Material screening method and light emitting device

Abstract

This application discloses a material screening method and a light-emitting device. The first aspect of the material screening method involves screening the light-emitting layer material for a light-emitting device, configuring multiple groups of light-emitting materials, providing multiple groups of monochromatic light-emitting devices, using each group of light-emitting materials as the light-emitting layer material, and obtaining the electroluminescence characterization lifetime parameter T1 of the first monochromatic light-emitting device in each group of monochromatic light-emitting devices. i Simultaneously, the photoluminescence characterization lifetime parameter T2 of the second monochromatic light-emitting device in each group of monochromatic light-emitting devices was obtained. i According to the electroluminescence characterization lifetime parameter T1 corresponding to each group of monochromatic light-emitting devices i Photoluminescence characterization lifetime parameter T2 i The target luminescent material group is selected from multiple groups of luminescent materials to serve as the luminescent layer material for the luminescent device. This improves the overall luminescent lifespan of the luminescent device, thereby extending the long-term lifespan of the display panel and preventing color shift issues during long-term use.

Description

Technical Field

[0001] This invention relates to the field of display, and more specifically to a material screening method and a light-emitting device. Background Technology

[0002] Organic light-emitting diode (OLED) display panels are widely used in various consumer electronics products such as mobile phones, televisions, personal digital assistants, digital cameras, laptops, and desktop computers due to their advantages such as high image quality, energy saving, thin body and wide range of applications, making them the mainstream display panels in the display field.

[0003] However, typical OLED display panels include various light-emitting devices with different colors of light emission. The light-emitting devices with different colors of light emission decay at different rates during long-term use of the display panel. As a result, after long-term use, some light-emitting devices decay too quickly and fail to emit light, leading to color deviation in the display panel and affecting the display effect. Therefore, there is an urgent need for a material screening method and a new type of light-emitting device. Summary of the Invention

[0004] This application provides a material screening method and a light-emitting device. The light-emitting layer material of the light-emitting device selected using the material screening method of the first aspect of this application can improve the overall luminous lifespan of the light-emitting device, thereby extending the long-term lifespan of the display panel, avoiding color shift problems during long-term use, improving the display effect of the display panel under long-term use, and enhancing the user experience.

[0005] The first aspect of this application provides a material screening method for screening the light-emitting layer material of a light-emitting device. The screening method includes:

[0006] Multiple groups of luminescent materials are configured, each group consisting of a host material and a guest material.

[0007] Multiple sets of monochromatic light-emitting devices are provided. Each set of light-emitting materials is used as the light-emitting layer material to fabricate multiple sets of monochromatic light-emitting devices with light-emitting layers. Each set of monochromatic light-emitting devices includes the same first monochromatic light-emitting device and second monochromatic light-emitting device.

[0008] Obtain the electroluminescence characterization lifetime parameter T1 of the first monochromatic light-emitting device in each group of monochromatic light-emitting devices. i Simultaneously, the photoluminescence characterization lifetime parameter T2 of the second monochromatic light-emitting device in each group of monochromatic light-emitting devices was obtained. i ;

[0009] Based on the electroluminescence characterization lifetime parameter T1 corresponding to each group of monochromatic light-emitting devices i Photoluminescence characterization lifetime parameter T2i The target luminescent material group is selected from multiple groups of luminescent materials to serve as the luminescent layer material for luminescent devices.

[0010] In one possible implementation of the first aspect of this application, the electroluminescence characterization lifetime parameter T1 corresponding to each group of monochromatic light-emitting devices is used. i Photoluminescence characterization lifetime parameter T2 i The step of selecting a target luminescent material group from multiple groups of luminescent materials to serve as the luminescent layer material for a luminescent device includes:

[0011] The electroluminescence characterization lifetime parameter T1 corresponding to each group of monochromatic light-emitting devices is... i and the photoluminescence characterization lifetime parameter T2 i By comparison, those that meet the lifetime parameter T2 for photoluminescence characterization are selected. i Less than the electroluminescence characterization lifetime parameter T1 i The light-emitting materials corresponding to each group of monochromatic light-emitting devices are used to form the first group of light-emitting materials.

[0012] Preferably, the lifetime parameter T1 is characterized using standard electroluminescence. a One or more target luminescent material groups are obtained by screening from the first group of luminescent materials.

[0013] In one possible implementation of the first aspect of this application, the light-emitting layer material is a blue light-emitting layer material.

[0014] Standard electroluminescence characterization lifetime parameter T1 a The value range is 0% to 2%, where the standard electroluminescence characterization lifetime parameter T1 a The degree of brightness decay of a monochromatic light-emitting device within a first preset emission time; preferably, the standard electroluminescence characterization lifetime parameter T1. a The value range is 1% to 2%; preferably, the first preset luminescence time is 200 hours; or,

[0015] The light-emitting layer material is either red or green.

[0016] Standard electroluminescence characterization lifetime parameter T1 a The value range is 0% to 1%, where the standard electroluminescence characterization lifetime parameter T1 a The degree of brightness decay of a monochromatic light-emitting device within a first preset light-emitting time;

[0017] Preferably, the first preset luminescence time is 200 hours.

[0018] In one possible implementation of the first aspect of this application, in the step of configuring multiple groups of luminescent materials:

[0019] Each group of luminescent materials contains the same host material, but the guest materials in each group are different from each other.

[0020] In one possible implementation of the first aspect of this application, the electroluminescence characterization lifetime parameter T1 of the first monochromatic light-emitting device in each group of monochromatic light-emitting devices is obtained. i Simultaneously, the photoluminescence characterization lifetime parameter T2 of the second monochromatic light-emitting device in each group of monochromatic light-emitting devices was obtained. i The steps include:

[0021] Photoluminescence testing was performed on the second monochromatic light-emitting device in each group of monochromatic light-emitting devices to obtain the photoluminescence characterization lifetime parameter T2 of the second monochromatic light-emitting device. i ;

[0022] In the photoluminescence test, a second monochromatic light-emitting device is optically excited using an excitation source with a first preset wavelength. The first luminescence intensity I of the second monochromatic light-emitting device under the optical excitation of the first excitation source is detected and recorded, and the first luminescence time t of the second monochromatic light-emitting device is also recorded. Based on the first luminescence intensity I and the first luminescence time t, the photoluminescence characterization lifetime parameter T2 corresponding to the second monochromatic light-emitting device is obtained. i .

