitting device and the material weighing chamber of the panel manufacturer. In this application, the white fluorescent light source may also be referred to as a cold daylight source, and the color temperature is about 6,500K.

[0039] The UV cutoff light source in the third light source area is a light source that removes UV wavelengths, and is designed for environments that can be exposed to, such as material purification equipment for the organic material layer of organic light-emitting devices and the manufacturing cleanroom of panel manufacturers. The color temperature of the UV cutoff light source is approximately 3,000K.

[0040] The fourth light source area is used for comparison with the first through third light source areas, and no light is shone into the fourth light source area. The fourth light source area may not be equipped with a daylight source, a white fluorescent source, or a UV cutoff source; instead, it may be equipped with a lamp, in which the lamp is turned off.

[0041] Furthermore, during the manufacturing process of the organic material layer of the organic light-emitting device and the panel manufacturing process of the organic light-emitting device, the organic material layer of the organic light-emitting device does not have the opportunity to be directly exposed to a UV light source. Therefore, in one embodiment of this application, a UV light source can be excluded.

[0042] Figure 2 The wavelength regions of a daylight source, a white fluorescent source, and a UV cutoff source according to one embodiment of this application are shown.

[0043] In one embodiment of this application, at least four light source areas can be independently maintained at a temperature of 15°C to 50°C and a humidity of 20% to 90%. Furthermore, at least four light source areas can be maintained at a temperature of 25°C and a humidity of 40% (typical temperature and humidity conditions in a material manufacturing environment). Additionally, at least four light source areas can each be maintained at a constant temperature and humidity, and all can be maintained at the same temperature and humidity. In this document, the temperature deviation can be ±1°C, and the humidity deviation can be ±2%.

[0044] In one embodiment of this application, at least four light source zones may each include a shelf on which a sample is placed. In this document, at least four light source zones are arranged vertically in a continuous sequence within a photostability chamber, and at least four light source zones may be separated from each other by shelves.

[0045] Figure 1 The image shows an apparatus for evaluating the photostability of an organic material layer for an organic light-emitting device, according to one embodiment of this application. Figure 1 As shown, an apparatus for evaluating the photostability of an organic material layer for an organic light-emitting device according to one embodiment of this application includes a photostability chamber comprising at least four light source regions, and the at least four light source regions include: a first light source region 10 provided with a sunlight source; a second light source region 20 provided with a white fluorescent source; a third light source region 30 provided with a UV cutoff source; and a fourth light source region 40 to which no light is irradiated.

[0046] Furthermore, according to another embodiment of this application, a method for evaluating the photostability of an organic material layer for an organic light-emitting device includes: preparing an apparatus for evaluating the photostability of an organic material layer for an organic light-emitting device; placing a sample in each of at least four light source regions; irradiating a first light source region with sunlight, irradiating a second light source region with white fluorescence, irradiating a third light source region with UV cutoff light, and keeping a fourth light source region without irradiating it with separate light; and evaluating the photostability of the sample by retrieving the sample placed in the at least four light source regions.

[0047] In a method for evaluating light stability according to one embodiment of this application, the description of at least four light source regions is the same as that provided above.

[0048] In one embodiment of this application, the irradiation time for sunlight, white fluorescence, and UV cutoff light can be from 0.5 hours to 12 hours and from 0.5 hours to 4 hours, respectively.

[0049] In one embodiment of this application, the evaluation of the photostability of a sample can be used to analyze the sample's colorimetry as well as its purity and impurities. In this document, regarding the colorimetry of the sample, a CIE L spectrophotometer can be used to measure it. * a * b * Color space. Furthermore, HPLC (High Performance Liquid Chromatography) can be used to analyze the purity and impurities of a sample.

[0050] HPLC, an analytical method for analyzing the purity and impurities of samples, involves separating materials dissolved in a solvent (mobile phase) through a column (stationary phase) and detecting them using a suitable detector. In HPLC analysis, the interaction between the analyte dissolved in the solvent and the stationary phase is a crucial factor. In the HPLC analysis of materials used in the organic material layers of organic light-emitting devices, a non-polar stationary phase and a polar mobile phase (solvent) are typically used. In this case, the polar material is eluted first, and molecules with lower polarity are eluted after a longer residence time in the stationary phase. Utilizing this principle, as the sample is passed through an HPLC column, the organic material layer material and other impurities in the sample can be separated and detected.