[0023] In one possible implementation of the first aspect of this application, obtaining the first preset wavelength includes the following steps:

[0024] Provide a test monochromatic light-emitting device. The test monochromatic light-emitting device and the second monochromatic light-emitting device in each group of monochromatic light-emitting devices have the same device structure and light-emitting color of the light-emitting layer.

[0025] In testing monochromatic light-emitting devices, at least two light-emitting units with different brightness attenuation levels are selected. Among them, the light-emitting unit with an attenuation level of 0% is used as the reference light-emitting unit, and the light-emitting unit with an attenuation level greater than 0% is used as the comparison light-emitting unit.

[0026] In the thickness direction of the tested monochromatic light-emitting device, a first cross-section is taken in the device region corresponding to the reference light-emitting unit, and at least the light-emitting layer, electron transport layer and hole transport layer in the reference light-emitting unit are exposed through the first cross-section;

[0027] Photoluminescence absorption spectroscopy was performed on the first cross-section of the reference light-emitting unit to obtain the optimal absorption wavelengths of the light-emitting layer, electron transport layer, and hole transport layer in the photoluminescence spectrum.

[0028] In one possible implementation of the first aspect of this application, the step of obtaining the first preset wavelength further includes:

[0029] In the thickness direction of the tested monochromatic light-emitting device, a second cross-section is taken for the device region corresponding to each comparison light-emitting unit, and at least the light-emitting layer, electron transport layer and hole transport layer in each comparison light-emitting unit are exposed through the second cross-section;

[0030] Photoluminescence tests were performed on the first and second cross-sections along the thickness direction of the tested monochromatic light-emitting device using excitation light sources with optimal absorption wavelengths, respectively, to obtain the photoluminescence intensity of the reference light-emitting unit and each comparison light-emitting unit.

[0031] The first preset wavelength is obtained based on the photoluminescence intensity of the reference light-emitting unit corresponding to each excitation light source with the optimal absorption wavelength and the comparison light-emitting unit.

[0032] In one possible implementation of the first aspect of this application, the step of obtaining a first preset wavelength based on the photoluminescence intensity of a reference light-emitting unit corresponding to an excitation light source having an optimal absorption wavelength and a comparison light-emitting unit includes:

[0033] The photoluminescence intensity of the reference light-emitting unit and the comparison light-emitting unit corresponding to each excitation light source with the optimal absorption wavelength are compared, and the optimal absorption wavelength corresponding to the maximum difference between the photoluminescence intensity of the reference light-emitting unit and the comparison light-emitting unit is selected as the first preset wavelength.

[0034] Preferably, the first preset wavelength is the optimal absorption wavelength of the light-emitting layer in the photoluminescence spectrum.

[0035] In one possible implementation of the first aspect of the embodiments of this application,

[0036] The electroluminescence characterization lifetime parameter T1 of the first monochromatic light-emitting device in each group of monochromatic light-emitting devices is obtained. i Simultaneously, the photoluminescence characterization lifetime parameter T2 of the second monochromatic light-emitting device in each group of monochromatic light-emitting devices was obtained. i The steps include:

[0037] Under the same constant current conditions, the first monochromatic light-emitting device in each group of monochromatic light-emitting devices is controlled to emit electroluminescence. The second luminescence intensity I' of each first monochromatic light-emitting device under the same constant current conditions is detected and recorded. At the same time, the second luminescence time t' of the first monochromatic light-emitting device is also recorded. Based on the second luminescence intensity I' and the second luminescence time t', the electroluminescence characterization lifetime parameter T1 corresponding to each first monochromatic light-emitting device is obtained. i .

[0038] A second aspect of this application provides a light-emitting device, comprising:

[0039] The light-emitting layer has a light-emitting host material and a light-emitting object material;

[0040] Photoluminescence characterization lifetime parameter T2 of luminescent object material i Less than the electroluminescence characterization lifetime parameter T1 i ,

[0041] And the lifetime parameter T1 of electroluminescence characterization i Less than the standard electroluminescence characterization lifetime parameter T1 a Standard electroluminescence characterization lifetime parameter T1 a The value range is 0% to 2%, where the standard electroluminescence characterization lifetime parameter T1 a The degree of brightness decay of the light-emitting device within the first preset light-emitting time;

[0042] Preferably, the standard electroluminescence characterization lifetime parameter T1 a The value range is 1% to 2%;

[0043] Preferably, the first preset luminescence time is 200 hours.

[0044] The second aspect of this application improves the luminous lifespan of the light-emitting device, thereby improving the overall luminous lifespan of the display panel and optimizing the display effect and display quality of the display panel. Attached Figure Description

[0045] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings, in which the same or similar reference numerals denote the same or similar features, and the drawings are not drawn to scale.

[0046] Figure 1 This is a flowchart of one step in the material screening method of the first aspect of the present application;

[0047] Figure 2 This is an example diagram of the layer structure of the first light-emitting unit in the first aspect of the embodiments of this application;

[0048] Figure 3 This is an experimental result diagram of photoluminescence testing of the cross-section of multiple light-emitting units using an excitation light source with a wavelength of 460 nm, as described in the first aspect of the embodiments of this application.

[0049] Figure 4 This is an experimental result diagram of photoluminescence testing of the cross-section of multiple light-emitting units using an excitation light source with a wavelength of 410 nm, as described in the first aspect of the embodiments of this application.

[0050] Figure 5 This is an experimental result diagram of photoluminescence testing of the cross-section of multiple light-emitting units using an excitation light source with a wavelength of 390 nm, as described in the first aspect of the embodiments of this application.

[0051] Figure 6 This is another step flowchart in the material screening method of the first aspect of the embodiments of this application;

[0052] Figure 7 This is a flowchart of another step in the material screening method of the first aspect of the present application;

[0053] Figure 8 This is a flowchart of another step in the material screening method of the first aspect of the present application;

[0054] Figure 9 The results are the photoluminescence test results or electroluminescence test results of each light-emitting device in a set of experiments in the first aspect of the embodiments of this application.

[0055] Cathode layer-1, electron transport layer-2; light-emitting layer-3; hole transport layer-4; hole injection layer-5; anode layer-6;

[0056] First facet - X. Detailed Implementation

[0057] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the invention.

[0058] The inventors discovered in their research that the light-emitting devices of different colors in OLED display panels experience varying degrees of lifespan decay. Therefore, during long-term use, light-emitting devices with shorter lifespans may fail to emit light or only emit low-brightness light, leading to overall color shift in the display and affecting the display effect.

[0059] In some examples, OLED display panels have three light-emitting devices that emit red, green, and blue light. The inventors discovered that the lifespan of blue light-emitting devices is generally shorter than that of green and red light-emitting devices. This means that the brightness of blue light-emitting devices decays faster over long-term use, causing the display panel to gradually shift towards red or green hues, significantly reducing display quality and color accuracy. Therefore, it is necessary to improve the lifespan of blue light-emitting devices to match that of green and red light-emitting devices, thereby improving the overall display lifespan and long-term display performance.

[0060] The inventors discovered through in-depth research that photoluminescence and electroluminescence tests can be performed on light-emitting devices, and the results can be used to screen for light-emitting layer materials that improve the lifespan of the devices. However, the layer structure of light-emitting devices in OLED display panels is complex, with multiple stacked functional layers. Generally, the functional layers of a display panel include hole injection layers, hole transport layers, light-emitting layers, electron transport layers, and electron injection layers. While electroluminescence is used in light-emitting devices, determining the emission wavelength of the excitation light source during electroluminescence testing, and ensuring that the change in luminous intensity over time when the device is irradiated with that wavelength, is a challenging task as a parameter for the photoluminescence lifetime of the device.

[0061] Photoluminescence (PL) generally refers to the process by which electrons transition from the valence band to the conduction band in a material under the excitation of light, leaving holes in the valence band. The electrons and holes relax in their respective conduction and valence bands to reach their lowest unoccupied excited states (the bottom of the conduction band and the top of the valence band in intrinsic semiconductors), becoming quasi-equilibrium states. The electrons and holes in these quasi-equilibrium states then recombine to emit light. Different materials emit light with different characteristic wavelengths and intensities under light excitation. Photoluminescence processes include fluorescence and phosphorescence.

[0062] In view of this, the first aspect of this application provides a material screening method, please refer to [link to relevant documentation]. Figure 1 Obtaining the first preset wavelength includes the following steps:

[0063] S01: Provides a test monochromatic light-emitting device, which includes a light-emitting layer that emits monochromatic light.

[0064] In some examples, the test monochromatic light-emitting device includes a light-emitting layer, an electron transport layer, and a hole transport layer. The light-emitting material of the light-emitting layer includes a host material and a guest material. The test monochromatic light-emitting device has the same device structure and light-emitting color as the second monochromatic light-emitting device in each group of monochromatic light-emitting devices in step S02 below.

[0065] In some examples, the host material can be a carbazole group derivative, an arylsilane derivative, an aromatic derivative, a metal complex derivative, etc. The guest material can be a fluorescent dopant (e.g., porphyrin compounds, coumarin dyes, quinacridone compounds, aromatic amine compounds, etc.) or a phosphorescent dopant (e.g., a complex containing iridium metal, etc.).

[0066] S02: Select at least two light-emitting units with different brightness attenuation levels in the test of the monochromatic light-emitting device. Among them, the light-emitting unit with an attenuation level of 0% is used as the reference light-emitting unit, and the light-emitting unit with an attenuation level greater than 0% is used as the comparison light-emitting unit.

[0067] In some embodiments, the test monochromatic light-emitting device includes multiple light-emitting units capable of independent emission. It can be controlled that, at the same current density, the initial luminous intensity of the reference light-emitting unit and the comparison light-emitting unit are the same, but their attenuation levels (attenuation level being the degree of brightness decay of the light-emitting unit) differ. The reference light-emitting unit, serving as a comparative example, should have its attenuation level controlled to 0%.

[0068] S03: In the thickness direction of the tested monochromatic light-emitting device, a first cross-section is taken in the device region corresponding to the reference light-emitting unit, and at least the light-emitting layer, electron transport layer and hole transport layer in the reference light-emitting unit are exposed through the first cross-section;

[0069] Photoluminescence absorption spectroscopy was performed on the first cross-section of the reference light-emitting unit to obtain the optimal absorption wavelengths of the light-emitting layer, electron transport layer, and hole transport layer in the photoluminescence spectrum.

[0070] In some examples, during photoluminescence absorption spectroscopy testing of the first cross-section of a reference light-emitting unit, an excitation light source with continuously varying wavelengths is used to irradiate and excite the light-emitting layer, electron transport layer, and hole transport layer to perform photoluminescence testing; and the luminescence intensity of the light-emitting layer, electron transport layer, and hole transport layer under excitation light sources of different wavelengths is collected. The wavelength of the excitation light source corresponding to the strongest luminescence intensity in the functional layers (e.g., light-emitting layer, electron transport layer, and hole transport layer) of the light-emitting device is the optimal absorption wavelength of that functional layer in the photoluminescence absorption spectrum.

[0071] S04: In the thickness direction of the tested monochromatic light-emitting device, a second cross-section is taken for the device region corresponding to each comparative light-emitting unit, and at least the light-emitting layer, electron transport layer and hole transport layer in each comparative light-emitting unit are exposed through the second cross-section.