[0051] Using the method described above, photostability can be assessed by comparing the purity and impurities of samples exposed to light from four light source regions. Furthermore, the occurrence of photostability can be determined by detecting the generation of additional impurities compared to samples from the four light source regions. More specifically, the degree of photostability is proportional to the increase in the number and content of impurities, and for the corresponding light source, photostability can be assessed as low.

[0052] Regarding the colorimetry of the sample, a spectrophotometer can be used to analyze CIE L. * a * b * Value. L * The value represents brightness and can be divided into stages from 0 (black) to 100 (white), as well as values ​​with larger L values. * The value indicates a color close to white. * The value represents the relationship between red and green, with a positive (+) value indicating red and a negative (-) value indicating green. * The value represents yellow and blue, with a positive (+) value indicating yellow and a negative (-) value indicating blue. Such an L... * a * b * The value can be obtained by analyzing the reflectance or transmittance of the sample. In the analysis of materials used in the organic material layer of organic light-emitting devices, the sample is opaque, and this value can be obtained by analyzing the reflectance.

[0053] Using the method described above, the L of a sample exposed to light from four light source regions can be measured. * a * b * The photostability was assessed by comparing the values. Furthermore, the occurrence of photostability could be determined by comparing L values ​​with samples from four different light source regions. * a * b * The degree of variability is determined by the difference in values. * a * b * The difference in values ​​increases proportionally, and the photostability of the corresponding light source can be assessed as low.

[0054] According to one embodiment of this application, a method can be provided for evaluating the photostability of materials used in the organic material layer of an organic light-emitting device, taking into account actual exposure environments. Specifically, the apparatus and method for evaluating photostability according to one embodiment of this application can quantitatively determine the occurrence and extent of denaturation caused by exposure of the corresponding material in the organic material layer of the organic light-emitting device.

[0055] Therefore, by using the apparatus and method for evaluating light stability according to one embodiment of this application, the changes in the organic material layer of an organic light-emitting device over time can be verified in advance. Thus, the apparatus and method can become a reliability evaluation standard in related industries.

[0056] Invention Embodiments

[0057] In the following description, this application will be described in detail with reference to embodiments to specifically illustrate this application. However, embodiments of this application can be modified in various different forms, and the scope of this application should not be construed as limited to the embodiments described below. Embodiments of this application are provided to more fully describe this application to those skilled in the art.

[0058] <Example>

[0059] <Example 1>

[0060] Approximately 1.5 g of the organic material layer of the organic light-emitting device (an anthracene-based light-emitting layer material) was thinly dispersed and placed in a transparent petri dish. The petri dish was then covered with a glass dome to prepare the sample.

[0061] Preparation Figure 1The light-stabilizing chamber (VP500L from Votsch Industrietechnik GmbH) includes a first light source area 10 equipped with a daylight source; a second light source area 20 equipped with a white fluorescent source; a third light source area 30 equipped with a UV cutoff source; and a fourth light source area 40 that is not illuminated by the lamps when they are turned off. In this paper, the specific types of the daylight source, white fluorescent source, and UV cutoff source are as follows.

[0062] Daylight source: OSRAM L 18W / 640

[0063] White fluorescent light source: Philips TLD 18W / 865

[0064] UV cutoff light source: Philips TLD 18W / 830

[0065] For each of the first to fourth light source areas, at least four samples were introduced. The temperature and humidity conditions of the first to fourth light source areas in the photostability chamber were all set to be the same (25°C and 40%), and the irradiation time for each light was set to 0.5 hours, 1 hour, 2 hours and 4 hours. For each time, the samples were removed from the photostability chamber and analyzed.

[0066] Figure 3 The diagram shows the degree of color change of the sample before and after exposure to sunlight in Example 1.

[0067] <Experimental Example 1> HPLC Analysis

[0068] Figures 4 to 8 The results of HPLC measurements using the method for evaluating photostability described in this application are shown. Figures 4 to 8 The results show that exposure-induced impurities were generated under both sunlight and white fluorescence, and the impurities increased proportionally with the exposure time. Furthermore, in the same manner as under UV-cutoff light, no photodegradable impurities were detected.