[0072] Using excitation light sources with optimal absorption wavelengths, i.e., excitation light sources with the optimal absorption wavelengths obtained in step S03, photoluminescence tests are performed along the thickness direction of the test monochromatic light-emitting device on the first and second cross-sections respectively, and the photoluminescence intensity of the reference light-emitting unit and each comparison light-emitting unit is obtained respectively.

[0073] S05: Obtain the first preset wavelength based on the reference light-emitting unit corresponding to each excitation light source with the optimal absorption wavelength and the photoluminescence intensity of each comparison light-emitting unit.

[0074] In some optional embodiments, step S05 further includes:

[0075] S051, compare the photoluminescence intensity of the reference light-emitting unit and the comparison light-emitting unit corresponding to each excitation light source with the optimal absorption wavelength, and select the optimal absorption wavelength corresponding to the maximum difference between the photoluminescence intensity of the reference light-emitting unit and the comparison light-emitting unit as the first preset wavelength.

[0076] In some embodiments, the first preset wavelength is the optimal absorption wavelength of the light-emitting layer in the photoluminescence spectrum.

[0077] The following example illustrates the steps for obtaining the first preset wavelength.

[0078] S01': Fabricate a test monochromatic light-emitting device, which includes multiple independently controllable light-emitting units. The test monochromatic light-emitting device includes an anode, a hole injection layer, a hole transport layer, a light-emitting layer having host and guest materials, an electron transport layer, and a cathode layer stacked sequentially.

[0079] S02': In this example, the tested monochromatic light-emitting device is a blue light-emitting device. Four light-emitting units are selected from this blue light-emitting device for testing. These four light-emitting units are the first light-emitting unit, the second light-emitting unit, the third light-emitting unit, and the fourth light-emitting unit. The four light-emitting units are controlled at the same current density (e.g., 50 mA / cm²). 2 The system emits light, controlling the initial brightness of the four light-emitting units to be the same, but with different degrees of brightness decay. Taking the first light-emitting unit as a comparison, the brightness decay of the first light-emitting unit is controlled to be 0%, meaning the brightness of the first light-emitting unit is 100%; the brightness decay of the second light-emitting unit is controlled to be 10%, meaning the brightness of the second light-emitting unit decays to 90%; the brightness decay of the third light-emitting unit is controlled to be 50%, meaning the brightness of the third light-emitting unit decays to 50%; and the brightness decay of the fourth light-emitting unit is controlled to be 75%, meaning the brightness of the fourth light-emitting unit decays to 25%.

[0080] S03': Take a first cross-section in the thickness direction of the test monochromatic light-emitting device, corresponding to the device region of the first light-emitting unit. In this example, please refer to... Figure 2Before taking the first cross-section X of the first light-emitting unit, a portion of the cathode layer 1 corresponding to the first light-emitting unit is peeled off. The remaining functional layers are then subjected to the first cross-section, exposing the anode layer 6, hole injection layer 5, hole transport layer 4, light-emitting layer 3, and electron transport layer 2 through the first cross-section X. In this example, the first cross-section X is an oblique cut that forms an acute angle with the light-emitting direction of the light-emitting device. In other examples, the first cross-section may also be a straight cut parallel to the light-emitting direction of the light-emitting device. In this example, the length of the first cross-section X in the thickness direction of the tested monochromatic light-emitting device is 400 μm. The starting point of the length coordinate of the first cross-section is the side of the electron transport layer facing away from the light-emitting layer, which is 0 μm; the ending point of the length coordinate of the first cross-section is the side of the anode facing away from the light-emitting layer, which is 400 μm. The electron transport layer is located at approximately 130 μm, the light-emitting layer at approximately 260 μm, and the hole transport layer at approximately 390 μm. Photoluminescence absorption spectra of the electron transport layer, the luminescent layer, and the hole transport layer exposed through the first cross-section were measured. The optimal absorption wavelength of the luminescent layer in the photoluminescence spectrum was found to be 460 nm, the optimal absorption wavelength of the electron transport layer was 390 nm, and the optimal absorption wavelength of the hole transport layer was 410 nm.

[0081] S04': In the thickness direction of the tested monochromatic light-emitting device, a second cross-section is taken in the device region corresponding to the second light-emitting unit. The anode layer, hole injection layer, hole transport layer, light-emitting layer, and electron transport layer in the second light-emitting unit are exposed through the second cross-section. Similarly, in the thickness direction of the tested monochromatic light-emitting device, a third cross-section is taken in the device region corresponding to the third light-emitting unit. The anode layer, hole injection layer, hole transport layer, light-emitting layer, and electron transport layer in the third light-emitting unit are exposed through the third cross-section. In the thickness direction of the tested monochromatic light-emitting device, a fourth cross-section is taken in the device region corresponding to the fourth light-emitting unit. The anode layer, hole injection layer, hole transport layer, light-emitting layer, and electron transport layer in the fourth light-emitting unit are exposed through the fourth cross-section.

[0082] Please see Figure 3 Using a first excitation light source with a wavelength of 460nm, photoluminescence tests were performed on the first, second, third, and fourth cross-sections along the thickness direction of the tested monochromatic light-emitting device, and the photoluminescence intensity of the first, second, third, and fourth light-emitting units was obtained.

[0083] Please see Figure 4Using a second excitation light source with a wavelength of 410nm, photoluminescence tests were performed on the first, second, third, and fourth cross-sections along the thickness direction of the tested monochromatic light-emitting device, respectively, to obtain the photoluminescence intensity of the first, second, third, and fourth light-emitting units.

[0084] Please see Figure 5 A third excitation light source with a wavelength of 390nm was used to perform photoluminescence tests along the thickness direction of the test monochromatic light-emitting device on the first, second, third, and fourth cross-sections, respectively, and to obtain the photoluminescence intensity of the first, second, third, and fourth light-emitting units.

[0085] S05': Obtain the first preset wavelength based on the photoluminescence intensity of the first light-emitting unit, the second light-emitting unit, the third light-emitting unit, and the fourth light-emitting unit corresponding to each excitation light source with the optimal absorption wavelength.

[0086] S051': Compare the photoluminescence intensities of the first, second, third, and fourth light-emitting units corresponding to each excitation light source with the optimal absorption wavelength, and select the optimal absorption wavelength corresponding to the largest difference between the photoluminescence intensities of the first, second, third, and fourth light-emitting units as the first preset wavelength.

[0087] In some embodiments, the first preset wavelength is the optimal absorption wavelength of the light-emitting layer in the photoluminescence spectrum.

[0088] In this example, please see, Figures 3 to 5 As can be seen from the three figures above, when using the optimal absorption wavelengths of the electron transport layer (390 nm) and the hole transport layer (410 nm) as excitation sources to perform photoluminescence tests on light-emitting units with different brightness decay rates, the intensity of light emitted from the corresponding cross-sections of different light-emitting units is not significantly different. This indicates that when using the optimal absorption wavelengths of the electron transport layer (390 nm) and the hole transport layer (410 nm) as excitation sources to stimulate photoluminescence in light-emitting devices, the brightness decay rate of the light-emitting device cannot be reflected by the luminous intensity of the device.

[0089] When photoluminescence tests were conducted on light-emitting units with different brightness attenuation levels using 460nm as the optimal absorption wavelength of the light-emitting layer in the photoluminescence spectrum as the excitation light source, the intensity of light emitted from the cross-sections of different light-emitting units showed significant differences. Figure 3 compared to Figure 4 as well as Figure 5 When the first, second, third, and fourth light-emitting units were subjected to photoluminescence testing under the same wavelength excitation, the differences in photoluminescence intensity among them were the greatest. The first light-emitting unit exhibited the lowest brightness decay, thus resulting in the highest photoluminescence intensity on the first cross-section. As the brightness decay of the light-emitting units increased, the photoluminescence intensity on the corresponding cross-sections of those units gradually decreased; the fourth light-emitting unit exhibited the highest brightness decay, thus resulting in the highest photoluminescence intensity on the fourth cross-section.

[0090] In short Figure 3 Analysis was conducted using the optimal absorption wavelength of the emissive layer in the photoluminescence spectrum (460 nm) as the excitation light source to perform photoluminescence tests on light-emitting units with different degrees of brightness decay. The greater the brightness decay, the weaker the photoluminescence intensity of the light-emitting unit. This indicates that during long-term use, the decomposition and failure of the luminescent material in the emissive layer lead to a decrease in the emissive layer's own luminous efficiency. This decrease in the emissive layer's own luminous efficiency significantly impacts the lifespan of the light-emitting device, directly causing luminous decay and a shortened lifespan. Therefore, photoluminescence testing can be used to determine the degree of decay in the emissive layer's own luminous efficiency and its lifespan. Furthermore, using the optimal absorption wavelength of the emissive layer in the photoluminescence spectrum as the first preset wavelength for photoluminescence testing can reflect the lifespan of the emissive layer and the overall brightness decay of the light-emitting device.

[0091] Furthermore, the first aspect of this application provides a material screening method, please refer to [link to relevant documentation]. Figure 6 The screening method for the light-emitting layer material of light-emitting devices includes:

[0092] S10, configured with multiple groups of luminescent materials, each group of luminescent materials including a host material and a guest material.

[0093] In some optional embodiments, the host materials included in each group of luminescent materials in step S10 are all the same, while the guest materials included in each group of luminescent materials are different from each other.

[0094] S20 provides multiple sets of monochromatic light-emitting devices, using each set of light-emitting materials as the light-emitting layer material, and fabricates multiple sets of monochromatic light-emitting devices with light-emitting layers respectively. Each set of monochromatic light-emitting devices includes the same first monochromatic light-emitting device and second monochromatic light-emitting device.

[0095] S30, Obtain the electroluminescence characterization lifetime parameter T1 of the first monochromatic light-emitting device in each group of monochromatic light-emitting devices. i Simultaneously, the photoluminescence characterization lifetime parameter T2 of the second monochromatic light-emitting device in each group of monochromatic light-emitting devices was obtained.i .

[0096] S40, based on the electroluminescence characterization lifetime parameter T1 corresponding to each group of monochromatic light-emitting devices i Photoluminescence characterization lifetime parameter T2 i The target luminescent material group is selected from multiple groups of luminescent materials to serve as the luminescent layer material for luminescent devices.

[0097] In some embodiments, electroluminescence characterization lifetime parameters refer to parameters that can reflect and characterize the luminescence lifetime of a light-emitting device in electroluminescence testing. Photoluminescence characterization lifetime parameters refer to parameters that can reflect and characterize the luminescence lifetime of a light-emitting device in photoluminescence testing.

[0098] In some alternative embodiments, please refer to Figure 7 Step S30 includes:

[0099] S31, Perform photoluminescence testing on the second monochromatic light-emitting device in each group of monochromatic light-emitting devices to obtain the photoluminescence characterization lifetime parameter T2 of the second monochromatic light-emitting device. i ;

[0100] In the photoluminescence test, a second monochromatic light-emitting device is optically excited using an excitation source with a first preset wavelength. The first luminescence intensity I of the second monochromatic light-emitting device under the optical excitation of the first excitation source is detected and recorded, and the first luminescence time t of the second monochromatic light-emitting device is also recorded. Based on the first luminescence intensity I and the first luminescence time t, the photoluminescence characterization lifetime parameter T2 corresponding to the second monochromatic light-emitting device is obtained. i .

[0101] S32, Under the same constant current condition, control the first monochromatic light-emitting device in each group of monochromatic light-emitting devices to perform electroluminescence, detect and record the second luminescence intensity I' of each first monochromatic light-emitting device under the same constant current condition, and simultaneously record the second luminescence time t' of the first monochromatic light-emitting device, and obtain the electroluminescence characterization lifetime parameter T1 corresponding to each first monochromatic light-emitting device based on the second luminescence intensity I' and the second luminescence time t'. i .