[0069] <Experimental Example 2> Colorimetric Analysis

[0070] Figure 9 and Figure 10 The results of colorimetry measurements using the method for evaluating photostability described in this application are shown. Figure 9 and Figure 10 The results show that, similar to those obtained by HPLC measurements, the color change progression is proportional to time under both sunlight and white fluorescence. Furthermore, as... Figure 10 The results show that L was determined under sunlight and white fluorescence. * value and b *The value changes due to color variations caused by exposure.

[0071] Therefore, the results of Experiments 1 and 2 indicate that the photostability is low under sunlight and white fluorescence conditions, and that photostability is maintained under UV cutoff light conditions, since discoloration and impurities were determined after 0.5 hours.

[0072] As shown in the above results, according to one embodiment of this application, a method can be provided for evaluating the photostability of materials used in the organic material layer of an organic light-emitting device, taking into account actual exposure environments. Specifically, through the apparatus and method for evaluating photostability according to one embodiment of this application, the occurrence and degree of denaturation caused by exposure of the corresponding material in the organic material layer of the organic light-emitting device can be quantitatively determined.

[0073] Therefore, by using the apparatus and method for evaluating light stability according to one embodiment of this application, the changes in the organic material layer of an organic light-emitting device over time can be verified in advance. Thus, the apparatus and method can become a reliability evaluation standard in related industries.

Claims

1. A method for evaluating the photostability of an organic material layer in an organic light-emitting device, the method comprising: An apparatus is prepared for evaluating the photostability of materials used in organic material layers of organic light-emitting devices, the apparatus comprising a photostability chamber having at least four light source regions: The first light source area is set up with a daylight source with a color temperature of approximately 4,000 K; A second light source area is provided, which has a white fluorescent light source with a color temperature of approximately 6,500 K; A third light source region is provided, comprising a UV-cutoff light source with a color temperature of approximately 3,000 K and whose light is confined to the wavelength region between approximately 500 nm and 700 nm; and The fourth light source region that does not receive light from it. A sample of the material is placed in each of the at least four light source regions; The first light source region is irradiated with sunlight of a color temperature of about 4,000 K, the second light source region is irradiated with white fluorescence of a color temperature of about 6,500 K, the third light source region is irradiated with UV cutoff light of a color temperature of about 3,000 K and whose wavelength range is only between about 500 nm and 700 nm, and the fourth light source region is kept irradiated without irradiating the fourth light source region with separate light. as well as The photostability of the samples is evaluated by retrieving each of the samples placed in the at least four light source areas and comparing each sample illuminated in the first, second, and third light source areas with an unilluminated sample in the fourth light source area, wherein the illumination time of the sunlight, the white fluorescence, and the UV cutoff light is from 0.5 hours to 12 hours.

2. The method for evaluating the photostability of an organic material layer for an organic light-emitting device according to claim 1, wherein the at least four light source regions are each independently maintained at a temperature of 15°C to 50°C and a humidity of 20% to 90%.

3. The method for evaluating the photostability of an organic material layer for an organic light-emitting device according to claim 2, wherein all at least four light source regions are maintained at the same temperature and humidity.

4. The method for evaluating the photostability of an organic material layer for an organic light-emitting device according to claim 1, wherein each of the at least four light source regions further includes a shelf on which a sample is placed.

5. The method for evaluating the photostability of an organic material layer for an organic light-emitting device according to claim 4, wherein the at least four light source regions are arranged vertically in a continuous sequence in the photostability chamber; and The at least four light source areas are separated from each other by the shelf.

6. The method for evaluating the photostability of an organic material layer for an organic light-emitting device according to claim 1, wherein the evaluation of the photostability of the sample is performed by analyzing the chromaticity of the sample and the purity and impurities of the sample.

7. The method for evaluating the photostability of organic material layers for organic light-emitting devices according to claim 6, wherein the chromaticity of the sample is measured using a spectrophotometer using CIE L. * a * b * Color space.

8. The method for evaluating the photostability of an organic material layer for an organic light-emitting device according to claim 6, wherein the purity and impurities of the sample are analyzed using high-performance liquid chromatography.

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