[0102] In some alternative embodiments, please refer to Figure 8 Step S40 includes:

[0103] S41, the electroluminescence characterization lifetime parameter T1 corresponding to each group of monochromatic light-emitting devices i and the photoluminescence characterization lifetime parameter T2 i By comparison, those that meet the lifetime parameter T2 for photoluminescence characterization are selected. i Less than the electroluminescence characterization lifetime parameter T1 iThe light-emitting materials corresponding to each group of monochromatic light-emitting devices are used to form the first group of light-emitting materials.

[0104] In some optional embodiments, step S40 further includes:

[0105] S42, using standard electroluminescence to characterize lifetime parameter T1 a One or more target luminescent material groups are obtained by screening from the first group of luminescent materials.

[0106] The inventors further discovered that in OLED display panels, during long-term use, blue light-emitting devices generally have a shorter lifespan and faster brightness decay compared to red and green light-emitting devices. Therefore, after prolonged use, the display panel often exhibits a reddish or greenish tint during display. In some optional embodiments, the light-emitting layer material is a blue light-emitting guest material, and the standard electroluminescence characterization lifetime parameter T1... a The value range is 0% to 2%, where the standard electroluminescence characterization lifetime parameter T1 a This represents the degree of brightness decay of a monochromatic light-emitting device within a first preset emission time. In some embodiments, the standard electroluminescence characterization lifetime parameter T1... a The value range is 1% to 2%. Generally, blue light-emitting devices (LEDs) experience rapid lifespan decay. If the electroluminescence lifetime parameter value for a blue LED is greater than 2%, the rate of brightness decay increases, resulting in a lower actual brightness compared to the required brightness. Since the lifespans of red and green LEDs are longer than those of blue LEDs, the overall display panel may appear reddish or greenish, causing color shift. When the electroluminescence lifetime parameter value for a blue LED is within the range of 1% to 2%, it indicates good stability of the light-emitting layer material, excellent overall luminous performance, and an increased lifespan, thus improving the overall lifespan of the display panel and preventing color shift during long-term use. In some embodiments, the first preset luminous time is 200 hours. In these embodiments, the blue light-emitting material obtained through this material screening method can improve the lifespan of the blue LED, thereby increasing the overall lifespan of the display panel and solving the color shift problem. Since the luminescent object material is the main material for luminescence in both phosphorescent and fluorescent luminescent materials, the material screening method of this application can be used to screen the luminescent object material more accurately to select the material of the luminescent layer. This allows for more targeted screening of the luminescent object material in the luminescent layer to improve the overall luminescent life of the luminescent device and the accuracy of the color rendering of the display panel.

[0107] In some optional embodiments, the light-emitting layer material is a red light-emitting guest material or a green light-emitting guest material, and the standard electroluminescence characterization lifetime parameter T1 is used. a The value range is 0% to 1%, where the standard electroluminescence characterization lifetime parameter T1 a This refers to the degree of brightness decay of a monochromatic light-emitting device within a first preset emission time. During their research, the inventors discovered that the lifespan of red and green light-emitting devices in a display panel is longer than that of blue light-emitting devices. Therefore, it is necessary to raise the screening standards for the light-emitting layer materials of green and red light-emitting devices to effectively select light-emitting layer materials that improve the lifespan of red or green light-emitting devices. Generally, if the electroluminescence lifetime parameter value of red or green light-emitting devices is greater than 1%, the lifespan of red or green light-emitting devices is relatively short, and color shift problems may occur in the display panel during long-term use. In some embodiments, the first preset emission time is 200 hours. In these embodiments, using the material screening method of the first aspect of this application to screen the light-emitting layer materials of red and green light-emitting devices can improve the lifespan of red and green light-emitting devices, thereby improving the overall lifespan of the display panel, while avoiding color shift problems in the display panel during long-term use, further improving the display quality of the display panel.

[0108] To further demonstrate the improvement in the overall lifespan of the light-emitting device by the light-emitting layer material selected by the material screening method in the first aspect of the present application, a series of experiments were conducted, including Comparative Example 1 and Experimental Example 1. Experimental Example 1 is the light-emitting layer material selected by the material screening method in the first aspect of the present application, while Comparative Example 1 is an arbitrarily selected common light-emitting layer material.

[0109] Both the monochromatic light-emitting devices in Comparative Example 1 and Experimental Example 1 are blue light-emitting devices. The only difference between the monochromatic light-emitting devices in Comparative Example 1 and Experimental Example 1 is the guest material in the light-emitting layer. The device layer structure, other functional layers, and host material in the light-emitting layer of the first and second blue light-emitting devices in Comparative Example 1 and the third and fourth blue light-emitting devices in Experimental Example 1 are the same.

[0110] Both the first blue light-emitting device in Comparative Example 1 and the third blue light-emitting device in Experimental Example 1 were controlled to operate at the same constant current (50 nm / cm). 2 Electroluminescence tests were performed at the same initial luminescence intensity. The electroluminescence lifetime parameter T10 of the first blue light-emitting device in Comparative Example 1 and the electroluminescence lifetime parameter T11 of the third blue light-emitting device in Experimental Example 1 were obtained. In this example, the electroluminescence lifetime parameter T10... iThe degree of decay in the electroluminescence brightness of a blue light-emitting device over a 200-hour emission period, such as... Figure 9 As shown, Figure 9 The data records the luminance curves of the first and third blue light-emitting devices as a function of luminous time from 0 hours to 200 hours of luminous emission. During the same luminous time, the first blue light-emitting device consistently exhibits lower luminance than the third blue light-emitting device, and its luminance decay is always greater.

[0111] Both the second blue light-emitting device in Comparative Example 1 and the fourth blue light-emitting device in Experimental Example 1 were controlled to operate at the same constant current (50 nm / cm). 2 Photoluminescence tests were performed at the same initial luminescence intensity and under the same second initial luminescence intensity. The excitation wavelength of the light source in the photoluminescence test was 460 nm, which is the optimal absorption wavelength of the emitting layer in the photoluminescence spectrum of the blue light-emitting device. It was also necessary to control the first initial luminescence intensity to be the same as the second initial luminescence intensity. The photoluminescence characterization lifetime parameter T20 of the second blue light-emitting device in Comparative Example 1 and the electroluminescence characterization lifetime parameter T21 of the fourth blue light-emitting device in Experimental Example 1 were obtained. In this example, the photoluminescence characterization lifetime parameter T2... i This refers to the degree of decay in photoluminescence brightness of a blue light-emitting device over a 200-hour emission period, such as... Figure 9 As shown, Figure 9 The data records the photoluminescence brightness of the second and fourth blue light-emitting devices as a function of luminescence time from 0 hours to 200 hours. During the same luminescence time, the first blue light-emitting device consistently exhibits lower brightness than the third blue light-emitting device, and its brightness decay is always greater.

[0112] It should be noted that, as Figure 9 As shown, the initial luminous intensity of the first, second, third, and fourth blue light-emitting devices remained consistent during the test. The electroluminescence characterization lifetime parameter T1 of the blue light-emitting devices in Experimental Example 1 is... i Less than the photoluminescence characterization lifetime parameter T2 i, The electroluminescence characterization lifetime parameter T1 of the blue light-emitting device in Experiment Example 1. i The brightness decay is 1% within 200 hours of emission time, which is within the range of 0% to 2%.

[0113] The lifetime test results of the first blue light-emitting device in Comparative Example 1 and the third blue light-emitting device in Experimental Example 1 are shown in Table 1 below.

[0114] Table 1

[0115]

[0116] In Table 1, vd represents the operating voltage, Y represents the operating voltage value of Experimental Example 1, CIEx and CIEy represent color coordinate values, and BI represents luminous efficiency. BH0 represents the main luminescent material in the luminescent layer of Comparative Example 1 and Experimental Example 1, BD-1 represents the object luminescent material in the luminescent layer of the light-emitting device in Experimental Example 1, and BD-2 represents the main luminescent material in the luminescent layer of the light-emitting device in Comparative Example 1. This comparative experiment uses the object luminescent material in the luminescent layer of the light-emitting device as a single variable for control. LT95 (hrs) represents the luminous lifetime of the light-emitting device, which is the time it takes for the luminous brightness of the light-emitting device to decrease from 100% to 95%. The initial brightness of Experimental Example 1 is the same as that of Comparative Example 1. In Table 1, the luminous lifetime of Experimental Example 1 is taken as the benchmark and set to 100%; therefore, the luminous lifetime of the light-emitting device in Comparative Example 1 is only 60% of that in Experimental Example 1. This further confirms that the luminous lifetime of the light-emitting device selected using the material screening method of the first aspect of the present application is significantly improved compared to that of ordinary light-emitting devices.

[0117] As shown in Table 1, the color coordinates CIEx and CIEy of the light emitted by the first and second monochromatic light-emitting devices are basically the same, and the current efficiencies of the two monochromatic light-emitting devices are also the same. However, the luminous lifetime of the second monochromatic light-emitting device in Experimental Example 1 is 40% higher than that of the first monochromatic light-emitting device in Comparative Example 1. From the above performance test results of the monochromatic light-emitting devices, it can be seen that the light-emitting layer material selected by the material screening method provided in the first aspect of this application can significantly improve the luminous lifetime of blue light-emitting devices.

[0118] The embodiments of the present invention described above are not exhaustive, nor do they limit the invention to the specific embodiments described. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A material screening method for screening light-emitting layer materials of light-emitting devices, characterized in that, The screening method includes: Multiple groups of luminescent materials are configured, each group of which includes a host material and a guest material. Multiple sets of monochromatic light-emitting devices are provided, and each set of light-emitting materials is used as the light-emitting layer material to fabricate multiple sets of monochromatic light-emitting devices with light-emitting layers. Each set of monochromatic light-emitting devices includes the same first monochromatic light-emitting device and second monochromatic light-emitting device. Obtain the electroluminescence characterization lifetime parameter T1 of the first monochromatic light-emitting device in each group of monochromatic light-emitting devices. i Simultaneously, the photoluminescence characterization lifetime parameter T2 of the second monochromatic light-emitting device in each group of monochromatic light-emitting devices is obtained. i ; According to the electroluminescence characterization lifetime parameter T1 corresponding to each group of monochromatic light-emitting devices i and the photoluminescence characterization lifetime parameter T2 i A target luminescent material group is selected from multiple groups of luminescent materials to serve as the luminescent layer material of the luminescent device. Specifically, in obtaining the electroluminescence characterization lifetime parameter T1 of the first monochromatic light-emitting device in each group of monochromatic light-emitting devices... i Simultaneously, the photoluminescence characterization lifetime parameter T2 of the second monochromatic light-emitting device in each group of monochromatic light-emitting devices is obtained. i The steps include: Under the same constant current conditions, the first monochromatic light-emitting device in each group of monochromatic light-emitting devices is controlled to emit light electroluminescence, and the initial luminous brightness of each first monochromatic light-emitting device is controlled to be the same. The second luminous intensity I' of each first monochromatic light-emitting device under the same constant current and the same second luminous time t' is detected and recorded. The electroluminescence characterization lifetime parameter T1 corresponding to each first monochromatic light-emitting device is obtained based on the second luminous intensity I' and the second luminous time t'. i ; In the photoluminescence test, an excitation source with a first preset wavelength is used to optically excite the second monochromatic light-emitting device, and the initial luminous brightness of each second monochromatic light-emitting device is controlled to be the same. The first luminous intensity I of the second monochromatic light-emitting device under the same first luminous time t and the optical excitation of the excitation source is detected and recorded. Based on the first luminous intensity I and the first luminous time t, the photoluminescence characterization lifetime parameter T2 corresponding to the second monochromatic light-emitting device is obtained. i The first emission time t and the second emission time t' are the same.

2. The material screening method according to claim 1, characterized in that, Based on the electroluminescence characterization lifetime parameter T1 corresponding to each group of monochromatic light-emitting devices i and the photoluminescence characterization lifetime parameter T2 i The step of selecting a target luminescent material group from multiple groups of luminescent materials to serve as the luminescent layer material of the luminescent device includes: The electroluminescence characterization lifetime parameter T1 corresponding to each group of monochromatic light-emitting devices is... i and the photoluminescence characterization lifetime parameter T2 i By comparison, those that meet the photoluminescence characterization lifetime parameter T2 are selected. i Less than the electroluminescence characterization lifetime parameter T1 i The groups of luminescent materials corresponding to the monochromatic luminescent devices are used to form a first group of luminescent materials.

3. The material screening method according to claim 2, characterized in that, Characterizing lifetime parameter T1 using standard electroluminescence a One or more target luminescent material groups are selected from the first group of luminescent materials.

4. The material screening method according to claim 3, characterized in that, The light-emitting layer material is a blue light-emitting layer material. The standard electroluminescence characterization lifetime parameter T1 a The value range is 0% to 2%, wherein the standard electroluminescence characterization lifetime parameter T1 a The degree of brightness decay of the monochromatic light-emitting device within a first preset light-emitting time.

5. The material screening method according to claim 4, characterized in that, The standard electroluminescence characterization lifetime parameter T1 a The value range is 1% to 2%.

6. The material screening method according to claim 4, characterized in that, The first preset luminescence time is 200 hours.

7. The material screening method according to claim 3, characterized in that, The light-emitting layer material is either a red light-emitting layer material or a green light-emitting layer material. The standard electroluminescence characterization lifetime parameter T1 a The value range is 0% to 1%, where the standard electroluminescence characterization lifetime parameter T1 a The degree of brightness decay of the monochromatic light-emitting device within a first preset light-emitting time.

8. The material screening method according to claim 7, characterized in that, The first preset luminescence time is 200 hours.

9. The material screening method according to claim 1, characterized in that, In the step of configuring multiple groups of luminescent materials: The main materials included in each group of luminescent materials are the same, while the object materials included in each group of luminescent materials are different from each other.

10. The material screening method according to claim 1, characterized in that, Obtaining the first preset wavelength includes the following steps: A test monochromatic light-emitting device is provided, wherein the test monochromatic light-emitting device and the second monochromatic light-emitting device in each group of monochromatic light-emitting devices have the same device structure and light-emitting color of the light-emitting layer; In the test monochromatic light-emitting device, at least two light-emitting units with different brightness attenuation levels are selected, wherein the light-emitting unit with an attenuation level of 0% is used as the reference light-emitting unit, and the light-emitting unit with an attenuation level greater than 0% is used as the comparison light-emitting unit; In the thickness direction of the test monochromatic light-emitting device, a first cross-section is taken on the device region corresponding to the reference light-emitting unit, and at least the light-emitting layer, electron transport layer and hole transport layer in the reference light-emitting unit are exposed through the first cross-section; Photoluminescence absorption spectroscopy was performed on the first cross-section of the reference light-emitting unit to obtain the optimal absorption wavelengths of the light-emitting layer, electron transport layer, and hole transport layer in the photoluminescence spectrum.

11. The material screening method according to claim 10, characterized in that, The step of obtaining the first preset wavelength further includes: In the thickness direction of the test monochromatic light-emitting device, a second cross-section is taken for the device region corresponding to each of the comparison light-emitting units, and at least the light-emitting layer, electron transport layer and hole transport layer in each of the comparison light-emitting units are exposed through the second cross-section; Photoluminescence tests are performed on the first and second cross-sections along the thickness direction of the test monochromatic light-emitting device using excitation light sources with the optimal absorption wavelengths, respectively, to obtain the photoluminescence intensity of the reference light-emitting unit and each of the comparison light-emitting units. The first preset wavelength is obtained based on the photoluminescence intensity of the reference light-emitting unit corresponding to each excitation light source having the optimal absorption wavelength and the comparison light-emitting unit.

12. The material screening method according to claim 11, characterized in that, The step of obtaining the first preset wavelength based on the photoluminescence intensity of the reference light-emitting unit and the comparison light-emitting unit corresponding to each excitation light source having the optimal absorption wavelength includes: The photoluminescence intensity of the reference light-emitting unit and the comparison light-emitting unit corresponding to each excitation light source with the optimal absorption wavelength are compared, and the optimal absorption wavelength corresponding to the largest difference between the photoluminescence intensity of the reference light-emitting unit and the comparison light-emitting unit is selected as the first preset wavelength.

13. The material screening method according to claim 1, characterized in that, The first preset wavelength is the optimal absorption wavelength of the light-emitting layer in the photoluminescence spectrum.

14. A light-emitting device, characterized in that, include: The light-emitting layer has a light-emitting host material and a light-emitting object material; The photoluminescence characterization lifetime parameter T2 of the luminescent object material i Less than the electroluminescence characterization lifetime parameter T1 i , And the electroluminescence characterization lifetime parameter T1 i Less than the standard electroluminescence characterization lifetime parameter T1 a The standard electroluminescence characterization lifetime parameter T1 a The value range is 0% to 2%, wherein the standard electroluminescence characterization lifetime parameter T1 a The degree of brightness decay of the light-emitting device within a first preset light-emitting time; Among them, the photoluminescence characterization lifetime parameter T2 of the luminescent object material i Electroluminescence characterization lifetime parameter T1 i The material screening method as described in any one of claims 1 to 13 is used for calculation.

15. The light-emitting device according to claim 14, characterized in that, The standard electroluminescence characterization lifetime parameter T1 a The value range is 1% to 2%.

16. The light-emitting device according to claim 14, characterized in that, The first preset luminescence time is 200 hours.

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